Monday, June 30, 2008
Japanese Stiltgrass has pale green, lance shaped leaves (broader in the middle) about 3 inches in length that alternate along a branched stalk. The leaves also have a stripe of reflective hairs down the middle that are silvery in appearance. Seed heads are thin spikes and seed production occurs from September to frost (mid October). Seeds germinate earlier than crabgrass in March or April.
Japanese stiltgrass. Photo by Susan Barton, UD Extension Ornamental Horticulture Specialist.
It is critical to stop Japanese stiltgrass from going to seed in September. Mowing is often effective but must be very short and just before flowering to avoid reseeding. Glyphosate herbicide is effective but is non-selective. Acclaim extra (fexoxaprop-p-ethyl) has given good control as a postemergence herbicide, is more selective, and is an option for turfgrass and wooded areas. In contrast, research has shown that dithiopyr and quinclorac applied postemergence were ineffective on Japanese stiltgrass in turf. Research by Judge, Neal, and Derr (NC State and VPI) has also shown that single postemergence applications of the grass herbicides clethodim, fluazifop-P, or sethoxydim controlled Japanese stiltgrass 50 to 88%. These herbicides applied twice provided 82 to 99% control. These are options in landscape beds, wooded landscapes, and non-grassed areas. Japanese stiltgrass may also be controlled with early spring applied pre-emergence materials (target 2 weeks before crabgrass). The same research showed that benefin plus oryzalin, dithiopyr, isoxaben plus trifluralin, oryzalin, oxadiazon, pendimethalin, prodiamine, or trifluralin applied preemergence controlled Japanese stiltgrass 87% or greater 8 weeks after treatment.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
A very common weed in this situation is marestail (Conza canadensis), also known as horseweed, a winter annual that overwinters as a rosette type of growth and then sends up a large stem and flowerstalk during the following summer. Marestail produces large amounts of light fluffy seed and can travel long distances. It also is common in un-mowed roadsides and waste areas. Mowing is effective in controlling the stem phase of marestail but not the rosette phase. Herbicides that control marestail in turf include 2,4-D, clopyralid (Lontrel) and others in the growth regulator category. In landscape beds, clopyralid (Lontrel) can be used in some situations for control, isoxaben (Gallery) has preemergence activity, and herbicides containing oxyfluorfen (Goal, Rout, OH2) also provide good control. An important issue to note is that there are glyphosate resistant strains of marestail in Delaware so Roundup and similar products may give little or no control in some cases. Canada thistle (Cirsium arvense), a noxious weed regulated by the Delaware Department of Agriculture, can also build up in these vacant sites. It is a perennial weed that can spread by the light, fluffy seed produced in late spring or early summer, as well as by underground rhizomes. Glyphosate spot sprayed is most effective in controlling Canada thistle in the fall or when it is in bud (late May or early June). Glyphosate is relatively ineffective when Canada thistle is growing vegetatively in the spring or after regrowth from rhizomes in summer. Triclopyr containing herbicides are highly effective on Canada thistle in turf (Turflon, Confront, others).
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
Sunday, June 29, 2008
Microbial pesticides have become much more available than in decades past for two reasons. Microbial pesticides can be considered natural (as long as the microorganism has not been genetically engineered), and so they are permitted for use in organic agriculture. Organic agriculture has grown substantially in recent years, creating market demand for these products.
Microbial pesticides are often perceived as safer to the environment than conventional chemical pesticides. For the most part, this perception is justified for several reasons: microbial pesticides are less toxic to non-target organisms (beneficial organisms, for example), more specific to target organisms (the pests and disease-causing pathogens), and often quicker to degrade than conventional chemical pesticides. However, because of these qualities, microbial pesticides may need to be applied more frequently than modern chemical pesticides, and simply running the tractor through the field frequently has its own environmental cost.
Plant pathologists from The Ohio State University have published a fact sheet on microbial pesticides, entitled Microbial Biopesticides for the Control of Plant Diseases in Organic Farming, available online at http://ohioline.osu.edu/hyg-fact/3000/pdf/HYG_3310_08.pdf. This short publication is a very nice piece of work. After an introduction, the publication lists the commercial microbial pesticides labeled for controlling bacterial diseases (=bactericides) and fungal diseases (=fungicides). The publication also lists the diseases each product is labeled for, and the efficacy of that product based on independent research.
Because microbial pesticides are selective for certain target diseases, growers who are knowledgeable about crop diseases have the best chance of using them successfully. Growers need to know which diseases pose a risk to their crops, so that they can select a product that will work.
Although the active ingredients of microbial pesticides pose a low risk to the environment, these products are often less effective at controlling diseases than modern chemical pesticides. This is not an indictment against these products, but simply an attempt to assure that expectations for efficacy of these products are realistic.
Information from the June 23, 2008 edition of the Kentucky Pest News from the University of Kentucky College of Agriculture.
White Grubs - There is no reliable way to predict whether any given year will be a bad one for white grubs - the immature, turf-feeding stages of Japanese beetles, masked chafers, and certain other beetles (May beetles, green June beetle,, Oriental beetle, European chafer, Asiatic garden beetle).
Indicators of Infestation- White grubs and their resultant damage are not usually evident until August or September. Although sampling the turf is the only way to confirm that grubs are present, certain factors may indicate an increased risk of infestation later in the season. If your turf has a history of serious grub problems, there is a greater chance that adult beetles will return and re-infest the same areas. Sites with large numbers of adult beetles in June and July are more likely to have grubs in late summer. Early warning signs include swarms of brown, ½-inch long masked chafer beetles skimming over the turf at dusk, large numbers of adult Japanese beetles in the landscape, or green June beetles buzz-bombing the turf by day in search of mates and egg-laying sites. Masked chafer adults are also attracted to porch and streetlights at night.
Rainfall and soil moisture are critical factors affecting the extent of grub damage during a season. Frequent irrigation in June and July may attract egg-laying female beetles to the turf, especially if surrounding areas are dry. High soil moisture also increases egg survival. If lawns are irrigated during periods of dryness in June and July, be especially alert for signs of grubs later in the summer. Conversely, adequate soil moisture in August and September (when grubs are actively feeding) can help to hide root injury. Irrigated turf can sometimes tolerate 20 or more grubs per square foot before showing signs of injury.
Treatment Strategies - Two different strategies are available for controlling white grubs with insecticides: preventive and curative. Each approach has its own merits and limitations. With preventive control, the insecticide is applied as insurance, before a potential grub problem develops. Consequently, preventive control is best suited for high-risk sites with a history of grub problems, or turf sites where heavy beetle activity is noted.
Preventive control requires the use of insecticides with long residual activity in soil. Look for products containing the active ingredient imidacloprid (e.g. Merit®, Bayer Advanced™ Season-Long Grub Control, Scott's GrubEx), halofenozide (e.g. Mach 2®), clothianidin (Arena®), thiamethoxam (Meridian®), or chlorantraniliprole (Acelepryn ). Those ingredients have sufficient soil persistence to apply anytime from now (mid-June) to late-July and still control young grubs hatching from eggs from mid-July to early August. The optimum treatment period for these products is mid-June to mid-July.
Preventive treatments afford greater flexibility in application timing, and are easier to schedule and implement than are curative treatments. They often afford greater peace of mind to golf superintendents and lawn service companies because potential damage is avoided or minimized. The main drawback of preventive grub control is that the decision to treat must be made before knowing the extent of infestation. Grub outbreaks tend to be localized and sporadic and only a small percentage of lawns require treatment in a given year. Thus, preventive control often results in areas being treated unnecessarily. Good record keeping and observation will help in pinpointing grub-prone areas, which are the most logical candidates for preventive applications.
With curative control, treatment is applied in late summer - typically August or September - after the eggs have hatched and grubs are present. Ideally, the decision to treat is based on site inspection and sampling or past history of infestation. Since white grub infestations tend to be localized, the entire lawn often will not need to be treated. Grub "hot spots," which can be confirmed by sampling, are most likely to be full sun, south or west-facing slopes, lawns seeded with Kentucky bluegrass, lawns that were heavily irrigated during June and July, and turf areas that were damaged by grubs in previous years.
Proper timing of curative grub treatments can be tricky. Insecticides applied before early August may degrade before the eggs have hatched, whereas if the product is applied in late August or September, the grubs will be large and harder to kill and severe damage to turf may have already occurred. Granular formulations containing the active ingredient trichlorfon (e.g. Dylox) are the fastest-acting, most effective insecticides for curative grub control. Carbaryl (Sevin) can also be used. There is little benefit in applying a short-lived, curative-type product for white grubs in June or July.
Information from the June 23, 2008 edition of the Kentucky Pest News from the University of Kentucky College of Agriculture.
Saturday, June 28, 2008
Porcelain-berry (Ampelopsis brevipedunculata) is a deciduous, woody perennial climbing vine. A member of the grape family (Vitaceae) it is a native of northeast Asia and was originally brought to the United States in the late 1800’s for use as a landscape plant. The plant is hardy and well adapted to a variety of environmental conditions, growing in dry to moist areas in full sunlight to partial shade. The vigorous vines of porcelain-berry are relatively insect and disease resistant and out compete other vegetation by reducing the availability of light and other resources required for growth. This aggressive growth pattern results in dense porcelain-berry thickets that smother near-by trees and shrubs. Porcelainberry is now found from New England to North Carolina and west to Michigan and is considered “invasive” in twelve northeastern states including Delaware where it has been identified in all three counties.
Porcelain-berry. Note that the berry is hard when ripe whereas wild grapes are soft.
Once established, porcelain-berry is often difficult to remove. Porcelain-berry seeds are deposited by birds that eat the berries, giving rise to new plants. In addition, porcelain-berry spreads by a process known as “layering” in which roots form when the stems of a plant are in contact with soil and extensive root systems are created. Manual control is difficult because of the extensive root system. Be aware that the roots could be entwined with the roots of desirable species, which could be damaged when porcelain-berry is pulled out by its’ roots. Plants should be pulled by early spring to prevent flower bud formation. In the fall, plants should be pulled before fruiting to prevent the production and dispersal of seeds. If manual control is not feasible, porcelain-berry may be controlled by chemical methods. Spot applications of a glyphosate herbicide are effective. Glyphosate is a nonselective herbicide that kills all exposed vegetation. Thus it is important to avoid contact with desirable plants. Cut stems may also be treated with a glyphosate herbicide. Herbicide treatment is most effective when applied toward the end of the growing season (September and early October) when plants are actively transporting nutrients from the stems and leaves to the roots. Follow up treatments for both manual and chemical control will be needed for several years until no porcelain-berry remains.
Go to http://www.cityofmilford.com/pb/pbfactsheet.pdf to view the full factsheet on this invasive plant.
Japanese maple scale is being found currently in nurseries and landscapes. Check in your area for crawlers. We have found this scale on maples, zelkova, holly, styrax, yellowwoods, and many other woody plants. This scale is tiny (< 0.5 mm) and has an elongate white cover and is found on the bark and branches of its hosts. This scale has two generations that overlap because eggs hatch over an extended period of time. Controlling this scale is challenging because new crawlers are emerging and present over an extended period of time.
Control: Distance or Talus can be applied now. A 2% horticultural oil can also be used but repeated applications may be necessary. Since this scale is difficult to control and has 2 generations of potentially overlapping adults, consider waiting another week to 10 days for more eggs to hatch to provide better control.
Information taken from the June 27, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from University of Maryland Cooperative Extension.
Friday, June 27, 2008
Hydrangea umbellata, the umbel hydrangea, is a early blooming lace cap type Hydrangea that is cold hardy and also heat tolerant and sun tolerant. The following are some pictures from the Scott Arboretum at Swarthmore College in Pennsylvania.
Go to http://blogs.scottarboretum.org/gardenseeds/2008/06/hydrangea-umbellata/ for more information on this species from the Scott Arboretum.
Landscape Horticulture and Design is a new major in the University of Delaware's Department of Plant and Soil Sciences. It fuses the creative aspects of art and design with the technical and scientific aspects of horticulture. These two unique but equally rewarding fields encompass the analysis, planning, design, implementation and management of natural and built environments, as well as the value of plants in public settings. Technology plays an important role in landscape horticulture and design – allowing today’s professionals to use advanced tools to map out projects, perform detailed analyses, run businesses efficiently, broadly interpret plant collections and displays for the public and quickly revise and update designs and business plans.
Go to http://ag.udel.edu/plsc/lsDesign/index.html for more information
Thursday, June 26, 2008
The golden rain tree (Koelreuteria paniculata) is an excellent tree for small areas. It has a nice rounded outline, dark green foliage that turns a golden yellow in the fall, and flowers in the middle of summer. The golden rain tree flowers are bright yellow and are held in a large foot long panicle so it is impossible to miss the sunny colors. After flowering, the fruit that is formed is shaped like an old fashioned lantern and starts out a soft yellow color that slowly changes to brown. Because the tree grows only 20 to 40 feet high and is very adaptable to many soil conditions and air pollution it is often planted as a street tree. There are not a lot of insect or disease problems associated with the golden rain tree.
Information from the August 17, 2007 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.
Brown patch may become very active now after ther rain and humidity in parts of southern Delaware. This disease, caused by the fungus Rhizoctonia solani, will likely start showing up soon. To reduce the incidence and severity of brown patch for golf courses and other highly managed turf, avoid large applications of quick release nitrogen sources (e.g., not more than ¼ lb actual N/1000 sq. ft) during hot weather, irrigate between midnight and 8 a.m. to minimize the leaf wetness period, and spray turf now with Armada,, Chipco 26GT, chlorothalonil, Compass, ConSyst, Curalan, Eagle, Endorse, Headway, Heritage, Insignia, mancozeb, Medallion, Prostar, Spectro, Tartan, thiophanate-methyl, or Touche per manufacturer's recommendations. Homeowners should avoid summer applications of nitrogen. For most residential situations, brown patch causes a blight of the leaves but does not kill the plants and the lawn recovers when the weather changes.
Information from Bob Mulrooney, Extension Plant Pathologist, UD.
Wednesday, June 25, 2008
Foliar nematodes (Aphelenchoides spp.) have become a more common pest in herbaceous perennials over the past few years. Foliar nematodes move in films of water on plant surfaces and enter leaf tissues through natural openings in leaves called stomates. Like root-attacking nematodes, foliar nematodes have a needle-like structure called a stylet that they use to pierce plant cells and feed on the cell contents, resulting in cell death. Lesions caused by foliar nematodes are first chlorotic, then necrotic. Movement of the nematodes within leaf tissues is restricted by larger leaf veins, which gives the lesions their typical angular shape (see figures).
Foliar nematodes overwinter in plant debris. They survive for long periods of time in leaf tissues, and are spread by propagating infested plants and by splashing water (rainfall, overhead irrigation). The list of plants susceptible to foliar nematodes is quite large, and includes woody plants like azaleas as well as numerous herbaceous perennials (such as chrysanthemum, hosta, hellebores, ferns, begonias, salvia, anemone). The easiest way to manage foliar nematode problems is to avoid introducing the pest into the garden. Carefully inspect plants for foliar nematode symptoms before planting. If symptoms develop, remove and destroy affected plants.
Premature dying of foliage in the garden is symptomatic of foliar nematode but is easily overlooked or misidentified. Constant leaf wetness helps nematodes as they swim in a film of water and enter the leaves through stomata. Remove infected leaves and destroy them. We still do not have any effective chemical controls for the home or commercial landscape.
Information from Karen Rane, Plant Disease Diagnostician, Department of Botany & Plant Pathology, Purdue University and Bob Mulrooney, Extension Plant Pathologist, UD.
Different species of leafminers feed upon different plants. Leafminers may be either wasp, fly, moth or beetle species. One of the more common leafminer species is Liriomyza trifolii that infests many floral and vegetable crops, especially members of the Compositae family. This species attacks chrysanthemum, and gerbera daisy. It caused serious problems in the cut mum industry in the 1980's and was notoriously difficult to control.
Growers of garden mums should be on the lookout for the damage caused by this species. Look for narrow mines that wind around the leaves, with some brown tip dieback. Herbaceous perennial growers have also noted seeing Liriomyza leafminer damage on Helenium, Leucanthemum, and Gaillardia as well as others in recent years.
Adult leafminer flies puncture holes in the leaves as they lay eggs. Look for white specks from these egg laying punctures. (See photo). Leafminer adults may be confused with shore fly adults. However, adult serpentine leafminer flies have yellow markings on their abdomen whereas shore flies do not. With a hand lens, you can also see a cannon-shaped ovipositor or egg-laying device on the females rear end.
As the larvae feed, winding (serpentine) mines develop. Leafminer larvae are in a protected location as they feed between the upper and lower leaves making control difficult. If only a few plants are affected, removal of infested plants or leaves may help. Some greenhouse growers use yellow sticky tape or ribbon to help mass trap out leafminer adults. Once larvae are inside the mines, often insecticides with systemic or slightly systemic (translaminar) activity work best such as acephate (Orthene).
Information from the New England Greenhouse Update.
Tuesday, June 24, 2008
Many woody plant species are susceptible to Verticillium wilt. In Delaware, we see this disease most often on maple and tulip trees. Plants that are immune or somewhat resistant to Verticillium wilt are those that limit the spread of the pathogen in the plant. These species include all gymnosperms (needled evergreens) and all monocots (grasses, sedges, rushes, lilies).
Susceptible to Verticillium: ash, azalea, boxwood, brambles, buckeye, catalpa, cherry and other stone fruits, Kentucky coffee tree, currant and gooseberry, elm, golden-rain tree, hibiscus, honeysuckle, horse-chestnut, India-hawthorn, lilac, black locust, magnolia, maple, Russian olive, osage orange, osmanthus, Japanese pagoda tree, peony, persimmon, photinia, privet, redbud, rose, sassafras, serviceberry, smoke tree, spirea, sumac, tree-of-heaven, tulip tree, viburnum, wiegela, and yellowwood
Resistant to Verticillium apple and crabapple, beech, birch, boxwood, butternut, dogwood, eucalyptus, firethorn, hackberry, hawthorn, hickory, holly, Katsura tree, linden, honey locust, mountain ash, mulberry, oak, oleander, pawpaw, pear, pecan, plane tree and sycamore, poplar, quince and flowering quince, rhododendron, sweet gum, walnut, willow, and Japanese zelkova.
Information from Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University.
Although there does not seem to be a single cause for the decline and death of landscape maples, most of the causes would be exacerbated by the 2007 drought. In addition to drought, there have been a number of factors observed that have caused death or triggered decline and death of maples, including:
• Girdling roots are probably the leading cause of decline, especially among Norway maples. Offending roots may not be visible above ground, but if the tree trunk does not have the normal buttress root flare at the base, and instead, goes straight into the ground like a telephone pole, self-girdling roots can be suspected. Trees with girdling roots may decline over a period of years, but then may collapse suddenly. Girdling roots are often a response to too-deep planting, often two or three decades or more after the tree was transplanted.
• Verticillium wilt may infect all types of maples, and can also cause disease in tuliptrees, catalpas, golden-rain trees, and redbuds. Often developing on branches on one side of the tree first, leaves progressively wilt and die throughout the tree during the growing season. Where infections occurred late in the previous season, trees may not have even leafed out this year, or if they did, they immediately died. The Verticillium fungus is often more active in stressed trees. Large trees may die over a year or two, but small trees can suddenly collapse throughout from Verticillium wilt.
• Bacterial leaf scorch can affect many kinds of maples, but appears to be most common on red maples. This chronically infectious disease could weaken trees and make them vulnerable to other stresses.
• Canker and collar rot. We have diagnosed some cases of Phytophthora bleeding canker and collar rot on maples in past years. Trunks of affected trees have water-soaked bark spots. Collar rot, causing bark decay and wood staining, if well developed, can cause death of the top of the tree. Usually, collar rots and bleeding cankers lead to gradual decline of infected trees. The microbe that causes the disease, Phytophthora, is favored by high soil moisture levels, especially temporary flooding.
• Restricted rooting space. Sugar maples planted as street trees sometimes lack space for their roots to exploit. Such trees with inadequate root systems would be especially vulnerable to drought and temporary flooding stresses. Trees growing where there is plenty of open space but on shallow soils with bedrock near the surface will be vulnerable to drought.
• Soil compaction from foot traffic, construction, or other activities crushes small roots and makes soils impervious to invasion by new roots. Affected maples may decline.
• De-icing salts used the previous winters can sometimes be a factor in tree decline.
• Mechanical injuries. Construction such as laying utilities severs roots and triggers decline. Wounds to the trunk or large branches can also have negative effects on maple tree health.
• Opportunistic fungi. Root, butt, and trunk rotters such as Armillaria mellea and Ganoderma lucidum are found on some declining trees. In addition, canker and canker-rot fungi such as Botryosphaeria obtusa, Nectria cinnabarina, Cerrena unicolor, and Stegonosporium pyriforme are capable of invading weakened trees and causing branch dieback.
Adapted from "SUDDEN DEATH OF MAPLES IN THE LANDSCAPE" By John Hartman in the Kentucky Pest News from the University of Kentucky.
Monday, June 23, 2008
Tractor loaders are helpful for moving materials from one place to another. However, a fully loaded loader makes the tractor front heavy and could cause an accident. Only install loaders designed specifically for the tractor to reduce the chances of rollover or malfunction. A raised loader changes the center of gravity of the tractor and can cause the tractor to tip under conditions that would normally be safe. Also, tractor loaders often operate in confined areas that make short turns unavoidable. Both of these factors make loader-equipped tractors susceptible to rollovers.
To Avoid a Rollover
• Watch carefully for obstructions and depressions.
• Handle the rig smoothly, avoiding quick starts, stops, and turns.
• Keep the bucket as low as possible when turning and transporting.
• Ballast the tractor loader combination as recommended by the manufacturer. Or, attach wheel weights to the rear axles or wheel rims. Weight may also be carried by a three-point hitch.
• Adjust the width of the tractor as wide as practical or possible.
• Use a front end loader only for its specific purpose. It should not be used for removing fence posts, towing, or knocking something down.
Other Tractor Loader Safety Tips
• No riders on the tractor!
• Lower loader arms slowly and steadily.
• Keep travel speed slow.
• When turning, adjust for the extra length of the loader.
• Raise the loader in an area free of overhead obstacles, such as overhead power lines.
• Keep the loader low while carrying loads and/or while driving on an incline.
• Use special care when driving over uncompacted soil, which can be unstable.
• Drive loaded buckets uphill rather than downhill, and stay off steep slopes to prevent bouncing and loss of control.
• Back filling (replacing dirt) can cause new construction areas to collapse.
• Watch for falling rocks and cave-ins when undercutting.
• Stay away from the outer edge of banks and slopes.
• Load the bucket evenly from side to side and keep within the normal capacity of the tractor and loader.
• Use the recommended amount of ballast to give the tractor extra stability.
• Never tow a tractor by attaching a tow chain or cable to the loader.
• Never allow people to ride in the bucket.
• A load should not be moved or swung with people in the work area.
• Operate controls only when seated on the tractor.
• Remove the loader from the tractor when the loader is not in use.
• Physically block the bucket and/or arm if they have to be raised for maintenance.
• Never walk or work under a raised loader.
• Put the loader on the ground, turn off the engine/electric power, then dismount.
• Be sure the tractor has back-up alarms in case the driver’s view to the rear is blocked.
Information from Tailgate Safety Training for Landscaping and Horticultural Services from the Ohio State University.
Landscape Plants Seldom Damaged by Adult Japanese Beetles.
Scientific name - Common name
Acer negundo - Boxelder*
Acer rubrum - Red maple
Acer saccharinum - Silver maple
Buxus sempervirens - Boxwood
Carya ovata - Shagbark hickory*
Cornus florida - Flowering dogwood
Diospyros virginiana - Persimmon*
Euonymus species - Euonymus (all species)
Fraxinus americana - White ash
Fraxinus pennsylvanica - Green ash
Ilex species - Holly (all species)
Juglans cinerea - Butternut*
Liriodendron tulipifera - Tuliptree
Liquidamar styraciflua - American sweetgum*
Magnolia species - Magnolia (all species)
Morus rubra - Red Mulberry
Populus alba - White poplar
Pyrus communis - Common pear*
Quercus alba - White oak*
Quercus coccinea - Scarlet oak*
Quercus rubra - Red oak*
Quercus velutina - Black oak*
Sambucus canadensis - American elder*
Syringa vulgaris - Common lilac
>>Most evergreen ornamentals, including Abies (fir), Juniperus, Taxus, Thuja (arbor vitae), Rhododendron, Picea (spruce), Pinus (pine) and Tsuga (hemlock) are not attacked.
*Species marked with an asterisk may suffer occasional light feeding.
Information from "JAPANESE BEETLES IN THE URBAN LANDSCAPE" by M.F. Potter, D.A. Potter, and L.H. Townsend, University of Kentucky.
Sunday, June 22, 2008
There are many growers of garden mums in Delaware. This is a good income generating crop for the fall period. Growing good mums requires keeping on top of pests including diseases. The following is information on diseases to watch for in garden mum production.
Common diseases diagnosed in recent years have been root rots caused by Pythium and Rhizoctonia and bacterial leaf spot (Pseudomonas cichorii). Fusarium wilt occurs when cuttings are infected or soil is contaminated with the pathogen. Leaf spots caused by Alternaria, Botrytis and Septoria are not common on mums but occur ocassionally. White rust (Puccinia horiana), also not common, has shown up in the Northeast in recent years.
Mums suffering from root diseases will often look nutrient deficient and they are, considering the roots are not functioning correctly. Plants with root rot often look stunted, wilted and have veinal reddening even when adequate nutrition is being applied. Fungicide drenches for root rots include, thiophanate methyl & etridiazole (Banrot) for Pythium and Rhizoctonia; mefenoxam (Subdue MAXX), etridiazole (Truban) propamocarb (Banol) for Pythium; and fludioxonil (Medallion), thiophanate methyl (Cleary's 3336, Fungo Flo) or iprodione (Sextant) for Rhizoctonia.
Fusarium is a vascular disease that develops within stems. Fusarium wilt results in symptoms similar to root rot but plants infected with Fusarium generally wilt in sectors, or one branch at a time and roots often appear healthy. Root rot usually results in the entire plant wilting. In later stages of Fusarium wilt, a white or pinkish fluffy mold may develop on the affected stems. Managing Fusarium centers on disease-free cuttings and pathogen-free root media. Thiophanate methyl (Cleary's 3336) and fludioxonil (Medallion) have been reported to suppress Fusarium.
Bacterial leaf spot, caused by Pseudomonas cichorii often occurs during hot humid weather in August. This disease tends to be problematic during years of heavy rains or where overhead watering is practiced. Plants with this disease have large black spots concentrated at the base of the plant. The spots often begin at the leaf margin but may also occur randomly. From the leaf, the bacterium can move through the petiole and into the stem resulting in a canker. The sepals of infected flower buds will become brown to black and up to several inches of pedicel may be killed. Copper hydroxide sprays such as Kocide 101 77 WP or Phyton 27 will help protect against this disease. These materials do not cure the disease, they limit spreading to uninfected plants. Also there are differences in cultivar susceptibility. Make notes when you see susceptible varieties and avoid growing them in the future.
Alternaria, Botrytis and Septoria can be managed using thiophanate methyl (Cleary's 3336), iprodione (Sextant), chlorothalonil (Daconil Ultrex, Pathguard 6F), chlorothalonil & thiophanate methyl (Spectro 90 WDG) or fludioxonil (Medallion). As the plants grow rapidly in August and develop a dense canopy of leaves, treatments may be necessary. White rust (Puccinia horiana) is a federally quarantined pathogen. Look for white to yellow spotting on the upper sides of the foliage with corresponding pustules of white spores which look bumpy on the undersides of leaves. Cooler weather conditions in fall tend to favor this disease. Although not a common disease, be aware of it. Materials used to protect against rust contain chlorothalonil (Daconil Ultrex, Pathguard 6F), mancozeb (Dithane T/O), azoxystrobin (Heritage), trifloystrobin (Compass), propiconazole (Banner Maxx) and triadimefon (Bayleton). Bacterial leaf spot and foliar diseases are spread by splashing water, which is why we see more of these diseases during rainy years. Drip irrigation helps to prevent foliar diseases. If overhead watering, foliage should always be dry before evening hours.Reprinted from "Garden Mums - Past Crop Problems and Production Tips" by Tina M. Smith, Extension Floriculture Program, UMASS.
Southern red mites are active at this time. Examine broadleaf evergreens including hollies, laurels, camellias, and azaleas. The southern red mite is also commonly found Clethra, Photinia, Pyracantha and Viburnum. If your customers have ornamental or fruit bearing plums and peaches, southern red mite is active on these plants also.
Control: Early in the season some of the best control measures involve using mite growth regulators that impact nymphs of spider mites. These materials prevent mites from shedding their skin and going to the next life stage. Here are some of the mite growth regulators available: hexythiazox (Hexygon), clofentezine (Ovation), etoxazole (Tetrasan). Another miticide that is relatively new that looks very good is Forbid. The chemical in Forbid is translaminar and desiccates treated mites and eggs. It acts a little like a growth regulator in that it inhibits molting of the mites. It also inhibits oviposition in adult females. Some of the other materials for mite control are abamectin (Avid) fenpyroximate (Akari), bifenazate (Floramite), spinosad (Conserve), and pyridaben (Sanmite).
Information from the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension
Saturday, June 21, 2008
Flammable liquids and gases – Gasoline, diesel fuel, degreasing fluids, and paint solvents are flammable materials that are used on by horticultural firms. The vapors from these materials can be extremely explosive in the presence of flames, sparks and hot surfaces. Dangerous practices include fueling a running or hot engine, smoking when handling gasoline and using gasoline as a solvent or cleaning agent. Remember to store flammable products in their original containers in a cool place and out of the sun. Keep cleaning rags in a metal container to reduce the risk of a fire.
Motorized Machinery and Equipment – Fires involving machinery can be costly. Common causes of such fires include defects in the ignition system, leaking fuel lines, improper refueling, smoking, overheated engine, sparks from the exhaust and friction. Common sense preventive measures can reduce these mishaps significantly. When refueling, turn off the engine and extinguish smoking materials. Watch for and repair leaks in fuel lines, carburetors, pumps, etc. promptly. Always work in a well-ventilated area when using solvents and other flammable materials. Be extremely cautious when welding and cutting that sparks are contained and combustible materials are protected from the heat. Take a few minutes to clean dust and plant residue away from the engine and exhaust system of equipment when a build-up occurs.
Lack of fire extinguishers and training - In many cases, fire extinguishers are not carried by horticultural firms. Lack of fire extinquishers or improperly sized fire extinguishers in trucks and on equipment is a problem that is often compounded by users who do not understand the proper use of the extinguisher. Keep fire extinquishers in trucks, on tractors, and on larger motorized equipment (larger mowers). Check with the fire service or equipment manufacturer in regards to the proper size extinguisher, train operators on proper use, and regularly check extinguishers to keep them current and charged.
Information adapted from an article by Ron Jester; Extension Safety Specialist (retired), UD.
Acer palmatum, Japanese maple
Acer platanoides, Norway maple
Aesculus hippocastanum, Horsechestnut
Althaea rosea, Hollyhock
Betula populifolia, Gray birch
Castanea dentata, American chestnut
Hibiscus syriacus - Rose-of-Sharon, Shrub Althea
Juglans nigra, Black walnut
Malus species, Flowering crabapple,
Platanus acerifolia, London planetree
Populus nigra italica, Lombardy poplar
Prunus species - Cherry, black cherry, plum, peach, etc.
Rosa species, Roses
Sassafras albidum, Sassafras
Sorbus americana, American mountain ash
Tilia americana, American linden
Ulmus americana, American elm
Ulmus procera, English elm
Vitis species, Grape
Information from "JAPANESE BEETLES IN THE URBAN LANDSCAPE" by M.F. Potter, D.A. Potter, and L.H. Townsend, University of Kentucky
Friday, June 20, 2008
Many growers will be potting up garden mums and it’s a good time to revisit your fertilizer program. Mums are heavy feeders during the first few weeks. After flowers are formed, nutrient demand diminishes. Your fertilizer program and fertilizer selection should be based on irrigation water quality, so have your irrigation water tested if it hasn’t been done and conduct regular soil tests to monitor soil fertility.
There are several ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release. To start plants off right and prevent premature buds:
Use moistened soil when potting up plants, then water-in freshly planted cuttings with a fertilizer solution containing 200 to 300 ppm of 20-20-20 immediately after planting. The cuttings will establish faster and grow more rapidly.
Do not stress the young plants during their first 4 to 5 weeks of growth, especially during the first 10 days of the crop. Keep plants moist, well fertilized and properly spaced.
Check plant roots regularly to monitor plant health.
To encourage soft growth that branches freely, use 250-300 ppm 20-20-20 or a fertilizer that is at least 60% ammonical nitrogen as a constant feed during the first 2-3 weeks for all fertilizer programs. If using controlled-release fertilizer, keep in mind that its rate of release is affected by its formulation (rate of release), soil temperature and frequency of irrigation. Most formulations release at temperatures of 70°F or above, therefore during cold temperatures of late spring/early summer temperatures, fertilizer is going to be slow to release, when plants need the most fertilizer. This is why liquid feedings become important, to get plants moving and create vegetative growth. Liquid feeds of at least 60% ammonia forms of nitrogen, combined with no water stress, are important to minimize premature budding!
Examples of Fertilizer Programs for Garden Mums
1) 100% Water Soluble Fertilizer Using Drip Irrigation
After plants are established using 20-20-20 the first few weeks, switch to 200-250 ppm of 20-10-20 constant feed for 3-4 applications and then rotate to a calcium nitrate based fertilizer such as 15-0-15 for 1 application, then repeat. Once plants start to show color, reduce to 100 ppm constant feed.
2) Combination of Water Soluble Fertilizer and Low Rate of Controlled Release Fertilizer
Use 250 ppm of 20-20-20 at time of planting and constant feed for first two weeks then change to 20-10-20, 300 ppm once per week and use clear water from first color until sale.
Information from the June 5, 2008 edition of the New England Greenhouse Update. http://www.negreenhouseupdate.info/greenhouse_update/index.php
Liriope and mondo grass are widely used ground covers in the United States. There are approximately five species of liriope, but the two most popular in the ornamental industry are Liriope muscari (Blue Lily-turf) and Liriope spicata (Creeping Lily-turf). L. spicata has a narrower leaf and tends to spread more aggressively than L. muscari. L. muscari is more common in the south, and is not as aggressive as L. spicata, tending to form tighter vegetative clumps.
There are approximately three species of mondo grass, with the most popular being dwarf mondo grass (Ophiopogon japonicus). Mondo grass is closely related to liriope and often confused with liriope. When compared to liriope, mondo grass tends to have narrower leaves and metallic blue fruits, and flowers are usually tucked into the foliage.
Both liriope and mondo grass have very similar growth requirements, with both genera being well adapted to handle a wide variety of growing conditions. Both liriope and mondo grass can grow in fairly deep shade or full sun, and both are just about immune to drought. Most species of liriope and mondo grass have several named cultivars, and will eventually form a solid cover. When this occurs there is very little need for weed control, but between the time you plant liriope or mondo grass and the time you get solid planting, weeds will be a problem.
Many things can be done to help reduce weed problems. First and foremost is bed preparation. If you are planting into a new area, eliminate all vegetation with an application of a broad spectrum herbicide such as glyphosate (i.e., Roundup®) or glufosinate (i.e., Finale®). The bed should then be fertilized (e.g., 1 lb nitrogen/1,000 ft2) and cultivated.
After planting liriope or mondo grass, apply a 2- to 4-inch layer of mulch to the planting area to help prevent weed growth. Encouraging vegetative growth will help attain a solid cover more quickly.
Both liriope and mondo grass will thrive with at least a yearly application of mulch and fertilizer. If possible, water when soil conditions are extremely dry. To encourage spreading, mow liriope or mondo grass to 2-3 inches early in spring before applying an application of fertilizer and mulch. Preemergent herbicides can also be used at this time to help prevent weed growth; refer to Table 1.
Most of these preemergent herbicides are labeled for several species of liriope (i.e., gigantea, muscari and spicata) or mondo grass (i.e., japonicus, jaburan, planiscapus), but some are not! Make sure to read the herbicide label to determine if the Liriope species in question is on the label.
If weeds have germinated, several postemergent herbicides are labeled for use in liriope or mondograss (Table 2).
As with the preemergent herbicides, most postemergent herbicides are labeled for several species of liriope (i.e., gigantea, muscari and spicata) or mondo grass (i.e., japonicus, jaburan, planiscapus), but some are not! Make sure to read the herbicide label to determine if the liriope or mondo grass species in question is on the label. Some of the postemergent herbicides may require the addition of a surfactant. Check the herbicide label to determine if the herbicide formulation that you are using requires the addition of a surfactant. Using a herbicide without a surfactant, when it requires one, will severely reduce the effectiveness of the herbicide. Spot applications of a systemic broad spectrum herbicide (i.e., Roundup®) may be applied to weeds that are not controlled by these herbicides. Be careful to avoid overspray or drift onto liriope foliage.
Most of the pre and postemergent herbicides listed are labeled for both container and field grown Liriope, but some are not. Refer to the label to determine if the herbicide you are using is approved for field or container grown ornamentals.
Unfortunately, both dwarf mondo grass and liriope can creep into turfgrass and become a weed problem. At present there are no selective herbicides that control dwarf mondo grass or liriope in turfgrass. At present, the only solution is to renovate the infected are by physically removing the dwarf mondo grass or liriope or by treating the infected area with a broad spectrum herbicide (i.e., Roundup®) and reseed or replant.
Information from "Weed Control in Liriope and Mondo Grass" by Mark Czarnota, Ph.D., Ornamental Weed Control Specialist, Department of Horticulture, University of Georgia.
Thursday, June 19, 2008
If a complete renovation of a turf area is to be done, one option is to apply 2 applications of glyphosate herbicide, three weeks apart. Allow sufficient time for any remaining weeds to die after the second application before renovating. Ideally, turf areas should be irrigated to encourage weed growth prior to applying glyphosate as it will not work well on drought stressed weeds. Glyphosate is not totally effective on some perennial weeds such as nimblewill. For troublesome perennial weed patches, Basamid soil fumigant may be an option. Basamid is applied as a granule and is watered in. It performs best if it is tilled in or is tarped with plastic. Research has shown good control of nimblewill, bermudagrass, and creeping bentgrass by fumigation with Basimid. It also controls many soil born pests (diseases and insects) and kills weed seeds and perennial propagules. One advantage to this approach is that seeding can be done 7-10 days after treatment. In contrast, 2 applications of glyphosate will require a minimum of 4 weeks lead time. Another consideration when doing fall renovations is reseeding restrictions for preemergence and postemengence turf herbicides. Read the label for each product that you use and make sure you will have enough time between the last application and desired reseeding date. Examples of reseeding restrictions: Dimension herbicide single application will require a 3 month waiting period before reseeding, 4 months with a split application; Barricade herbicide has a 4 to 7 month waiting period before overseeding depending on the rate used.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
The world of adjuvants is very confusing with much information being proprietary. Often it is recommended by manufacturers or by researchers that specific adjuvants be used with systemic pesticides including herbicides, insecticides, and fungicides, to improve their activity or efficacy. Terms such as surfactant, penetrant, and activator are used to describe what the adjuvant does, and to some degree, the general nature of the additive.
There are two basic actions that must be successful for a systemic pesticide to be effective. First, the chemical must enter into the plant. Second, it must be distributed in the plant to the site of action. Adjuvants are used to enhance entry into the plant.
Adjuvants are added to help the chemical pesticide cover over the leaf surface, move through the cuticle, and in some cases, move into the stomata. Surfactants are a major category of adjuvants. They reduce the surface energy of chemicals applied and water, allowing the chemical to spread over the leaf surface more readily. They have both hydrophilic and hydrophobic components thus working with a wide range of pesticides (whether hydrophilic or hydrophobic). Depending on their formulation, they may work to emulsify, disperse, spread/wet, or solubilize the added pesticide as they interact with the leaf surface.
Surfactants act in a number of ways depending on formulation. They may increase the area of contact of spray droplets with the leaf, increase spray retention, act as a humectant to keep spray droplets moist for a longer time, modify the cuticle by allowing dual solubility in hydrophilic and hydrophobic components as the pesticide moves through the cuticle, produce hydrophilic channels for those pesticides with that characteristic, increase the permeability of the cuticle and cell membrane of the underlying leaf cells, complex with pesticides and lower their surface tension, lower tensions allowing movement between cell walls of the leaf, and enhance entry into stomata.
Organosilicone adjuvants have been shown to enhance the movement of chemicals into the stomates as a major mode of entry for pesticides.
Oil based adjuvants are diverse with two broad catagories: petroleum based and vegetable based. Oils work to reduce vapor loss of a pesticide and for some pesticides, improve entry into the leaf by a number of mechanisms.
Gordon Johnson, Extension Horticultural Agent, UD, Kent County
Wednesday, June 18, 2008
The tick is an arthropod--a relative of insects. The most common ticks found in Delaware are the American dog tick, the brown dog tick and the black-legged tick. The American dog tick, often called the eastern wood tick, rarely invades the home in large numbers. However, the brown dog tick can become a serious household pest in those homes with pets. The deer tick will bite humans as well as domestic animals, but it is generally an outdoor tick.
Life history and habits
Ticks have a four-stage life cycle. The egg hatches into a six-legged larva, or seed tick. After a blood meal, the larva molts (sheds its skin) and becomes an eight-legged nymph. After another blood meal, the nymph molts and becomes an adult. The adult female then attaches to a warm-blooded animal, engorges on blood, mates, leaves the host animal, deposits several thousand eggs and dies. Adults can live a year or more without feeding, but they must feed before mating.
The American dog tick is widely distributed east of the Rocky Mountains and on the Pacific coast. Dogs are the preferred host of the adult tick, but humans and many other animals are frequently attacked. Because larvae and nymphs prefer to feed on mice, rats and rabbits, this tick does not become established as a household pest. The American dog tick is responsible for spreading Rocky Mountain spotted fever.
The brown dog tick differs from the American dog tick primarily in its feeding habits. It feeds almost exclusively on dogs and rarely attacks humans. In all stages it is commonly found on the ears, the back of the neck, and between the toes of dogs. After feeding, the ticks drop off the host and conceal themselves in any available crack or crevice. Because of their strong tendency to climb, they are often found on furniture and behind window frames and moldings.
A smaller tick known as the deer tick has been found on humans and pets. It is associated with areas supporting large rodent rodents as well as deer. Although smaller than the dog tick, its bite is painful because its mouth parts have tiny barbs to anchor it securely. The barbs make removal difficult; they often remain in the skin, causing local infection. This tick is a carrier of a Lyme disease pathogen that causes arthritis-type symptoms and, if not treated, can affect the liver, heart, and lungs.
Identification of a tick found on a person or pet is often difficult. If the tick has been feeding and is engorged, identification is even more difficult. The American dog tick can be distinguished from the brown dog tick by the white mottled shield (scutum) on its back, behind the head.
Brown dog ticks have a shield but it lacks the lighter markings. The deer tick also lacks a color pattern and it is distinctly sbeing no larger than the period at the end of this sentenceavoid ticks, tuck trousers into boots or socks when outside. Search all areas of your body at least daily if you frequent tinfested areas. The deer tick control should eliminate the nymphs since this stage is most likely to transmit Lyme disease. The larval stage is incredibly small--no larger than the period at the end of this sentence (omit – already said this). Sprays with approved insecticides provide some control but don't take such measures unless infestations are confirmed. Always use a repellent and check for ticks on your body.
The best method to remove ticks from a person or pets is with a slow, steady pull. Get the capitulum (mouth parts) out with the rest of the tick. Tweezers work well, especially in removing deer ticks. Place the tweezers as close to the point of attachment as possible and pull steadily away from the skin. An antiseptic will prevent infection and reduce irritation. We can't recommend using fingernail polish, chloroform, ether, gasoline, kerosene, a hot match or needle or a glowing cigarette. These methods can cause more serious injury than the bite itself.
Extracted from the fact sheet "Tick Control" by Dewey M. Caron, Extension Entomologist, UD
With the high temperatures (90 +ºF) that showed up on June 7, 8 and 9th and high humidity, we may start to see plants collapsing with Southern blight.
This fungal blight is caused by Scerotium rolfsii. The fungus can attack most herbaceous perennials. It is active only during hot weather, so plants can grow well in infested soil during most of the growing season, and only become damaged during the hottest part of the summer.
The first symptoms seen are wilting and collapse of individual stems or entire plants. Close inspection of the stem at the soil line reveals white mycelium (strands of fungus growing on the stem and mulch or soil surface), and small (1/8 to 1/6 inch), tan spherical sclerotia that resemble mustard seeds. The sclerotia are white when first formed and gradually, over several days, turn brown. Roots of infected plants are typically unaffected and survive helping plants recover the next season. Cortical decay of the stem at the soil line is common during hot, humid weather. Southernblight is commonly found on many ground covers; including Lysimachia, Ajuga, and Plumbago. It is capable of blighting most herbaceous perennials, vegetables, annuals, herbs and even turf and woody plants.
Management Strategies: The basis for control of Southern blight is to reduce the number of sclerotia surviving in the upper few inches of the soil. During the growing season, remove blighted plants and the mycelium clinging to stems and mulch. Deep cultivation can provide good control by burying the sclerotia. The cornerstone for control of all blight diseases is sanitation both during the growing season and in the fall. Wilted and blighted plants and plant parts should be promptly removed from the garden. Do no compost material killed by southern blight (Sclerotium rolfsii) or white mold (Sclerotinia) because the sclerotia of these fungi may survive composting.
Information from the June 13, 2008 edition of the TPM/IPM Weekly Report for Arborists,
Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.
Tuesday, June 17, 2008
One common problem that I routinely see is over-irrigation in the landscape. This occurs with improper use of manual irrigation systems, automated irrigation systems with design flaws such as improper overlaps, and irrigation systems with maintenance problems such as broken sprinkler heads or missing drip emitters. It also occurs where irrigation scheduling is improperly done so that excess water is applied or is applied incorrectly.
Excessive irrigation can lead to many problems. Frequent, light irrigation can lead to shallow rooting, especially in turf, making plants more susceptible to stress. Excessive watering can increase foliar disease pressure in turf and root and crown rots (Phytophthora, Pythium) in susceptible ornamentals such as Taxus (yew), junipers, azaleas, rhododendrons, Japanese hollies, hemlock, dogwood, Camellia japonica, Pieris, deodar cedar, mountain laurel, heather, high-bush blueberries, white pine, leucothoe, boxwood, and others. Many perennials and annuals such as geraniums and chrysanthemums are also susceptible to these root rots in wet conditions. Over-irrigation also results in nitrogen leaching and runoff. Excess water can lead to increased weed pressure from nutsedge, nimblewill, bent grass, crabgrass and moss and will decrease the longevity of preemergence herbicides. Weed growth on top of mulch is encouraged in landscape beds that stay wet. Drainage ways, low areas, shaded areas, and areas with restrictive soil layers are the most at risk for overwatering.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
Nutsedge has shiny, yellow-green grass-like leaves, a triangular stem (characteristic of sedges as a group) and, if kept un-mowed, will produce a yellow-brown seed head cluster. It spreads by rhizomes and produces tubers that are formed at the end of these rhizomes. One plant can produce up to 700 tubers in a season. Tubers have buds that will send out new shoots following a dormancy period (cold required). Tuber sprouting is promoted by high soil moisture conditions. Viable seeds may also be produced. Yellow nutsedge tolerates light shade and medium mowing heights. It can grow through plastic mulch and may come through landscape fabric. Nutsedge is often introduced into a landscape through tuber infested soils carried with planting material (such as B&B plants).
Control of established patches of yellow nutsedge can be difficult. Hand digging is ineffective unless all tubers are removed from the soil. Tillage and hoeing often promotes nutsedge spread by moving tubers around and cutting tubers that will result in multiple plants being produced. Mulch can suppress nutsedge; however some nutsedge plants can grow through the mulch. Moisture control (keeping areas dry) will limit nutsedge emergence but will not work in irrigated areas. Fortunately, there are several herbicides that are effective on nutsedge. Metolachlor (Pennant Magnum) applied preemergence has provided good control in landscape beds. Halsulfuron (Sedgehammer) applied post emergence has provided excellent control in established woody landscape plantings and in turf. Sulfentrazone (Dismiss and several combination products) gives excellent post emergence yellow nutsedge control in turf and is effective against many other sedges (annual and perennial) such as Kyllinga. There is some concern with using sulfentrazone on tall fescue as injury has been found when applied with fertilizers. Bentazon (Basagran T/O) can be used over the top for nutsedge control in established turf and some ornamentals and as a directed spray in most landscape situations. Two applications are generally needed for best control. Glyphosate (directed, wiper, or spot spray applications) can also control nutsedge; however 2 or more applications are often needed.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
Monday, June 16, 2008
Nimblewill, Muhlenbergia schreberi, is a warm season perennial grass that is a common summer weed in older established turf. It proliferates in moist, shady areas, but also can be found in full sun, especially where there is irrigation. Nimblewill has thin stems that can root at the nodes when touching the ground and forms dense mats. It also spreads by seeds that are produced in late summer. It is similar in appearance to common bermudagrass (wiregrass) in that it has small leaves and is wiry in appearance; however, it can be distinguished by the lack of rhizomes or true stolons and by having a short, membranous ligule (bermudagrass has a hair-like ligule).
Control of nimblewill in landscape beds is accomplished by post-emergence applications of grass herbicides: sethoxidim (Vantage), fluazifop-P-butyl (Ornamec, Fusilade II), and clethodim (Envoy plus). In cool season turf there are no good selective herbicides currently available. Hand digging or use of non-selective herbicides such as glyphosate followed by reseeding or sodding is the recommended control. A new herbicide, mesotrione (Tenacity), is very effective on nimblewill in cool season turf but is only labeled for golf courses and sod farms currently. It will be the standard for control in other turf situations if and when available in the future.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County.
Some plant pests controlled by horticultural oils.
Dormant Season Applications
Aphids that curl leaves in spring
Caterpillars that winter as eggs on the plant (leafrollers, tent caterpillars)
Mites that winter on the plant (e.g., conifer-infesting species)
Scale Insects (e.g., pine needle scale, striped pine scale, Kermes scale, cottony maple scale)
Insects and Mites
-Some aphid-transmitted viruses
The following precautions are recommended whenever using an oil on a woody plant:
-Avoid using oils on plants that tend to be oil-sensitive. Avoid drift onto sensitive plants.
-Do not apply when temperatures are excessively high (above 100 degrees F) or low (below freezing). High temperature limitations are primarily related to the drought-stress status of the plant. Plants under stress may be damaged. Those not stressed are much less likely to be damaged by an oil application. Dry conditions without plant stress generally reduce risk of injury by oil, because evaporation is more rapid.
-Do not apply oils during freezing weather. This can cause the emulsion to break down and produce uneven coverage.
-Do not apply oils if plant tissues are wet or rain is likely. These conditions inhibit oil evaporation. High humidity (above 90 percent) also may contribute to injury risk, while low humidity generally reduces it.
-Do not spray when shoots are growing.
-Avoid treating plants during the fall until after winter hardening has occurred. Fall treatments have sometimes caused increased susceptibility to winter injury.
-Do not apply oils in combination with sulfur or sulfur-containing pesticides such as Captan or Karathane. They can react with oils to form phytotoxic compounds. Because elemental sulfur can persist for long periods, label directions on most oils prohibit their use within 30 days of a sulfur application.
Plants that tend to be sensitive to oils.
Junipers and cedars
Maples (particularly Japanese and red maple)
Spruce (particularly dwarf Alberta spruce)
The neem oil insecticides (Trilogy®) have been most widely used on greenhouse-grown ornamentals. They have shown good plant safety, but there are some precautions for use on impatiens, fuschia, hibiscus, some roses, ornamental olive and some carnation varieties.
Information from "Insect Control: Horticultural Oils" by W.S. Cranshaw, Colorado State University Extension entomologist and professor, bioagricultural sciences and pest management; and B. Baxendale, Teikyo Loretto Heights University professor, botany, Denver from Colorado State University
Sunday, June 15, 2008
Essentially all commercially available horticultural oils (e.g., Sunspray, Scalecide, Volck oil) are refined petroleum products also known as mineral oils. Impurities in the oil that are associated with plant injury, such as aromatic compounds and compounds containing sulfur, nitrogen or oxygen, are removed. Filtration, distillation and dewaxing complete the production of the finished base oil. Final formulations of horticultural oils are normally combined with an emulsifying agent that allows the oil to mix with water. This mixture usually is used at about a 2 percent dilution.
Vegetable oils also can be used as insecticides, although the type of oil can greatly affect its activity. Cottonseed oil is generally considered the most insecticidal of the vegetable oils. Soybean oil, the most commonly available vegetable oil used in cooking, has often provided fair to good control of some insects and mites.
Extracts from seeds of the neem tree (Azadirachta indica) have recently attracted attention as a source of pest management products. Several neem-derived insecticides have been developed. A number of compounds found in neem seeds, notably azadirachtin, have proven useful as insecticides. However, the oil fraction of neem seed extracts, which is mostly free of azadirachtin and related terpenoid compounds, also has demonstrated effects as a fungicide and insecticide. At least one product currently on the market, TrilogyR, consists of a largely azadirachtin-free oil fraction of neem seed extracts. It is formulated with an emulsifier and mixed with water at a concentration similar to horticultural oils (0.5 to 2.0 percent). Many over-the-counter products sold in nurseries that mention neem contain the oils of neem seed extracts.
Historically, the primary reason oils were developed was because of their effectiveness on otherwise hard-to-control pest problems on fruit trees. They were used as a dormant-season application (before bud swelling and bud break) to kill mites and insects, such as scales and aphids, that spent the winter on the plant. Dormant oil applications also control certain overwintered shade tree pests.
Recently, improvements in refining have produced oils with increased safety to plants and thus expanded their potential uses. Summer or foliar treatments are now possible for a variety of pests during the growing season. Oils also can be mixed with other insecticides, providing a broader spectrum and greater persistence of control. Spider mites, whiteflies and young stages of scales are common pests that can be controlled by oils during the growing season.
Oils are sometimes applied to prevent transmission of viruses. Many viruses spread by aphids (nonpersistent viruses), as well as some that are mechanically transmitted by people, can be inhibited by oil applications. Oils used to inhibit virus transmission are sometimes called "stylet oils," a reference to the piercing and sucking mouthparts (stylets) of aphids that transmit these viruses.
Oils also are useful against powdery mildew. Diluted horticultural oils, often mixed with a small amount of baking soda, can be an effective control for this common plant disease. The neem oil products have been effective against several types of powdery mildew and rust.
Information from "Insect Control: Horticultural Oils" by W.S. Cranshaw and B. Baxendale, Colorado State University.
Conditions favoring moss include acid soils, poor drainage and excessive wetness, shade (moderate to heavy), low mower cutting height or turf “scalping” and compaction. Mosses are primitive plants with over 13,000 species. Some mosses require constant moisture, others are well adapted to drying out and then regrowing when moisture is available. Carpet type mosses that survive dessication are the most troublesome for control. An example is Silvery Thread Moss (Bryum argenteum).
Moss control starts with correcting the underlying problems that restrict turf growth (improve drainage, remove shade, lime to raise pH, raise mower height). Chemical controls will suppress moss but will not totally eradicate it and include Quicksilver (carfentrazone) herbicide, Junction fungicide (copper hydroxide plus mancozeb – for golf course use only), and spring applications of Daconil Ultrex fungicide (chlorothalonil). Ferrous sulfate can suppress moss; nitrogen fertilization with ammonium sulfate has provided some moss control; and hydrated lime can suppress moss (some phytotoxicity). Soaps and salts can also be effective. Research has shown that Dawn Ultra dishwashing soap (10 ounces of Dawn Ultra in 2.5 gallons of water) is an effective spot application on moss. Baking soda has also worked as a spot application (6 ounces / gallon of water). Another option is TerraCyte (sodium carbonate peroxyhydrate), a granular product that is applied in the spring or fall. Finally, fatty acid based products (many brands) have provided some control.
In areas where moss grows better than turf, consider converting the area into moss gardens. You can find information about moss gardens at http://www.ext.vt.edu/pubs/turf/430-536/430-536.html.
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
Saturday, June 14, 2008
With the recent rainfall and warm weather, crabgrass (smooth crabgrass, Digitaria ischaemum; large crabgrass, Digitaria sanguinalis) growth can be rapid in turf and landscape beds where preemergence grass herbicides were not applied or where residual herbicide barriers are starting to break down. Ideally, postemergence herbicides should be applied when crabgrass seedlings are still small. In cool season turfgrass, if crabgrass seedlings have not started to tiller, dithiopyr (Dimension) can be used and will provide additional preemergence activity for late germinating crabgrass. Fenoxaprop-ethyl (Acclaim extra) is one option for postemergence crabgrass control in cool season turf. Another option in turf is quinclorac (Drive) which has good safety on new spring seeded stands. In landscape beds several postemergence herbicides provide crabgrass control and can be used over the top of most ornamentals (other than ornamental grasses). This includes sethoxidim (Vantage), fluazifop-P-butyl (Ornamec, Fusilade II), and clethodim (Envoy plus).
Gordon Johnson, Extension Horticulture Agent, UD, Kent County
Phytotoxicity is general term used to indicate spray injury to plants. The signs (chlorosis, burning, tissue distortion, or plant death) may appear from within a few days of application to several weeks later. This article only considers phytotoxicity due to insecticide applications but injury can result from application of other pesticides, nutrients, or other substances. Some plant species or varieties are sensitive to particular chemicals, in other cases, injury occurs only under certain environmental conditions.
Here is an overview of phytotoxicity base on major contributing factors.
1) Some species or cultivars are highly sensitive to particular active ingredients, or inert ingredients in some formulations.
2) Applying more than the labeled rate at one time or treating at very close intervals.
3) Tank mixing several pesticides. Synergism or antagonism from combinations in spray tanks can result in injury. Some formulations contain ingredients that interact with ingredients in other products.
4) Pesticide applied at a susceptible growth stage - around bud break or during flower development.
5) Stressful environmental conditions - especially during periods of excessively high temperatures, while plants are under drought stress, or when sensitive foliage is wet longer than normal.
Be aware of susceptible species or cultivars for the products you use.
Use separate tanks / sprayers for herbicides, insecticides, fungicides as practical.
Read the label before application - especially check for instructions on tank mixes and potential for plant injury. Follow application rates and retreatment intervals.
Avoid adding adjuvants (spreaders, stickers, wetting agents, etc.) unless their use is specifically stated on the label.
Treat small numbers of plants with tank mixes and watch for symptoms before treating large areas or numbers of plants.
Don't treat under adverse environmental conditions (temperature, humidity) or when plants are under stress.
Select formulations carefully. Solvents in emulsifiable concentrates (EC) formulations tend to have a much higher potential for damaging plant tissue than wettable powder (WP) or flowable (F) formulations.
Be aware of pest damage or abiotic conditions that can cause injury that resembles phytotoxicity. Patterns and timing or appearance of symptoms may be helpful in identifying potential causes of injury.
In some cases, pH of water used in the spray tank may affect pesticide performance.
Example label statements for selected insecticides
Horticultural oil - Do not apply during periods of drought or when plants exhibit moisture stress. Injury may occur on the most oil tolerant plants if relative humidity is low and wind and temperature are high. Summer spray oils should not be applied when the temperature is 90F or above or when the humidity is high. Blue spruce may lose its blue color for a few years after an oil spray.
Insecticidal Soap - Do not spray when plants are under stress. Avoid spraying during full sun. Spray early in the morning or evening, or when overcast. Soap spray may cause marking of some varieties.
Malathion - Injury may occur on certain ferns including Boston, Maidenhair, and Pteris, as well as some species of Crassula. Before using Malathion EC alone or with any other material, make a test application on a few plants and observe for 7 to 10 days prior to treating large areas to reduce the possibility of plant injury.
Orthene 75% Turf Tree, and Ornamental Spray (acephate) - Do not apply to Huckleberry, Balm of Gilead, cottonwood, Lombardy poplar, and Viburnum suspensum.
Phytotoxicity has occurred on the following Crabapple varieties: Hopa, Ichonoski, Malus floribunda, Pink Perfection, Red Wine and Snow Cloud. Phytotoxicity has occurred on Bletchum gibbum, Cissus antarctica, Ficus triangularis, Fittonia verschaffeltii, Maranta leuconeura kerchoveana, Pachystachya lutea,, Plectranthus australis, Polypodium aureus, Polystichum, Pteris ensiformis, Tolmiea menziesii. A spray on Poinsettia after bract formation may result in phytotoxicity on certain varieties. Phytotoxicity has occurred on the following Chrysanthemum varieties: Albatross, Bonnie Jean, Dixie, Garland, Gem, Iceberg, Pride, Showoff, Statesman, Tally Ho, Westward Ho, and Wild Honey. Do not apply to Chrysanthemums and Roses with open flowers. Tank mixing or use of this product with any other product which is not specifically and expressly authorized by the label shall be the exclusive risk of the user, applicator, applicator/advisor.
Sevin (carbaryl) Application to wet foliage or during periods of high humidity may cause injury to tender foliage. Do not use on Boston ivy, Virginia creeper, and maidenhair fern as injury may result. Carbaryl may also injure Virginia and sand pines. The use of adjuvants may increase the potential for crop injury to sensitive crops. General statement - It is impossible to eliminate all risks associated with the use of as product, Crop injury, ineffectiveness, or other unintended consequences may result because of such factors as weather conditions, presence of other materials or the manner of user application, all of which are beyond the control of the manufacturer. All such risks shall be assumed by the user or buyer.
Reprinted from "INSECTICIDE PHYTOTOXICITY" By Lee Townsend in the June 9, 2008 edition of the Kentucky Pest News.
Friday, June 13, 2008
Scientific Name/Common Name
Plants listed in boldface are most commonly affected by powdery mildew.
Begonia sp. Begonia
Cotinus coggygria Smoke-tree
Cotoneaster sp. Cotoneaster
Crataegus sp. Hawthorne
Eucalyptus sp. Eucalyptus
Euonymus sp. Euonymus
Hydrangea sp. Hydrangea snowball
Lagerstroemia indica Crape myrtle
Leucothoe sp. Leucothoe
Ligustrum vulgare Privet
Lonicera sp. Honeysuckle
Magnolia sp. Magnolia
Malus sp. Apple, Crabapple
Phlox paniculata Phlox
Photinia serrulata Chinese photinia
Platanus sp. Sycamore
Prunus sp. Peach, Plum, Apricot
Pyracantha sp. Pyracantha
Pyrus sp. Pear
Quercus sp. Oak
Rhododendron sp. Rhododendron, Azalea
Rosa sp. Rose
Salix sp. Willow
Spiraea sp. Spiraea
Syringa vulgaris Lilac
Vaccinium sp. Blueberry
Viburnum sp. Viburnum, Snowball
Wisteria sp. Wisteria
Zinnia elegans Zinnia
Information from North Carolina State University Plant Pathology Extension
The fungi which cause diseases known as powdery mildew attack a wide variety of ornamental plants grown in Delaware.
The damage due to infection by the fungi causing powdery mildew can be slight to severe. The disease generally occurs in Delaware during late spring, late summer and fall in cool to warm weather with high relative humidity and in shady areas.
A powdery, fluffy white to light gray-colored fungus growth on succulent stems, leaves, buds and flowers is the characteristic symptom of powdery mildew. Young plants and actively growing shoots are more severely damaged than older plants, leaves or branches. Infected leaves may be dwarfed, curled or deformed. Powdery mildew can destroy the blossoms on crape myrtle. Small dead flecks in the leaves and defoliation may occur on some varieties of azalea and rhododendron that are infected with powdery mildew without the obvious development of white fungus growth.
The white mildew on the plant surface is actually composed of the threads (mycelium) and asexually produced spores (conidia) of the powdery mildew fungus. These spores are wind-blown to other parts of the same plant or other plants of the same species. Powdery mildew fungi are quite host-specific, so for example the mildew on zinnia will not spread to dogwood or sycamore, and vice-versa. Also, they are obligate parasites, meaning that they can only grow on living plant tissue.
Some powdery mildew fungi survive the winter as colonies of mycelium, but many switch over to sexual reproduction in the fall, producing minute brown to black specks amid the old mycelium on the dying leaf or other plant part. These survive the winter and in the spring release another type of spore to start the cycle over.
Some highly susceptible plants, such as Chinese photinia or euonymus should be replaced with a similar plant that is not susceptible to powdery mildew. On many trees, the disease causes little or no damage, therefore, control is not necessary. Plants in the landscape which may require fungicide applications to prevent powdery mildew damage include crape myrtle, phlox, rose and zinnia.
If damage from powdery mildew is severe and a susceptible plant(s) must be grown in the landscape, prune out severely diseased portions and use one of the following fungicides according to label instructions:
Propiconazole (Banner Maxx) is registered for control of powdery mildew and numerous other diseases on ornamentals.
Myclobutanil (Systhane, Eagle, and Immunox) is registered for control of powdery mildew and numerous other diseases on ornamentals.
Sulfur as a spray or dust as needed. Sulfur may cause some plant injury if applied when air temperature exceeds 90 F.
Triforine (Funginex) is labeled for use on roses and several other ornamentals. Follow manufacturer's instructions on the label. This product is only available in small packages.
Triadimefon (Bayleton and Strike) is now registered for use on a number of ornamentals.
Fenarimol (Rubigan) is a locally systemic fungicide for the prevention or therapeutic control of powdery mildew of field or landscape grown ornamentals.
In some situations copper fungicides will provide control of powdery mildew.
Note: The powdery mildew fungi can become resistant to any one of the fungicides listed above except sulfur.
Information modified from "Powdery Mildew of Ornamentals and Shade Trees" Ornamental Disease Information Note 4, R.K. Jones, Extension Plant Pathologist and D.M. Benson, Plant Pathologist, North Carolina State University Plant Pathology Extension
Thursday, June 12, 2008
The list of host plants for the Two Spotted Spider Mite, a warm season mite, is considerable. A partial list includes many perennials, winged euonymus, and occasionally juniper and dwarf Alberta spruce. Typically conifers are not the preferred hosts of two-spotted spider mite species. These mites can have an entire generation occur in less than 7-8 days if temperatures exceed 85° F. It is possible for 15 generations of two-spotted spider mites to occur during the summer. Typical symptoms include stippling damage and webbing. Affected foliage yellows, then turns brown and dies if mites are not controlled. Damage does not recover, so early detection and timely control is the best management technique. Monitor with a beating tray (or white clipboard) by rapping foliage on the board and looking for the tiny mites that drop off. A hand lens can be used to note what life-stage is present (on the underside of foliage), but this is slower than the use of the beating tray. Very fast predatory mites may be seen, with light colored bodies and long legs. If predators are noted, keep monitoring to be sure they are reducing the spider mite population, and that the mites don’t overwhelm the predators.
Control with horticultural oil (check the label for weather conditions and make sure the plant is not under drought stress) in order to kill eggs and active forms, as long as mites are contacted (on the underside of foliage). Hexythiazox (Hexygon) is a miticide that kills immature mites and eggs and prevents adults from laying eggs. Abamectin (Avid) provides a quick kill and a long residual (may need 2 applications since they only control active mites. Florimite is a miticide that can also provide excellent results. The list of effective miticides is extensive. Note that imidacloprid (Merit) is not a miticide.
Information from the June 28, 2007 edition of the Plant and Pest Advisory, Landscape, Nursery and Turf Edition, Rutgers University.