Tuesday, June 30, 2009
You or your clients may notice honeydew on cars and sidewalks. This is a sign of aphid infestations in nearby trees or shrubs. There are a number of aphid species that feed in landscape trees and go largely unnoticed until honeydew rains down on surfaces where it is not wanted. Many tree species and large shrubs can be attacked by aphids. Fortunately, aphids are often “cleaned up” by ladybugs and other natural enemies and do not cause permanent harm to the trees. However, on nursery stock, landscape specimen plants, or trees that shade a client’s fancy car, control may be needed. Luckily there are a number of products such as imidacloprid, Tristar, Safari and others that can provide long term aphid suppression and can often be applied in foliar or drench applications.
Adapted from an article in the North Carolina Pest News http://ipm.ncsu.edu/current_ipm/09PestNews/09News7/pestnews.pdf
Soon they will be flying again, the adults of those pesky white grubs, like oriental beetle, Japanese beetle, masked chafers, Asiatic garden beetle, European chafer, and green June beetle. Adult oriental beetles typically peak in abundance from late-June into early July, followed by Japanese beetles about mid-July. Peak adult activity means peak egg-laying which is followed 2-3 weeks later by peak hatching off the eggs.
The young first stage larvae are the stage that is the most susceptible to insecticides, and numbers of this stage peak from mid-July to early August. If an applicator chooses to preventively treat turf for white grubs, the ideal time to do an application would be somewhat earlier than the time of peak first larval stage density to allow the insecticidal active ingredient to reach peak concentration in the target zone, i.e., the thatch and top 1-2 inches of the soil. How much earlier depends on how fast the active ingredient will move through the thatch. Generally, the more water soluble an active ingredient is, the faster it will move downwards into the soil with rain and irrigation water.
However, the application window of most of the newer white grub insecticides is rather wide and many of them can be applied from May into August with little differences in control rates. Reasons for these wide windows are that (1) the active ingredient has a long half-life in the soil allowing earlier applications, (2) the second larval stage of the white grubs is generally still very susceptible to the active ingredient allowing later applications, and/or (3) the recommended application rates are high enough to compensate for 1-3 months of slow active ingredient breakdown in the soil or the lower susceptibility of the larger white grubs.
Imidacloprid (Merit) and thiamethoxam (Meridian) seem to be very effective when applied from May through August, clothianidin (Arena) even from May into September, halofenozide (Mach2) from June through August, and chlorantraniliprole (Acelepryn) from April at least into mid-August.
An interesting new finding is that chlorantraniliprole (Acelepryn) actually tends to be more effective when applied earlier. Due to its very low water solubility (> 5 ppm) chlorantraniliprole takes around 50 days to reach peak concentration in the thatch and 100 days to reach peak concentration in the soil. However, chlorantraniliprole clearly is effective enough to compensate for this slow movement. Averaged over dozens of research trials for each application timing, chlorantraniliprole at 0.1 lb active ingredient per acre applied in April, May, June, July, and August has provided 96%, 94%, 91%, 88%, and 79% control, respectively, of all the major white grub species. However, even the 79% control in August is at least as good as what one can expect with an application of trichlorfon (Dylox) and certainly good enough to suppress white grub damage.
As always, keep in mind that repeated application of the same insecticide class year after year could lead to insecticide resistance and/or enhanced microbial degradation of the compound. Enhanced microbial degradation would be particularly problematic if the compound is applied several weeks to months before the presence of the target (i.e., before July). Therefore regularly rotate insecticides from different insecticide classes. Earlier applications are also more likely to interfere with naturally occurring predators and parasites of white grubs and other turfgrass insect pests. Applications before July or even June should therefore be reserved for cases where there is some additional benefit such as suppression of other insect pests with damage potential.
Reprinted from "Timing of White Grub Treatments in Turfgrass" by Albrecht M. Koppenhöfer, Ph.D., Specialist in Turfgrass Entomology in the June 11, 2009 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2009/ln061109.pdf
Monday, June 29, 2009
Over the years, I have observed plant growth problems in the landscape associated with low pH. In most of these cases, the soil in the poor growth area was quite acidic, pH in the 5.2 or lower. Available soil nutrient levels were often adequate. However, the plant tissue analysis in these samples showed low phosphorus and magnesium levels and in some cases elevated levels of iron and aluminum. Without soil pH information, one may have concluded that the plant growth problem was due to inadequate available phosphorus or magnesium in the soil.
The remedy is applied needed lime to those individual spots, not applying phosphorus or magnesium. When the soil pH is below 5.2, availability of aluminum, iron and manganese increases significantly. This results in increased uptake of these three elements. Aluminum and manganese begin to accumulate to the point of becoming slightly toxic and reducing root growth. Reduced root growth results in greatly reduced uptake of phosphorus, which is relatively immobile in the soil. Uptake of other nutrients will also be reduced, resulting in poor growth. Magnesium availability decreases as the soil pH decreases, especially below 5.2, resulting in low levels in the plant. Also, under acidic soil conditions microbial activity is reduced, resulting in reduced mineralization of nitrogen and sulfur from soil organic matter and organic soil ammendment.
It is not unusual to see acid spots in landscapes even with overall soil pHs in the 5.8 to 6.5 range. These spots can vary greatly in size. Theses spots are usually found in newly developed properties where subsoil was exposed or inadequate topsoil replaced, in the sandiest areas, or in turf were excessive N fertilizer is being used. Subsoil is naturally acid in DE and exposed subsoil or inadequate replacement of topsoil will result in acid spots. Excessive applications of N fertilizers results in areas becoming acidic more quickly. In very sandy spots, excess leaching of basic cations results pH dropping rapidly. When diagnosing plant growth problems, be sure to check soil pH first and look at the plant roots.
Adapted from "Soil pH, the source of plant growth problems" from Darryl Warncke, Crop and Soil Sciences, Michigan State University on the MSU Field Crop Advisory Alert web site.
An excellent new reference for plant enthusiasts was just published by APS Press, “Diseases of Herbaceous Perennials”. It will be the 'bible' of perennial disease identification for some time. It is full of excellent full color photos of your favorite diseases comparable to other coffee table books. Horticultural information and pictures of healthy plants are provided by Dr. Alan Armitage, noted perennial plantsman. Ordering information can be found at
http://www.shopapspress.org/hepepl.htm. Price is $79.00.
Sunday, June 28, 2009
Disease management. Powdery mildew can be confronted by using cultural practices, planting resistant dogwoods, and by using fungicides.
Avoid cultural practices that stimulate succulent growth and encourage powdery mildew. These include applying nitrogen fertilizer, pruning heavily, and irrigating excessively.
Use good cultural practices such as mulching over the root system, pruning out dead branches, and providing good air movement and light penetration by judicious pruning of nearby vegetation.
Plant dogwood species and cultivars resistant to powdery mildew.
Susceptible: All Cornus florida, seedling wild types (but individuals vary in susceptibility) and most C. florida cultivars.
Intermediate susceptibility: C. florida ‘Cherokee Brave’ and cultivars of the C. florida x C. kousa hybrids.
Resistant: Four powdery mildew resistant C. florida cultivars have been developed by the Tennessee Agricultural Experiment Station and are available in the nursery trade. They include ‘Jean’s Appalachian Snow’, ‘Karen’s Appalachian Blush’, ‘Kay’s Appalachian Mist’, and ‘Appalachian Joy’. Also resistant: Cultivars of C. kousa, oriental dogwood.
Immune: Cornelian cherry dogwood, C. mas.
If fungicides are to be used, determine which trees in the landscape are most susceptible so that applications are not made unnecessarily. Those trees most at risk for powdery mildew disease then can be considered for preventive fungicide applications. Most fungicides are capable of stopping the progress of powdery mildew infections fairly quickly, but none will restore already discolored or damaged leaf tissues. Good control can be obtained with as few as four fungicide applications made three weeks apart. Begin applications by early June. Delayed application can still help protect some leaves.
Effective fungicides include:
myclobutanil (Eagle, Immunox, Procoz Hoist)
propiconazol (Banner Maxx, Procon-Z, Procoz Fathom, Propensity)
thiophanate-methyl (Cleary’s 3336)
triadimefon (Bayleton, Strike)
Powdery mildew fungicides requiring more frequent applications to be effective include:
neem oil (Triact)
potassium bicarbonate (Bonide Remedy, FirstStep, Kaligreen, Milstop)
paraffinic oil (Sunspray UF Oil)
When using fungicides for powdery mildew management, be sure that dogwoods are listed on the label and carefully follow all label directions.
Information from an article by John Hartman in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090623.html
Downy mildews that are rather uncommon in the area have been favored by the continued rainy, cool weather. Downy mildew of rose occurs worldwide but is rare here. Infected leaves develop purplish red to dark brown irregular spots and leaflets may turn yellow with ½-inch islands of normal green tissue interspersed. Leaf loss can be severe and symptoms may resemble pesticide toxicity burns. Sanitation is important, since the fungus overwinters in infected leaves. Rake and dispose of fallen leaves, stems and flowers. The other downy mildews have been diagnosed on sunflower and black-eyed Susan, both infected by Plasmopara halstedii. Usually this downy mildew appears in the fall with cool and wet conditions, but not this year. It causes yellow to dark blotchy areas on the upper leaf surfaces and grayish white fuzzy growth on leaf undersides. It can infect most species of Rudbeckia especially 'Goldstrum'. Preventative fungicides can help suppress or control downy mildew. A return to normal weather this week will slow disease development.
Downy mildew on rose. Photo from the Oregon State University Online Guide to Plant Disease Control.
Information from Bob Mulrooney, Extension Plant Pathologist, UD
Saturday, June 27, 2009
Flowering Cabbage and Kale
The flowering kales were very poplar back in the 1990s but have somewhat died-down in popularity since then. Keep in mind this is an 11 week crop so for late fall don’t start your plants until mid- July. The color really comes on when it starts getting cold at night. The seed for most commercial cultivars was developed by Sakata Seed America or Takii America. The seed is available through many different wholesale seed companies.
The shape of the leaf determines whether it is called flowering cabbage and or flowering kale. Cultivars with smooth leaf margins constitute the flowering cabbage group while those with divided or "fringed" leaf margins are considered flowering kale. Within the kale group there are two types: the most common are the "fringed leaved cultivars" which have finely ruffled leaf margins and a smaller number which are called "feather leaved cultivars" have leaves that are finely serrated and deeply notched. A grower should select depending on growth habit and coloration that your customers want.
In each series there is normally a white, pink, and red cultivar.
Flowering cabbage cultivars: Tokyo series, Osaka series, Pigeon (red, pink and white) and Color-up series
Fringe-leaved cultivars – Sparrow series, Chidori series and Kamone series (reds and whites), and Naygoya series
Feather-leaved cultivars – ‘Coral Queen’, ‘Coral Prince’, ‘Red Peacock’, and ‘White Peacock’
Culture: The tough part is that growing ornamental cabbage and kale in summer in Maryland can be challenging if the temperatures are high. Cabbage and kale grow best in cool weather (55º to 60º F) nights. Since outdoor temperatures frequently exceed this range during the summer, select a site which has good air circulation and is "relatively" cool.
With high temperatures in the summer there will be excessive stem elongation due to high temperatures. To prevent stem elongation make a 1500 to 3000 ppm B-Nine application when the plants have developed true leaves and before stem elongation occurs. Several applications (it might be as often as once a week) at the same rate may be made during July and August as needed. Do not apply B-Nine if the crop is going to be marketed as an edible crop. Plant
Nutrition: Maintain the substrate pH levels between 5.8 and 6.5. Many growers have used controlled release fertilizers with cabbage and kale with good success. Begin fertilizing at the rate of 50 to 100 pm N and K after seedlings emerge. Once transplanted, fertilize at the rate of 150 to 250 ppm N and K with periodic applications of a complete fertilizer such as 20-10-20. Make sure you keep the fertility and mist levels correct or the plants suffer. Lack of nitrogen will result in the plants turning yellow and losing lower leaves. Maintain fertilization until night temperatures drop and coloration begins which is October in Maryland. In October reduce fertilization to 50 ppm N and K. Excess nitrogent during this period will prevent good coloration.
Reprinted from the June 26, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension, Central Maryland Research and Education Center.
Japanese beetles are emerging across the state. Adult activity typically occurs between 1094-2410 GDD (base 50). They are highly mobile and feed on over 300 different types of broad-leaved plants. Last year JB adult populations declined in some locations with drier weather in July. Leaves are skeletonized by beetles feeding in between leaf veins. Preferred plants include roses, cannas, flowering crabapple, lindens, Norway and Japanese maples, and elms.
Many natural enemies attack JB life stages such as: assassin bugs, parasitoids, ants, ground beetles, rove beetles, birds, skunks, and raccoons. Cultural control includes hand removal, removing beetle-damaged leaves, or shaking beetles into buckets of soapy water.
Control adults with insecticides including Orthene, Sevin, or one of the pyrethroids (e.g., cyfluthrin, deltamethrin, etc.). Apply insecticides every 1-2 weeks when adult activity is high. Neem based products typically deter feeding for 3-4 days, although some report longer activity. Last year, we reported wettable powder formulations of some pyrethroids (pyrethrins) may be more repellent than EC formulations. Thorough coverage is required. Insecticidal soaps, plant extracts, and companion plantings are generally ineffective. Since adult beetles are mobile, control of white grubs or adult JB does not ensure control of the other life stages. Treat for white grubs using preventive products such as Merit or Mach 2 in mid-June to mid-July. Acelepryn is a new product with a different mode of action than Merit and may be applied as early as May for effective grub control.
Information from Brian Kunkel, Ornamental IPM Specialist, UD.
Friday, June 26, 2009
The twospotted spider mite, Tetranychus urticae, is an important pest of ornamental and food crops. They feed on over 100 species of plants by sucking the fluid out of cells in leaves and needles. This “stippling” damage can rapidly cause entire plants to take on a bronzed appearance. It is important to scout for twospotted spider mites now because they reproduce most rapidly in hot dry weather. Under these conditions they can mature from egg to reproducing adult in 5 days! Look on the underside of leaves on susceptible hosts or beat foliage on a white piece of paper to scout for spider mites. If you notice mites or their damage a range of control options are available, the best of which are several new miticides that provide long residuals and efficacy against all mite life stages.
CLICK ON TABLE FOR A LARGER VERSION OF MITE CONTROL RECOMMENDATIONS
Information from North Carolina State University:
Japanese Honeysuckle, Lonicera japonica, is in flower across Delaware. Leaves are mostly oval to somewhat lobed, opposite, in pairs. Honeysuckle often remains evergreen through the winter. Flowers are tube shaped, white to pink, turning yellow with age and occur in pairs along the stem at leaf axils. They have a distinctive fragrance. This invasive woody vine is common along wood edges, ditch banks, roadsides, fence lines, low maintenance areas, and right of ways. It was introduced in the early 1900’s from the Far East. It is an aggressive climber and can smother desired shrubs and trees and cover fences or posts.
Control small patches by hand digging. Mowing repeatedly is partially effective on large areas. Mow twice, one in July, again in September and repeat each year. In areas where it is climbing vegetation,cut at the base and remove vines. Apply a herbicide to cut stems. Use a 50% glyphosate herbicide or 25% triclopyr herbicide solution (based on formulated products such as Roundup or Garlon). Foliar applications of a 1-5 to 2.5 % glyphosate or a 2% triclopyr herbicide (formulated product) sprayed to runoff can provide control but repeated applications may be needed. Treat in the fall, when non-target plants are going dormant. Avoid contact with desired plants that are still in leaf.
Gordon Johnson, Extension Horticulture Agent, UD
Thursday, June 25, 2009
Prevention - Select nursery sites with well-drained soils. Phytophthora root rot in nurseries can be greatly reduced by improving soil drainage and limiting irrigation. Do not transplant seedlings from infested nurseries into disease-free ones. Avoid using diseased trees for mulch because chlamydospores or oospores may survive in this host material for several years. Avoid movement of equipment between infested and noninfested areas. Diseased seedlings should be lifted separately and destroyed by fumigation or burning. Any effort to save healthy looking trees within diseased areas will result in the spread of the fungus to other areas of the nursery and to outplantings. After working in infested areas, clean equipment thoroughly with steam or an equivalent method.
Chemical - Fumigate soil with methyl bromide and chloropicrin mixture to reduce damage. Unfortunately, fumigant penetration in heavy soils is often inadequate. Metalaxyl, a selective systemic fungicide, is registered as a seed-bed soil drench for seedlings of Fraser fir and Douglas-fir. Two annual applications of metalaxyl are effective in controlling Phytophthora root rot.
Phytophthora root rot progressing up the stem of a seedling.
Information from http://www.forestpests.org/nursery/phytophthora.html
On certain evergreens, pine spittlebugs overwinter in the egg stage. When the nymphs hatch from their eggs, they begin to feed. Spittlebugs suck sap out of the plants with their needle-like mouthparts. As the nymphs feed, they excrete spittle that protects them from predaceous mites and insects and keeps them from drying out. There is only one generation per year. In July and August, female pine spittlebugs lay their eggs in dead wood or under the bark of live stems of pines, spruces, firs, hemlock and other conifers. Control is usually not needed. However, heavily infested Leyland cypress, junipers or pines could be treated with Orthene or some other contact insecticide as spittle masses or when the adults are present in early summer. A strong stream of water from a hose could dislodge them enough to make on impact in the home landscape.
Information adapted from the June 6, 2008 edition of the North Carolina Pest News from NC State University.
Wednesday, June 24, 2009
The bagworm, Thyridopteryx ephemeraeformis, is a common defoliator and pest of arborvitae, spruce, juniper, Leyland Cypress and many other species of woody plants in the landscape and in nurseries.
In bagworms the adult female is both wingless and legless, so that dispersal to new locations is totally dependent on the larval, or immature stage. Bagworm eggs spend the winter inside the maternal bag, which is usually attached to the host upon which the mother developed. In spring, the newly-hatched larvae spin strands of silk and drop from the tip of the mother's bag or from the host foliage. The wind breaks the silk at the point of attachment and lifts the insect into the air with the silk trailing, a process referred to as "ballooning".
Bagworms can also disperse to a lesser degree as older larvae by crawling overground. This occurs mainly when the host foliage becomes depleted before the caterpillars have matured.
About 75% of hatched bagworms first formed a tiny bag from silk and covered it with bits of bark. Newly hatched bagworms generally exited from the maternal bag between 9 AM and noon. Most larvae that ballooned without a bag did so in the morning, while those dispersing with a bag did so mainly in the afternoon.
Larvae ballooning from 15 ft height on an 11 mph wind could easily disperse 245 ft downwind without a bag, and 150 ft with a bag. Although dispersing with a bag makes the larva heavier and reduces the distance it can be blown, dispersing with a bag may help the larvae to survive should it fail to land on a suitable host.
50% of the larvae dispersing with bags survived at least 3.5 days off of a host, whereas larvae without bags survived only 1.5 days. The bag seems to provide protection from desiccation and solar radiation, which would be readily absorbed by the dark-colored larva. This may allow time for a larva that is unsuccessful in landing on a host on its first attempt to climb back up to a suitable vantage point so it can balloon again.
Most bagworms hatching from an egg mass disperse from the "parental" host plant regardless of the degree of defoliation. Since progeny from just a few females could completely defoliate a small host, dispersal may be imperative in order to survive. These findings have significance for nurserymen, landscape managers and homeowners who must deal with bagworm problems.
New bagworm infestations originate mainly from ballooning larvae, so failure to control populations upwind from preferred hosts may leave a reservoir of potential dispersants. Since the ballooning period lasts about a month (June in DE) it may be advisable to wait for several weeks after the first larvae are observed exiting from maternal bags before implementing controls. Bagworms are a potential problem each year since most individuals hatching on hosts in wood lots or hedgerows will be ballooning regardless of host condition.
Information from "AERIAL DISPERSAL BEHAVIOR OF THE BAGWORM" by David L. Cox2 and Daniel A. Potter, Department of Entomology, University of Kentucky in the Journal of Arboriculture 16(9): September 1990
Late blight was confirmed this morning on potatoes in Kent County, DE. Hopefully this is not the aggressive genotype that caused the last outbreak, the fact that the stems were not infected at this time and that the infections were not deep in the canopy suggests that the source was airborne sporangia (spores) and this is not the US8 that was so aggressive on potatoes. Samples will be checked to see what genotype it is.
Late blight on potato leaf. Photo by Nancy Gregory, Extension Plant Diagnostician, UD.
Underside of potato leaf with late blight. Photo by Nancy Gregory, Extension Plant Diagnostician, UD.
Late blight appears on potato or tomato leaves as pale green, water-soaked spots, often beginning at leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. In dry weather, infected leaf tissues quickly dry up and the white mold growth disappears. Infected areas on stems appear brown to black and entire vines may be killed in a short time when moist weather persists.
Non-comercial growers and home gardeners should also be on the look for late blight. If found in gardens, it is recommended that the plants be destroyed as there are no fungicide products registered for control in the home garden.
Report from Bob Mulrooney, Extension Plant Pathologist, Plant and Soil Sciences Dept., University of Delaware. Late blight symptom description from the Ohio State University factsheet "Late Blight of Potato and Tomato" HYG-3102-95.
Tuesday, June 23, 2009
Watch for Phytophthora shoot dieback and canker on Rhododendrons in shaded wet areas. Leaf spotting and blighting progresses to a dieback of the branch tip. Often the petiole will be brown or black and a V-shaped wedge of blackened leaf tissue will be evident where the petiole attaches to the leaf. Dead shoots are often seen close to the ground first because the fungus will splash from the soil to the leaves. Prune out any infected shoots, cleaning the shears between cuts with rubbing alcohol, 10% bleach or other disinfestant. Professional landscapers can apply Subdue or Aliette; homeowners should use mancozeb or a copper fungicide. Prune rhododendrons so the lowest branches are not touching the soil.
Rododendron wilt, otherwise known as Phytophthora root rot, is caused by the fungus Phytophthora cinnamomi. This fungus infects rhododendron, azalea, mountain laurel, blueberry, heather, Irish-heath, Leucothoe, spike-heath, wintergreen, Arbutus unedo, bear-berry, and Pieris.
In infected plants the leaves become pale, droop, roll downward parallel to the midrib, and wilt. The leaves eventually die. Death may occur in as few as 14 days in susceptible young plants, or death may not occur for up to a year in older plants or less susceptible varieties. Individual branches may die. These branches usually have a canker at their base if the plant is young. Underground, small roots become infected first and turn brown. The roots die, although the plant may grow more roots if the plant is older and established. The fungus grows into the stem and when the bark is cut away, the region where the bark attaches to the wood is dark brown.Some less susceptible cultivars may not wilt until all the roots have died. The youngest leaves may turn yellow between the veins, near the midrib. These areas eventually turn brown. Large, well-established plants often have few aboveground symptoms.
Some varieties of Rhododendron are resistant, including Caroline, Professor Hugo de Vries, and Red Head. A few others are moderately resistant. Some azaleas are also resistant to this disease, including Formosa, Fakir, Corrine Murrah, and the Indica hybrids. It is important to use resistance whenever acceptable, particularly in sites where P. cinnamomi is known to exist.
Information from Bob Mulrooney, Extension Plant Pathologist, UD and the University of Connecticut IPM Website.
The rains are producing calls about slime molds, stink horns, puff balls, and other mushrooms in mulched beds and turf. All of these fabulous fungi are just a nuisance--not pathogenic to plants in these beds or turf. Just rake them out or spray the slime molds with a hose to remove them. They are utilizing the organic matter present as a food source and are doing what comes naturally to them, decomposing and recycling organic matter.
Slime Mold in Turf
Monday, June 22, 2009
Dogwood borers appeared in Longwood pheromone traps this week. Four-lined plant bug damage to shrubs perennials has been noted in one or two spots. It appears as small circular holes that look like buckshot on new, but fully expanded leaves. Damage occurred several weeks ago so the control window is gone. Fletcher scale and white prunicola scale crawlers are emerging.. Control crawlers with a foliar absorbed insecticide. Redheaded flea beetle adults are out and feeding. Bagworms have hatched and are feeding now.
Information from the Ornamentals Hotline from the University of Delaware Cooperative Extension.
Four-line Plant Bug Adult. Photo from Plant & Pest Digital Library, Purdue University.
White Prunicola Scale Crawlers. Photo from the Branching Out newsletter from Cornell Cooperative Extension.
Fletcher Scale Adults and Crawlers. Photo from the Kansas Department of Agriculture.
Dogwood borer adult female. Photo by James Solomon, USDA Forest Service, Bugwood.org
Hatching bagworm caterpillars from bag of female. Photo from the Texas A&M Landscape IPM website.
Sunday, June 21, 2009
That time of the year is fast approaching. The beetles will be flying and checking out your turf for nice egg-laying sites. Oriental beetles will come first followed by the more in-your-face Japanese beetles within the next three weeks. This is the time to think about white grub management. The question is whether to apply a preventive application that is more expensive and often not necessary, or to take your chances and apply a curative application later if monitoring suggests damaging grub densities.
July would be the best time to bring out any preventive application. However, such preventive applications should be restricted to areas with very low damage threshold and tolerance, areas with a history of white grub infestations, and areas with high beetle activity (egg-laying) in June-July. Remember that the dominant white grub species may vary in Delaware and may include the oriental beetle, Japanese beetle and Asiatic garden beetle. Other species like northern masked chafer and green June beetle can also cause damage in some locations. Keep in mind that species attacking turf can vary to some extent from year to year and can vary dramatically from site to site.
Information adapted from "To Treat or not to Treat: Update on Preventive White Grub Treatments" by Albrecht M. Koppenhöfer, Ph.D., Specialist in Turfgrass Entomology, Rutgers University in the June 26, 2008 edition of the Plant and Pest Advisory, Landscape, Nursery & Turf Edition, Rutgers Cooperative Extension.
Saturday, June 20, 2009
CEDAR-QUINCE RUST is present on Washington hawthorn, Crataegus phaenopyrum. Symptoms include old swollen twigs from last year and swollen deformed fruit (very evident now). Fungicide control is rarely needed. The same fungus infects serviceberry-- seen this past week. The alternate host is juniper, especially ground cover species. Cedar-quince rust rarely causes any serious damage to the host, just loss of fruit display and dead shoots, which can detract from overall aesthetics.
POWDERY MILDEW is present in many perennials. Look for infection on peony, Monarda (Bee-balm), garden phlox and other susceptible plants. It is controlled well with a number of fungicides (apply at the first sign of disease) as well as hort oil, neem oil, and potassium bicarbonate products.
SCLEROTINA SHOOT BLIGHT OF FORSYTHIA was diagnosed twice last week-- from a homeowner sample and one from my yard. Look for dead shoots that often have an orange discoloration. The fungus infects the blossoms and flower stalks, then grows into the twigs and kills them for some distance. The black sclerotia (fungus fruiting bodies) develop inside the infected twigs and are the best diagnostic sign at this point. Prune and destroy dead twigs and stems.
OAK LEAF BLISTER caused by the fungus Taphrina is a common disease during wet seasons of many oaks in the red oak group but mostly pin oak and red oak. The fungus overwinters in infected buds and infects the newly emerging leaf tissue. Symptoms include scattered circular raised areas of varying sizes up to ½ inch over the upper surface of the infected leaves causing a depression on the corresponding lower leaf surface. Lesions are yellow-green when new and brown with age. This disease causes no defoliation and rarely requires chemical control.
Information from Bob Mulrooney, Extension Plant Pathologist, UD
Oak leaf blister. Photo by Michael Kangas, NDSU - North Dakota Forest Service, Bugwood.org
Powdery mildew on Phlox leaf. Photo from Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org
Cedar-Quince rust on Hawthorn. Photo from the Purdue University Plant Diagnostic Lab.
Cedar-Quince rust on Hawthorn twig. Photo from the Purdue University Plant Diagnostic Lab.
Friday, June 19, 2009
Cottony scales get their name from long, white egg sacspresent now. They all cause sooty mold and isolated branch dieback. For ID check the host range and egg laying site.
Cottony maple scale (Pulvinaria innumerablis) occurs on several plants, but particularly silver maple and hickory. Adults and eggs are almost always found on stems and branches, with crawlers settling on leaves for the summer until they migrate back to the stems to overwinter as female scales. Crawler peak is 1388 GDD.
Cottony maple leaf scale (Pulvinaria acericola) occurs on many plants, but most often on maples, dogwoods, black gum, and Pieris. Adults and egg masses are found all over the plant, but mostly on the leaves. They migrate twice after the crawler stage once back to the twigs in the fall and then from the twigs to the leaves in the spring. It is often confused with cottony maple scale (above) or maple mealybug (Phenacoccus acericola), which does not injure plants as severely as cottony maple leaf scale.
Cottony camellia/taxus scale (Chloropulvinaria floccifera) occurs on hollies, sweet box, Cephalotaxus, and its namesake hosts. Like cottony maple scale, it has two migrations per year and the adult females dry up and die after laying eggs leaving only the cottony egg mass on the leaf. Egg hatch from a single mass can take place over 6 weeks. Crawler peak is 830 GDD.
Many predators and parasites feed on these scales; and provide some control. Crawler treatments are the best option as hort. oil in the dormant stage and foliar treatments directed at the remigrating females are ineffective. For cottony camellia/taxus scale, two treatments of horticultural oil at ½ egg hatch and complete egg hatch (~3-4 weeks later) provides the best control with minimum impact on natural enemies. Spring-applied soil systemic neonictinoid insecticides (i.e. Merit, Safari) are also often utilized.
Information from Casey Sclar, IPM Coordinator, Longwood Gardens
Cottony Maple Leaf scale. Photo from North Carolina State University.
Cottony Camelia scale. Photo from the University of Maryland.
Cottony maple scale (Pulvinaria innumerabilis) on a silver maple (Acer saccharinum). Photo by Eugene E. Nelson, Bugwood.org.
Thursday, June 18, 2009
Minute Cypress Scale
Examine Leyland cypress in June for yellowing, dieback and presence of white scale covers that look like snow flecking on the needles. Crawlers just started emerging on June 8.
Control: Since the crawlers are just emerging 0.5 % horticultural oil and Distance or Talus would be good materials to apply.
Japanese Maple Scale
We have been monitoring the Japanese maple scale for the last couple of weeks since so many people are interested in when the crawlers start showing up. Crawlers have emerged.
Control: In the next week or so you might want to apply the IGR Distance. Many growers are mixing Distance with 0.5 - 1.0 % horticultural oil.
We examined a sample of arborvitae that had Fletcher scale and found that the crawlers have emerged.
Control: You can use Distance when crawlers emerge. Another option is soil applications of imidacloprid.
Information from the June 12, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.
Wednesday, June 17, 2009
Another two weeks of rain, hail, and wind have caused trouble throughout Delaware. Where will it end?? Trees suffering severe injury as a result of these storms aren't always the luck of the draw. Certain tree species are much more susceptible to damage than others. For instance, silver maples, willows, and ornamental pears can suffer considerable damage. Oaks and many evergreens may sustain only light damage.
Other factors that play a part in storm damage include age and maintenance history of the tree. Large old trees, improperly pruned trees, and those trees with narrow crotch angles can be particularly susceptible to damage. Severe injury can reduce the life of a tree. Wounds caused by storm injury can provide an entrance point for decay organisms and insects. Wounds can also disfigure the tree or ruin its intended function.
If your tree has been damaged, carefully examine the extent of damage. Give immediate attention to trees that are hazards to people or property. If a power line is involved, utility company personnel are the only ones who should be working in the area. After the elimination of hazardous situations, individual tree care can be assessed. Unfortunately, assessment is a judgement call with a large gray area. Severe splitting of the main trunk or an injury that removes more than 1/3 of the bark around the tree is a wound that few trees can survive. Broken tree tops are also severe injuries. Injured trees take time to heal. Repair methods are geared toward assisting the tree in healing as quickly as possible.
Most repair work involves pruning. Use correct pruning techniques to minimize the size of the wound and avoid flush cuts. Remove large, uneven stubs by pruning back to an undamaged side branch. Wound dressings are not recommended. Cabling and bracing may be appropriate if the cost involved can be justified. This method of repair does not save trees with extensive structural damage.
Many landscapers can handle work related to minor storm damage, tree care specialist may be necessar for complicated jobs. For minor damage on small trees a landscape with knowledge of proper pruning procedures, access to proper equipment, and desire can handle the job. Severe damage is better left to someone who specializes in this area. When contracting repair work out, both the homeowner and the tree service professional must clearly understand the work to be done and the cost involved. In areas that have received considerable damage, repair professionals may be heavily booked. It may take some time before they can get to a site. It's important to keep people away from potentially dangerous situations until the necessary work is completed.
If tree replacement ends up being your only alternative, select tree species and cultivars with a sturdy reputation. Avoid species noted for being damage in storms - those with weak wood, ingrown bark problems, those with excessive rapid growth, and those with weak and shallow root systems.
Adapted from an article by Sherry Rindels, Department of Horticulture, Iowa State University.
Inventory: By keeping track of trees on your property and their condition, predicting storm failure is much easier. Create a list of "key trees and key problems." Key trees would be those that are most important to the property. Key problems would be those that are most likely to damage or weaken those key trees.
Monitor: Check key trees regularly. When minor damage occurs, correction (such as pruning out damaged material) may prevent it from causing extensive damage throughout the tree. If extensive damage has occurred, immediate corrective action should be applied to prevent further damage.
Proper Pruning: Pruning either corrects problems or creates them. If pruning is done improperly, it can create places for decay to enter and the wound will only increase in extent. Done correctly, pruning wounds should close over naturally, keeping decay from starting and expanding in the wound area. A general rule for pruning wounds: the smaller, the better.
Protection From Mechanical Wounding: Mulching, planting trees in landscaped beds, and even staking can give trees the necessary protection from mechanical injury. Wounds caused from lawnmowers and grass trimmers can promote areas of decay in the tree. Any actions that causes wounds on stems and branches can cause long-term damage in a short time.
Appropriate Species: Using appropriate species in each site is extremely important. Many of the problems that homeowners face could be diminished just by using species that are native to the area or accustomed to the site conditions. For instance, an upland forest tree (such as white pine) will never be healthy and stable if planted in compacted, poorly-drained soils. A tree adapted to moist soils will do poorly in droughty areas.
Best Planting Practices: Planting too deep may be the most common planting mistake that leads to tree failure. Literature is available on proper planting techniques. Most importantly, do not plant the tree too deep. The first set of roots should be just below the soil surface.
Adapted from "Storm Damage to Landscape Trees: Prediction, Prevention, Treatment" by Gary R. Johnson, Associate Professor, Urban and Community Forestry, Ben Johnson, Undergraduate Research Assistant, Department of Forest Resources, University of Minnesota.
Tuesday, June 16, 2009
There is no way, except for complete enclosure, to protect trees from all storm damage. Trees are not adapted to worst-case storms -- only to our average wind climate. Listed are several things to minimize the main types of storm damage:
Let trees adjust to the wind environment. Tight staking and guying from the time of planting holds a tree in place while preventing internal adjustment to wind loading. Always stake and tie the tree loosely where the stem can move and bend in the wind. Keep ties in place for a few growing seasons to ensure a well-established root system. Continue to loosen and, eventually, release the ties. Leave the support stakes in place to protect the stem from mechanical damage. After five to seven years, remove all tree support. The tree will continue to grow and adjust to its new environment.
Practice proper pruning techniques by cutting branches before they become larger than 1 inch in diameter. Do not damage the branch collar (Figure 1). The branch collar is part of the stem and, if damaged by poor pruning, provides an avenue of attack into the main stem for pests. Proper pruning minimizes a number of structural problems that occur in association with new wood growth around a pruned branch.
Eliminate co-dominant branches. Prune forked branches and branches that arise opposite each other on the stem early. Cut one side off now to prevent loving the whole tree later if it splits in a storm. In trees with opposite branching patterns (such as ash or maple), proper branch training is essential for a long-lived, storm resistant tree.
Keep trees as healthy as possible with timely watering and proper fertilization. Healthy, vigorous trees adjust more quickly to changes in the environment, are more wind firm and react more effectively to damage.
Do not over-fertilize the tree with nitrogen or over-water the soil. This can increase the crown surface area and/or decrease the rooting area. This type of biological change makes the tree susceptible to storm damage.
Eliminate lopsided crowns. Prune branches to produce a reasonably symmetrical crown. If more than 70 percent of the crown is on one side of a mature tree, consider tree removal and replacement. Guying and bracing branches are last-ditch efforts when a tree has to be saved in spite of itself.
Remove or treat pest problems such as branch cankers to minimize potential damage. Do not over-treat tree hollows. Do not remove decayed wood from hollows unless it falls away in your hands. Cleaning hollows can lead to further internal damage. Cover the openings to hollows to allow the tree to grow over the opening; covering also prevent animals from expanding the hollow and keeps water from running in.
Keep the tree growing upright with one main stem. Prune away branches that compete in height with the main stem. Eliminate branches with tight or narrow crotches.
Install lightning protection systems on historic, rare, specimen or recreational area trees. Consult a qualified arborist or urban forester to ensure adequate design. Lightning protection systems are covered in detail in the section "Lightning Protection Systems."
Continue to promote wind firmness by not over-crowding trees and by proper guying and bracing. A tree must always be able to move in the wind. Do not keep a tree tied into position with tight cables. In a stand of trees, slowly remove trees over a number of years to allow wind firmness to develop in the remain-ing trees.
Information from "Storm Damaged Trees: Prevention and Treatment" by Kim Coder, Professor Silvics/Ecology, Warnell School of Forest Resources, University of Georgia. Go to http://pubs.caes.uga.edu/caespubs/pubcd/C806.htm for the full fact sheet.
There are six main types of storm damage to trees:
(1) blow-over, (2) stem failure, (3) crown twist, (4) root failure, (5) branch failure and (6) lightning. Each type is the result of a complex and interactive mix of tree problems and climate.
With blow-over, the tree is physically pushed over by high winds. Little biological adjustment is available for a tree (or for people) to make to hurricanes, down-drafts or tornado winds. The wind force on the aerial tree portions is too great for the wood structure. Past tree abuse, poor maintenance, pest problems (like fusiform cankers on pine or root rots on hardwoods) predispose the tree to storm damage by weakening the wood architecture.
Trees do not heal wounds. Trees can only grow over old wounds and seal them off. This results in a tree carrying in its wood every injury it has ever had. These old injury sites -- and the old and new wood around them -- are structurally weaker than normal solid wood. These damaged areas can quickly fail under a constant wind loading and release. Pest damage, weak wood around old wounds, new wounds and failure of the tree to adjust to wind conditions can lead to stem failure under heavy wind loading and release.
For trees with heavy crowns, abrupt wind gusts and calm periods can lead to stem breakage from release. As the wind load is quickly released, the tree moves back into an upright position. If the mass of the crown moves too quickly when released, the inertia of the moving crown may move too far in the opposite direction leading to stem damage and breakage.
Tree crowns are the leaves and supporting twigs and branches. Trees are never perfectly symmetrical in every direction. Many trees, through past abuse and poor management, have lopsided crowns. More wind loading on one side of the crown than on another produces a twist (torque) on major branches and the main stem. Over time, the twisting effect can be biologically adjusted from within the new wood. Stem twisting will magnify weaknesses around old injuries and the stem will split or branches collapse.
There are two types of tree roots: fine, absorbing roots and woody, structural roots. As their names imply, ab-sorbing roots have a massive surface area but are weak. Structural roots are woody, have a relatively small sur-face area, but are strong. Both types provide anchorage for a tree. The primary roots growing from the bottom of the stem (root collar) play dominant roles in holding the tree upright while conducting water, essential elements and nutrients. If roots are constrained, diseased or dam-aged by construction or -- as the top of the tree becomes larger -- greater stress is put on the roots. Pulled or snapped roots cause trees to fall or lean.
Branches are poorly attached to the main stem. A branch is stuck on the side of the stem each year by a small layer of stem wood called the branch collar. The branch collar surrounds the branch base. The woody material from the branch enters the stem and turns downward. This structural arrangement allows the branch to be flexible and disposable. The stem can shut off the branch when the branch becomes a biological liability to the tree.
Heavy loading (as during an ice storm) puts great stress on the branch collar area. Over many years, a tree will adjust to this stress, but ice storms or downbursts that occur only rarely will leave the branches unprepared and susceptible to tearing downward along the stem or snapping. The branch collar area can also be weakened by included bark. This material is bark from both the expanding stem and branch. Where the branch and stem expand against each other, bark can be surrounded and overgrown inside the branch collar area. Included bark leads to weaker structure and a place for pest attack. This is why forks (called co-dominant branches) are structurally weak. These weak areas can easily fail in a storm.
Lightning damage is a life-threatening situation. Lightning either moves in a narrow line down the branches, stems and roots or along a wide pathway encompassing the entire tree cylinder. Lightning directly destroys tree tissues by electrical disruption and heat. Steam explosions down the stem in a wide or narrow band show where the electrical current has moved through the tree.
Massive root damage can remain unseen. Damage caused by lightning leads to extensive water loss that is also life-threatening. Pests quickly attack a lightning weakened and damaged tree. For example, the Southern pine beetle quickly destroys a lightning struck pine.
Information from "Storm Damaged Trees: Prevention and Treatment" by Kim Coder, Professor Silvics/Ecology, Warnell School of Forest Resources, University of Georgia. Go to http://pubs.caes.uga.edu/caespubs/pubcd/C806.htm for the full fact sheet.
Monday, June 15, 2009
It is not unusual for roses to "change color." A minor change occurs when cooler weather intensifies pink-to-red shades, or age and hot weather fade them. Knock Out ‘Blushing’ rose flowers, for example, are medium pink in cool springs like this and in fall, but a washed-out, nearly-white in summer. The 'Rainbow' and 'Sunny' Knockout rose marketing capitalizes on the fading of pastel pink and yellow petals as they age, emphasizing that at any one time there are deeply colored buds, pastel newly opened flowers, and pale to off-white older blossoms. The contrast is greatest, and those plants are most attractive in cool weather. Some of our Master Gardener volunteers have complained they are quite disappointed in the "washed-out" summer appearance of those varieties.
The second type of color change is due to the fact many roses are grafted, so the branches are one variety and the lower root system is a hardier rose. If those lower roots sprout branches, they may appear different in leaf size, shape and flower color. They are more likely to have such sprouts when planted shallow, or if the top branches are all killed by cold temperatures. The variety used for the hardy rootstock will survive cold damage but the grafted top may not. Roses may start out with branches and blossoms of a different variety such as a less hardy tea rose and end up with only the hardy root stock if the less hardy grafted top is killed out.
Adapted from an article in the Landscape Advisory Team Alert from Michigan State University:
The weather continues to be very favorable for leaf diseases previously covered--Crabapple scab, anthracnose on sycamore and ash, spot anthracnose on flowering dogwood, cedarapple rust. Frogeye leafspot on red, silver and Japanese maple is caused by a fungus called Phyllosticta and is also very evident. A different species of this fungus causes a major leaf disease of witchhazel especially the hybrids (Hamamaelis x intermedia 'Arnold's Promise' and others). Leaf blight of witchhazel causes necrotic spots and can kill leaves of susceptible cultivars. The spots are irregular but when they coalesce they can blight entire leaves, often confused as leaf scorch from drought. In wet years like this, it can disfigure the shrubs. In most cases it is too late for fungicide control but raking and composting of infected leaves may reduce the amount of fungus for next season.
Sunday, June 14, 2009
Continue Watching Out for Downy Mildew
Cool, wet weather of the past few weeks has been favorable for the development of downy mildew on coleus. Symptoms on leaves range from small brown blotches to angular brown lesions to distortion and defoliation, depending on cultivar. Symptoms of downy mildew can mimic symptoms of Botrytis blight, drought stress or nutritional problems, so it’s important to get a confirmed diagnosis if you suspect downy mildew. The photo shows symptoms on Helichrysum. Growers can expect to find this disease in seed and vegetatively propagated types of coleus. John Speaker, IPM Scout, noted that he usually find it in vegetatively grown coleus first. If it shows up there it will spread to seed grown coleus. The fungus reproduces via specialized spores called sporangia. If you examine the undersides of the foliage you may sometimes see the gray colored sporangia on the underside of the coleus leaves. In some instances, these sporangia may be few in number and very difficult to see without the help of a microscope. Other times, the sporangia are produced in high numbers and form a fine carpet of grayish fuzz on the underside of the leaf that is obvious to the naked eye. It is best to look for these sporangia when the greenhouse environment is humid and damp.
Downy Mildew Control: Check all incoming coleus plants and cuttings for symptoms of the disease. Cultural practices that reduce humidity in the crop (increased air circulation, increased plant spacing) can help reduce spread of the disease. Discard infected plants by placing in plastic bags before carrying them out of the greenhouse to avoid spreading sporangia during plant removal. An effective protectant fungicide program includes rotating between Stature (dimethomorph), Fenstop (fenamidone), and mancozeb products (such as Protect DF). After the crop is finished, remove plant debris and wipe down surfaces with a greenhouse disinfectant. If you’ve had a problem with coleus downy mildew, make sure to discard any coleus stock plants to keep the disease from surviving in your operation until your next crop.
Information from the June 12, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center
Growers of garden mums are reminded to monitor for and take precautions against Chrysanthemum white rust (Puccinia horiana), especially during cool, wet weather. Train staff to recognize symptoms and monitor plants throughout the growing season since infections can appear at any stage in crop production. Symptoms are distinctive. The first symptoms of white rust are yellow spots on upper leaf surfaces. These may become sunken and necrotic. Anyone not familiar with this disease might confuse these early symptoms with spray or insect damage. Any sign of yellow spotting should be closely examined for further evidence of this disease. Diagnostic symptoms appear as raised pink or white waxy pustules on the undersides of the leaf. Severely infected leaves dry up and persist on the stems. Infected plants may remain symptomless for weeks, especially during hot and dry conditions. Symptoms usually appear during cooler, wet weather.
Fungicide applications may suppress disease development. Protectant fungicides include: Azoxystrobin (Heritage), Chlorothalonil (Chlorothalonil, Daconil, Echo, Spectro 90 WDG with thiophanate-methyl), Kresoxim-methyl (Cygnus), Mancozeb (Fore, Dithane75DF, Protect DF, Pentathlon), Myclobutanil (Eagle 20 EW), Triadimefon (Strike), Triflumizole (Terraguard). Always read and follow label directions. The label is the law.
Keep susceptible varieties away from others. Varieties that have tested positive for chrysanthemum white rust (CWR) in the past few years include several ‘Gretchen’™ cultivars (’Bold’, ‘Bright’, ‘Flashy’, and ‘Sunny’), as well as the cultivars ‘Dark Veria’™ ‘Debonair’,™ ‘Ashley’,™ ‘Vicki’,™ ‘Okra’,™ ‘Cesaro’,™ and ‘Flamingo Pink’™ , ‘Gold Finch Yellow’ , Pink Symphony’, ‘Bold Melissa’, ‘Canelli’, ‘Heidi’, ‘Beth’, ‘Helen’, ‘Canelli’, and ‘Galatino’ that are not in the ‘Gretchen’™ series. In addition, cultivars not specified tested positive in a wide range of colors and types (some of which were grass-mum combination pots). Chrysanthemum white rust infects 12 species of chrysanthemum, including garden mums, pot mums, and Nippon daisies.
CWR is still, (at this date) a regulated pest of quarantine significance. If CWR is diagnosed, state and federal regulators remove and destroy infected plants from sites in compliance with the CWR Eradication Protocol established by the USDA APHIS-PPQ.
What to do if you see this disease:
Call the Plant Industries Section of the Delaware Department of Agriculture (302) 698-4500. Regulatory personnel will supervise the eradication and treatment procedures.
Chrysanthemum White Rust.
Information reprinted from the current edition of the New England Greenhouse Update http://www.negreenhouseupdate.info/greenhouse_update/index.php
Saturday, June 13, 2009
State gypsy moth programs and some landscapers have observed that gypsy moth seems to prefer blue spruce. This is especially true when populations of gypsy moth drop in an area - gypsy moth still will be concentrated on blue spruce. It is common to see little or no caterpillar feeding on oaks or any egg masses present on the oaks while a blue spruce nearby can be loaded with gypsy moth larvae. When they pupate and emerge the adult females tend to lay eggs on the blue spruce. The gypsy moth larvae are large and in the last instar stages at this time of year. If they are on spruce they would be doing major defoliation at this point. The take home message: If your customers have blue spruce, examine them closely for the presence of gypsy moth populations. There is something about blue spruce that is highly attractive to gypsy moths.
Adapted from the June 12, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers University of Maryland Cooperative Extension
Bagworm larvae are hatching, ballooning or feeding. Look for the 'dunce-cap' stage of feeding that occurs when larvae are very small and carry their bags with them in an upright position. Bagworm hatch occurs between 364 and 710 GDD (peaks at 580). Bagworms are caterpillars that prefer to feed on juniper, arborvitae, and Leyland cypress, but will eat a variety of other deciduous and coniferous plants. The bag is made up of small pieces of the plant the bagworm is eating and silk. The bags may look like pine cones or parts of the plant; thus it often is overlooked until damage becomes severe.
Larvae feed throughout the summer and begin to pupate around mid-August. Female bagworms pupate but remain in a flightless caterpillar-like state and release pheromones to attract males. Female bagworms lay 300 to 1,000 eggs in the bag after mating and die. The following summer the overwintering eggs hatch and disperse by ballooning on the wind to nearby plants. Although there is only one generation a year, damage may be encountered throughout the summer.
One control tactic is to physically remove the bags late fall through spring, but this is often too labor intensive or impractical because of tree or shrub size. Companion plants encourage parasitoids to remain in the area to attack bagworm pupae. Last summer, John Wiest and I evaluated the efficacy of Orthene (acephate), Dipel (B. thuriengensis 'kurstaki'), Conserve (spinosad) and Acelepryn (chlorantraniliprole) applied in late July without stickers. We discovered Acelepryn and Orthene provided similar levels of control (> 75%) whereas Conserve and Dipel provided less control of large bagworm larvae. Most bagworm eggs have hatched by middle to late June and applications of pesticides should be applied by July to target early instars. Products are more effective against smaller, younger caterpillars. Other products available include Confirm, Tempo, Permethrin Pro, or other pyrethroids.
Information from Brian Kunkel, Ornamental IPM Specialist, UD
Friday, June 12, 2009
Now is the time to initiate an effective chemical and cultural control program for summer patch. This disease of Kentucky bluegrass and creeping red fescue is caused by the fungus Magnaporthe poae and can be controlled through the use of good cultural practices and the application of a penetrant fungicide. For best results, maintain soil pH at or slightly below 6.0, fertilize turf with ammonium sulfate (during cool weather to avoid phytotoxicity) or sulfur-coated urea, avoid the use of nitrate-based fertilizers (which can enhance symptom severity), and aerify (before symptoms develop) to reduce compaction and decrease disease severity. Fungicides are most effective when applied in mid- to late-May (i.e., when the soil temperatures at a 2 inch depth exceed 65 0 F for 5 to 6 consecutive days) and then repeated two additional times at 28 day intervals. To optimize control, apply Armada, Banner, Bayleton, Compass, Disarm, Eagle, Headway, Heritage, Insignia, Rubigan, Tartan, thiophanate- methyl or Trinity in 4 to 5 gal water/1000 ft. If products are delivered in lower water volumes (e.g., 2 gal water/1000 ft2), irrigate with 1/8 inch of water immediately following application to enhance disease control.
Reprinted in part from "Diseases of Turfgrass" by Bruce B. Clarke, Ph.D., Specialist in Turfgrass Pathology in the May 28, 2009 edition of the Plant and Pest Advisory newsletter, Landscape, Nursery and Turf Edition from Rutgers University.
Controlling spider mites and protecting spider mite predators
The use of Horticultural Oil is still an excellent choice as a miticide when adequate coverage can be achieved and infestations are moderate. When the time and effort is taken to apply a thorough oil spray application against a population of mites, the results are usually satisfactory. Oil suppresses three stages of the mite life cycle (egg, immature, and adult). It also has less impact against predatory mites (as well as other predators) than do most traditional miticides.
When using miticides, the objective is to maximize your control of the pest mites and eliminate friendly fire to the predatory mites. Fortunately, several recently developed miticides have this unique ability. Examples of these new materials include Hexygon and Tetrasan. These materials are now registered for use on exterior ornamentals and they control the eggs and immatures of only spider mites (neither eriophyid nor predatory mites are affected). Both are “mite growth regulators” and inhibit the formation of chitin, the building block of the outer exoskeleton. Floramite is another miticide impacting only spider mite pests. It controls adult mites and provides egg suppression against two-spotted spider mites. Furthermore, all of these miticides have at least a three-week residual.
Hexygon and Tetrasan do have potential disadvantages since they do not control adult spider mites. Therefore, a large infestation of spider mites treated with these materials may continue to feed as adults and cause damage for two weeks or more before a majority of the population dies off. Observations using Hexygon indicate that treated adult female mites become sterile and any laid eggs do not hatch. Horticultural Oils are compatible with Hexygon and Tetrasan can be mixed together to provide reinforcements to suppress the adults.
Reprinted from "Landscape IPM Pest Notes" by Steven K. Rettke, Ornamental IPM Program Associate in the May 28, 2009 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University.
Thursday, June 11, 2009
Bacterial Shoot Blight or Syringae blight is caused by a bacterium Pseudomonas syringae and its many pathovars. It can cause leaf spots, blights and cankers on susceptible hosts. This disease has been very active in the landscape on many hosts especially lilac, cherries, rose, apple, pear, willow, and photinia. Sometimes the damage on cherries and lilac can resemble fire blight on apple. On green twigs, lesions can appear as black streaks. On lilac, green shoots die, turn black and shrivel. Leaf spots are irregularly shaped, brown and often with yellow halos. Once the dieback dries out, the damaged stems can be pruned out. There are no effective chemical controls in the landscape. Applications of copper containing fungicides and streptomycin could reduce epiphytic populations of the bacteria in production nurseries during wet seasons, but for the homeowner it is probably best to wait it out and prune.
Symptoms of bacterial blight (Pseudomonas syringae) on leaves of a lilac. Photo by William Jacobi, Colorado State University, Bugwood.org.
Signs and symptoms of bacterial blight (Pseudomonas syringae) on a lilac. Photo by William Jacobi, Colorado State University, Bugwood.org.
Information from Bob Mulrooney, Extension Plant Pathologist, UD.
- If you have not done so already, apply the second application of preemergence crabgrass herbicide (such as pendamethalin) to turf with a crabgrass problem. There may already be crabgrass breaks with all the wet weather and a postemergence material will be necessary in that case (such as fenoxaprop or quinclorac).
- Wet weather will promote yellow nutsedge growth. Postemergence herbicides with activity on nutsedge include halsulfuron , sulfentrazone , and bentazon. All 3 can be used in turf; halsulfuron and bentazon can be used around some landscape plants (check the label). Glyphosate and glufosinate can be used as a directed, wiper, or spot spray application in landscapes. Two applications are often needed with bentazon, glyphosate, or glufosinate for effective nutsedge control.
- Summer annual weed escapes in landscape beds will be evident. Hand weeding is often the only option. Directed applications of glyphosate, glufosinate, or pelargonic acid herbicides can be used where there is space between desirable plants. Post emergence grass herbicides (fenoxaprop, clethodim, fluazifop-P-butyl, and sethoxydim) can be used over the top of many landscape plants where annual grass weeds are dominant.
Wednesday, June 10, 2009
One management strategy to consider is a sequential application of these herbicides 6 to 8 weeks apart. As an example, say you plan to apply a crabgrass/ goosegrass control product containing the active ingredient pendemethalin at 2.0 to 3.0 pounds of active ingredient per acre. You may want to consider an April application at 1.0 to 1.5 pounds of active ingredient followed by a second application in late early June of another 1.0 to 1.5 pounds. Although this will increase labor inputs, a sequential application will help insure that crabgrass and goosegrass will be controlled into the summer, eliminating the possible need for a postemergence herbicide application.
If crabgrass escapes are found, add a postemergence material along with the preemergence material (such as Acclaim Extra or Drive).
Information from Dr. Steve Hart, Rutgers University (italics from Gordon Johnson, UD).
Yellow nutsedge (Cyperus esculentus) is a troublesome sedge weed in turf and landscape beds, particularly in irrigated and wetter areas. Heavier nutsege infestations will occur in wet years. It 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 applied preemergence has provided good control in landscape beds. Halsulfuron applied post emergence has provided excellent control in established woody landscape plantings and in turf. Sulfentrazone gives excellent post emergence yellow nutsedge control in turf and is effective against many other sedges (annual and perennial) such as Kyllinga. Bentazon 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
Tuesday, June 9, 2009
Compared to armored scales, the soft scales are relatively easy to suppress with either contact sprays or systemic treatments. Some of the common landscape soft scale species include Calico, Fletcher, Wax, Terrapin, Cottony Maple, Lecanium, Cottony Taxus, Pine Tortoise, Striped Pine, and Spruce Bud. Although large soft scale adult females are more difficult to control, the immature nymphs are highly vulnerable to sprays when good coverage is achieved. There are numerous windows of control opportunities when applying sprays or systemic treatments against soft scales. The best window for control when using spray treatments is toward the crawler emergence period. With only two major exceptions (Magnolia & Tuliptree scales), all other soft scale species produce crawlers during the months of June or July. Although scale crawlers are only 2 to 3 times the size of spider mites, they are usually clearly visible without magnification. Most crawlers have a yellowish or reddish coloration. Sprays can also be successfully targeted against the settled 1st instar nymph stage feeding on foliage or bark during the growing season. Achieving adequate coverage to foliage is the major challenge with large deciduous shade trees since the settled nymphs feed on the undersides of leaves along major veins. In addition, dormant oil treatments can be applied in the late fall or early spring to the over-wintering 2nd instar nymphs on deciduous hosts. These nymphs have a black or brown coloration and are considerably larger than the crawlers and 1st instar nymphs. They can be observed in clusters on the bark of twigs, branches or trunks. Finally, since soft scales are vascular feeders (phloem or xylem), root absorbed systemic insecticides such as imidacloprid (Merit) or dinotefuran (Safari) have provided better than 90% control rates. Root systemic treatments can be applied as a drench or be soil injected any time during the year as long as the ground is not frozen. Fall or spring applications are most typical. Having adequate soil moisture is a key factor to ensure success when applying root systemic treatments.
Information from Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University.
Many arborists and landscapers often suggest to their inquiring clients that frost-cracks are the reason for the bark separation within the trunks of trees. Often times, however, the actual cause may be from drought stress. Drought-cracks occur most commonly when trees are first planted and a year or so after transplant. The trunks will crack if trees are allowed to become too dry. Some common trees more susceptible to this condition include maple, honeylocust, crabapple, mountain ash, and London-plane. One of the easiest ways to distinguish between a drought or frost crack is by the way a wound closes. Drought cracks typically represent a one-time event and will generally close or seal almost completely and never re-open again. On the other hand, frost cracks are more likely to continue to open and close over subsequent years. Usually less freezing and thawing stress is required to re-open the crack in the future and the development of a conspicuous callus ridge often occurs over time. Sunscald wounds occurring on the south or southwest sides of tree trunks can also create cracks (i.e., frost or drought cracks can occur on trunk sides facing any direction). Sunscald wounds generally never close or seal over and may often increase in size as the tree grows. Although there is rarely any need for immediate concern when managing trees with these types of trunk cracks, the open wounds can increase the potential exposure to wood decay fungi.
Information from Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University.
Monday, June 8, 2009
Fire blight is a relatively common disease caused by a bacterium (Erwinia amylovora). Fire blight can occur on many rosaceous plants, including crabapple, cotoneaster, hawthorn, mountain ash, pyracantha, and pear. Although we see this disease most often in pyracantha, some ornamental pears in central New Jersey have been recently diagnosed with the disease. Development of fireblight usually begins in the spring as bacterial cells ooze in a yellow-amber liquid from existing cankers on infected plants. These cells are spread to susceptible flowers, leaves, fruit, and stems by insects, wind, splashing rain, or pruning equipment. Insects are especially attracted to this sweet, sticky, bacterial ooze; bees and other pollinating insects commonly pick up bacteria while visiting the cankers and subsequently deposit the cells on developing flowers. Erwinia bacteria penetrate tissue through wounds and natural openings such as stomates and nectaries. Twigs and branches infected with the pathogen die rapidly and appear scorched, hence the name “fireblight.” Tender shoots tend to droop and bend as they die, developing a symptom commonly associated with the disease called a shepherd’s crook. As the disease advances, cankers form at the base of infected branches, and highly susceptible plants may die. Conditions optimal for fireblight development are extended periods of warm (greater than 65 to 75 F), wet weather during spring.
To manage the disease, improve plant vigor, but avoid heavy spring fertilization that would promote succulent growth. In late summer (after bacterial oozing no longer occurs), prune all diseased wood at least 6 to 8 inches below the infection, surface sterilizing tools between cuts. Remove water sprouts, and dispose of any infected plant material which may harbor the pathogen. The following bactericides have labels for fire blight (check for host, timing, and rates): copper (Badge, hydroxide, metallic, salts, sulfate), fosetyl- Al (pre-bloom and repeat every 7 days until bloom), Junction (5-day intervals during bloom), OR phosphite (7-day intervals through bloom). Finally, consider repeatedly diseased, highly susceptible plants with material that is more resistant to this disease. Highly susceptible callery pears include Aristocrat, Autumn Blaze, Capital, Fauriei, and Redspire; moderately susceptible cultivars include Cleveland Select, Earlyred, and Whitehouse. Although Bradford is reported to be moderately resistant in certain locations, it will develop fireblight under conditions optimal for disease development, as we noticed last year.
Fire blight on ornamental pear. Photo from the Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org.
Information from Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University.
This disease, caused by the fungus Rhizoctonia solani, will be starting to develop later in June on turf. To reduce the incidence and severity of brown patch, avoid applying too much nitrogen (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, Banner (preventive only), Chipco 26GT, chlorothalonil, Compass, ConSyst, Curalan, Disarm, Eagle, Endorse, Headway, Heritage, Insignia, mancozeb, Medallion, ProStar, Spectro, Tartan, thiophanate-methyl, Touche or Tourney per manufacturer’s recommendations.
Information from Bruce B. Clarke, Ph.D., Specialist in Turfgrass Pathology, Rutgers University