Landscape, Nursery, and Greenhouse - Whiteflies

The following is information on whiteflies that you may see on plants in Delaware.

Whiteflies affect both woody and herbaceous plants. Whitefly damage starts with yellowed foliage follwed by honeydew/sooty mold. Almost all stages, except the egg and last nymphal stage (aka “pupae”) feed. The following represents a few of the common whiteflies in our area, their level of impact and ID tips.

Azalea/Rhododendron Whitefly (Pealius azaleae, Dialeurodes chittendeni) Occasional pest that causes leaf cupping and minor leaf yellowing. Nymphs/”Pupae” orange to yellow. Nuisance clouds of dusty colored adults can be heavy at times.

Banded Winged Whitefly (Trialeurodes abutilonia) Adults hold wings “peaked” over body (similar to silverleaf whitefly), with two dark grey bands on each wing. “Pupae” slightly brownish in color. Often found on yellow sticky cards, but cause no damage to most ornamentals.

Greenhouse Whitefly (Trialeurodes vaporariorum) Common, many hosts affected. Live nymphs yellow. Differ from silverleaf whitefly--adults fold wings flat on top of their body and “pupae” resemble “fluffy pancakes” with raised sides. Often require management.

Mulberry Whitefly (Tetraleurodes mori, T. ursorum) Affect mulberry, citrus, Mahonia and a few other woody species. Nymphs are black surrounded by a white fringe. Rarely more than a curiosity.

Silverleaf (Sweetpotato) Whitefly (Bemisia argentifolii, B. tabaci) Common, many hosts affected. Nymphs yellow colored. Differ from greenhouse whitefly--adults fold wings flat on top of their body and “pupae” resemble “yellow water droplets” without any raised sides. Very common on recently purchased or introduced plants. Require management. New Biotype Q of this pest resistant to many standard pesticides, esp. Distance (pyriproxifen) and neonicotinoids.

For whitefly species requiring management, choose selective products that target specific life stages like horticultural/neem oils and IGR's for nymphs, Beauveria or neonicotinoids for late nymphal stages, and target adults only if necessary with pyrethroids. Predators and parasites exist in the landscape environment or are available to purchase for greenhouse/nursery environments. Look for black “pupae” in Greenhouse/Silverleaf whitefly infestations that indicate parasitism.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale IX

This is a continuation of the series on plants for Delaware landscapes featuring those being offered at the Fall UDBG plant sale.

Rudbeckia subtomentosa 'Henry Eilers', sweet coneflower, native plant, sun to part shade, moist to dry soils, 4-5', finely quilled yellow flowers from July to September, hummingbirds & butterflies love the flowers.

Salvia 'Eveline', garden sage, sun, moist soils, 24-30", tall upright spikes of bicolor pink flowers; lush green foliage

Photos from North Creek Nurseries who provided the plugs. Go to http://www.northcreeknurseries.com/ for more information. This is a great source for perennial plugs featuring many natives for this region.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale VIII

This is a continuation of the series on plants to consider for Delaware Landscapes featuring those being offered at the Fall UDBG plant sale.

Hibiscus coccineus, scarlet rose mallow, native plant, sun to part shade, moist to wet soils, 5-8', deep red 6" flowers; deeply cut foliage that is red in fall, resistant to Japanese beetles. Photo from the University of Georgia.

Muhlenbergia capillaris, pink muhly grass, native plant, sun to part shade, moist to dry soils, 2-3', tidy clumps very fine blue foliage, clouds of airy pink flowers lasting weeks. Photo from the Virginia Native Plant Society.

Greenhouse and Nursery - Heat and Slow Release Fertilizers in Mums

In some cases, you can get heavy release of fertilizer salts from slow release fertilizers in hot weather when growing mums. The following is information on this subject.

Hot Weather and Controlled-Release Fertilizer.

Plants fertilized with controlled-release fertilizer with pots placed on black landscape cloth can be exposed to very high temperatures for several weeks during the growing season. Very hot weather over an extended period of time can cause controlled-release fertilizer to release early, burn roots and weaken plants. Soil temperature is a primary factor affecting release of fertilizer from the prills. As the soil temperature increases above 70°F, the rate of release increases. To compound the problem, because there are very few roots, the soil remains saturated for a longer period of time. Once plants are stressed, root diseases take hold and cause a secondary problem.
In another situation, when controlled-release fertilizer releases all at once, combined with regular watering, plants recover but plants go from being over-fertilized to being underfed. The controlled-release fertilizer has released but has leached out, leaving plants deficient and hardened.

Many growers use controlled-release fertilizers without a problem. If plants are overhead watered and drip irrigation is not an option, then controlled release fertilizer may be the only solution. A split application of the controlled-release fertilizer should prevent two problems. It should prevent high soluble salts resulting from the fertilizer prills releasing fertilizer prematurely and it should prevent lack of feed due to fertilizer being leached once it has released.

Growers having a drip irrigation system may consider using a combination of half the rate of controlled-release fertilizer and supplementing with 50% liquid water soluble fertilizer or using 100% water soluble fertilizer. A monthly soil or media test should be conducted to monitor and adjust plant nutrition.

Information from "Garden Mums - Past Crop Problems and Production Tips" by Tina M. Smith, Extension Floriculture Program, University of Massachusetts Extension
http://www.umass.edu/umext/floriculture/fact_sheets/specific_crops/hardymum_problems.htm

Greenhouse and Nursery - Fusarium on Garden Mums

Fusarium wilt is a common disease of garden mums, especially field grown mums. The following is an article on the subject.

Fusarium wilt caused by Fusarium oxysporum f.sp. chrysamthemi is a vascular disease that develops within stems. The fungus is soil-borne and after entering the plant through the roots, invades the stem plugging water conducting tissue (xylem) with mycelium and spores. Fusarium wilt symptoms are often confused with root rot but plants infected with Fusarium generally wilt in sectors (one side) and roots often appear healthy. Root rot diseases usually result in the entire plant wilting. The first symptoms of Fusarium wilt are wilting leaves on one side of the plant followed by yellowing and browning of the leaves. Infected plants are stunted and often fail to produce flowers. The entire plant may wilt and die. Severe symptoms develop during warm, constant temperatures of 80-90F, only mild symptoms may appear at 70F. Fusarium wilt can survive in soil for many years and is difficult to control once it becomes established in a field or bed.


Photo and information from the New England Greenhouse Update.

Managing Fusarium wilt centers on the use of disease-free (culture-indexed) cuttings and pathogen-free root media. Other management practices include maintaining soil pH between 6.5 and 7.0, using nitrate rather than ammonium nitrogen and drenching with fungicides. Fungicides containing thiophanate methyl (Cleary’s 3336) and fludioxonil (Medallion) have been reported to suppress Fusarium.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale VII

The following is a continuation of the series on plants for Delaware landscapes featuring those being offered at the fall UDBG plant sale.

Carex flaccosperma, blue wood sedge, shade to part shade, moist to dry soils, 6-12", drought tolerant, evergreen, glaucous blue leaves, woodland ground cover. Photo from North Creek Nursery.

Chrysanthemum 'Sheffield Pink', hardy mum, sun, moist to dry soils, 1', profusion of apricot pink flowers in early fall, a very striking display.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale VI

The following is a continuation of the series of plants for Delaware landscapes featuring those being offered at the Fall UDBG plant sale.

Aster divaricatus, white wood aster, native palnt, shade to part shade, moist to dry soils, 12-30". White wood aster thrives in shade and is drought tolerant making it suitable for dry shaded areas. It has small abundant white flowers that attract butterflies.


Belamcanda chinensis , blackberry lily, sun to part shade, moist to dry soils, 2-3', vivid orange flowers with red speckles that produce ornamental black colored berries.

Turf - Time for Grub Controls

It is time to apply grub control measures in turf. The following is information on grubs and products available to control them.

Just for a quick refresher on the white grub life cycle: All of the important species have only one generation per year (annual white grubs!) that only varies by a few weeks in timing among the different species. The eggs are laid in June and July among the roots of host plants like turfgrasses and ornamental plants and hatch in 2–3 weeks. The emerging larvae go through three larval stages feeding on roots and organic matter in the soil. The first and second larval stage will last about 3 weeks each so that by late August the first third stage larvae appear. By mid-September the majority of larvae will be in the third stage. The bigger the larvae, the more they feed (more damage potential) but the less they become susceptible to most control agents. The third stage continues to feed into mid- or late October, then spends the winter inactive deeper in the soil, to come back up clofor another 4–6 weeks between mid-April and mid-June. The larvae pupate deeper in the soil and emerge after about 2 weeks as the next adult beetle generation.

If you deem preventive applications necessary, here are your current choices by insecticide class. Among the neonicotinoid insecticides imidacloprid (Merit, Advanced Lawn Season-Long Grub Control, GrubEX) has more recently been joined by clothianidin (Arena) and thiamethoxam (Meridian). Imidacloprid and thiamethoxam are very similar in activity but clothianidin seems to have a slightly wider spectrum of activity. Among these neonicotinoids, only clothianidin seems to have decent activity against the Asiatic garden beetle but should be applied at the highest allowed rate for this species. All three of them are very active against the other important white grub species although at least imidacloprid should be applied at the highest allowed rate against northern masked chafer if later in the season (past late July).

The insect growth regulator halofenozide (Mach2) is a very safe insecticide and is very effective against masked chafers and Japanese beetle, however, provides only around 50% of oriental beetle and no control of Asiatic garden beetle. The anthranilic diamide (a new insecticide class) chlorantraniliprole (Acelepryn) just received registration. It is highly effective against all the important white grub species (and a variety of other important turfgrass insect pests), has extremely low toxicity to mammals, birds, fish, and honey bees, is applied at the lowest rate of all white grub insecticides (0.1–0.2 lbs/acre), and seems to be compatible with many predatory and parasitic insects.

Two more recent additions to the arsenal are combination products. Allectus combines imidacloprid with the pyrethroid bifenthrin, and Aloft combines clothianidin with bifenthrin. The idea of these combination products is that they simultaneously provide control of white grubs (through the neonicotinoid compound) and control of surface feeding insects (through bifenthrin). Thus, they are a matter of convenience. From an IPM (intelligent or integrated pest management) standpoint, these combinations are questionable as white grubs and surface feeders rarely cause problems in the same turfgrass area. Unless the latter is the case, combinations only encourage unnecessary insecticide use which increases (1) the chances of insecticide resistance or enhanced microbial degradation and (2) and unnecessarily kills beneficials (higher potential for secondary pest outbreaks). If a turfgrass area has the potential of problems with white grubs and surface feeders, make sure not to apply the combination more than 3–4 weeks before the surface feeders should be controlled to avoid the loss of bifenthrin activity.

Information taken 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.

Greenhouse and Nursery - Pythium on Mums

Pythium is a common root rot of mums grown in pots and in the field. The following is a short article on the subject.

Pythium on mums is a soil-borne disease that thrives under prolonged periods of wetness and high soluble salts. It is known as a water mold. Plants that have experienced stress due to heat or drought are more susceptible to infection. Symptoms of root rot include chlorosis, wilting, and stunting. Roots infected with Pythium appear tan to black and water-soaked. The disease often will progress down rows and expand out from initial wet areas where it started.

Control: Cultural methods include removing infected plants, adjusting watering and fertilization practices, managing fungus gnats, and avoiding the reuse of pots and trays. Overwatering can lead to problems with this diseases. Mums in pots can also be grown off the grown on benches, inverted trays, blocks, or other means to avoid soil contact. Chemical control options include Subdue MAXX, Alliette, Truban, Alude, Terrazole.

Darkened roots from Pythium infection. Photo from Michigan State University Ornamental IPM.

Wilting mum due to pythium. Photo from University of Maryland Ornamental IPM program.

Some information taken from the University of Maryland Ornamental IPM Program newsletter - Greenhouse TPM/IPM Weekly Report, University of Maryland Cooperative Extension.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale V

This is a continuation of the series on plants for Delaware landscapes featuring those that are being offered at the Fall UDBG plant sale.

Anemone virginiana, tall thimbleweed, native, sun to part shade, moist to dry soils, 1-2', tall spikes of white flowers then followed by long lasting thimble-shaped seedheads.

Asclepias purpurascens, purple milkweed, native, sun to part shade, moist to wet soils, 2-3', long blooming intense pink flowers, attractive pods.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale IV

This is a continuation of the series on plants for Delaware landscapes featuring those being offered at the Fall UDBG plant sale.

Rudbeckia laciniata, cutleaf coneflower, native, sun to part shade, moist soils, 3-4', yellow daisy-like flowers, drooping rays & dome-like green disk, butterflies love this flower.

Sedum cauticola 'Mini Ewersii', stonecrop, sun, moist to dry soils, <6", compact blue to reddish leaves; magenta flowers.

Landscape - Storm Damage to Bradford Pear

The following is a picture of a Bradford pear split into two by storm damage that I took recently. Although Bradford pears are a beautiful flowering tree in the spring, this is one of the common problems with this tree and a reason why it is often short lived. It is also considered an invasive plant.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale III

This is a continuation of a series on plants to consider for Delaware landscapes featuring those being offered at the fall UDBG plant sale.

Eupatorium rugosum 'Chocolate', snakeroot, Native, sun to part shade, moist to wet soils, 3-5', chocolate colored leaves, purple stems, bright white flower clusters.

Miscanthus sinensis var. purpurascens, flame grass, sun, moist to dry soils, 4-5', flowers August to frost, brilliant flame-colored foliage with silvery plumes

Turf and Landscape - Cicada Killers

An insect in lawns that often causes concern by homeowners is the cicada killer. The following is come information.

The red and black wasp with yellow bands digging holes and buzzing around lawns is called a cicada killer wasp. Male cicada killers may fly at individuals because they are very territorial, but they cannot sting since they do not have stingers. Females are difficult to provoke, but they can sting. Female cicada killers spend most of their time digging out nests or hunting for cicadas. The entrance to the nest is about ½ an inch in diameter and the wasp kicks sand out of the nest into a Ushaped mound. Female wasps attack cicadas, carry the paralyzed cicada to her nest, and lay an egg on it. The egg hatches and the larva eats the cicada. There is only one generation a year. Control is usually not required unless the insect is a nuisance or is in an inconvenient location. Products labeled for ground insects will help control the wasp; apply the material to the nesting area and then disrupt the soil surface and respray. As females attempt to repair damage to the tunnels they will contact enough chemical and die. Limit traffic around the nest so the application is not disturbed and the wasps will contact the insecticide.

Cicada killer and cicada. Photo by Ronald F. Billings, Texas Forest Service, Bugwood.org.

Information by Brian Kunkel, Ornamental IPM Specialist, UD

Floriculture - Treating Cut Flowers

We have many farm stands and greenhouse growers that put out field grown cut flowers for sales from spring to fall. The following is an article on treating cut flowers to preserve their sales longevity and improve quality.

As more and more growers are expanding their businesses by growing field-grown cut flowers, it is important to understand that all handling, from harvesting to marketing, will significantly affect the quality and the longevity of the flowers. Therefore, growing those beautiful field-grown flowers is only part of what it takes to have a successful cut flower business.

Once harvested from the plant, flowers undergo physiological changes that often lead to an early senescence. Steps to delay the process rely on consideration of many aspects of handling. Factors such as the stage and time of day of harvesting, bunching, sleeving, boxing (if necessary), temperature treatment, and the holding solution will all influence the quality and longevity of the flowers. In this article, I will discuss how sugars affect the postharvest quality of cut flowers and what a grower can do to optimize their postharvest performance.

It has long been known to the cut flower industry that flowers produced in the greenhouse during winter, when the natural light intensity is low and the days are short, are often of lower quality than those produced at other times of the year. In the Northeast region, the postharvest quality of many field-grown cut flowers declines in the fall season as the temperatures drop and the number of hours for photosynthetic activities is reduced. Providing external sugar to flowers harvested during fall is therefore more crucial than to those harvested in the summer. However, placing all field-grown cut flowers in a preservative solution will extend their postharvest life and keep their quality.

Many flowers are harvested before they are fully developed, to ensure a long postharvest life and to minimize mechanical damages that might occur during handling. The development of these flower buds requires food (carbohydrates), which is stored in the leaves and stems. These stored carbohydrates can be mobilized for the flower bud to use but may be insufficient when the buds are harvested at a tight-bud stage. The maintenance of the metabolic activities, including respiration, even for flowers that are harvested when fully developed, requires that adequate reserves are provided in order to achieve a reasonable postharvest life. When the stored carbohydrates are low, leaves and flowers senesce rapidly and petals that develop at low sugar levels have pale colors. Under these situations, supplements can be provided to the flowers by adding table sugar (sucrose) to the vase solutions. However, it is important to remember that a sugar solution is also perfect for the growth of microorganisms, so that a biocide should be added to the vase solution as well (see below).

External sugars can be provided to cut flowers by dissolving a known amount of sugar, along with a biocide, into the vase solution. The optimum concentration of sugar varies significantly depending on the flowers being treated. Most flowers benefit from a continuous supply of 2% sugar in the vase solution. Some flowers, such as Gladioli, have been shown to benefit from higher concentrations, such as a 4 to 6 % sugar solution. Other flowers, such as Zinnias and Coralbells, sustain damage when treated with concentrations of sugars higher than 1%. Still others, such as Chrysanthemums and China Asters, do well without any sugar in the keeping solution. Therefore, it is important that before treating the entire batch of flowers, a small-scale experiment be conducted. A close approximation of a 1% sugar solution can be obtained by dissolving 2 level teaspoons of sugar into a quart of water. (To be accurate, dissolve 10 grams of sugar and bring up to a 1-liter solution with water.) To that, add a biocide to inhibit the growth of microorganisms.

Two common biocides are household bleach and Physan,which is used as a disinfectant in restaurants. A solution of 50 ppm bleach or 100 ppm of Physan works well for most cut flowers. To obtain a 50 ppm bleach solution, add 1 ml of bleach to a liter (quart) of solution and to obtain 100 ppm Physan, add 0.5 ml of Physan to a 1-liter solution. (For measurement of very small quantities, a medicine-dropper is useful. This can be obtained from a pharmacy, and usually contains .8 or 1.0 ml, so that one dropper of bleach or approximately half a dropper of Physan per quart or liter will give approximately the desired ppm.) Keep in mind that after a while bleach breaks down and freshly made solutions should be used each day. Both biocides can also cause stem discoloration in some flowers, so pre-testing on a small number is essential.

Another method of providing sugars is to 'load' the stems and leaves with high concentrations of sugars for a short period of time, typically overnight. This practice is referred to as a 'pulse' treatment. The treatment presumably allows accumulation of adequate sugar in the leaves and stem during that time period to aid the development of flowers. A classic example is to pulse Gladiolus stems with a 20% sugar solution before marketing. When Gladioli are pulsed overnight, flowers opening farther up the spike and are larger and the entire stem has a longer vase life. Although pulse treatment works well with some cut flowers, it does not always work with others. In some cases, the stems cannot absorb enough carbohydrate during that short treatment time, so the benefits of a pulse treatment will not be detected.

One key ingredient in a preservative solution that is critical for the handling of field-grown cut flowers is citric acid, which is used to lower the pH. It has been shown that low pH water (pH=3.5) travels faster in the water-conducting system (xylem), thereby preventing or reducing wilting that frequently occurs in field-grown flowers. Commercial rehydration solutions (such as Hydraflor) often contain sufficient citric acid to lower the pH of the solution to 3.5. However, if flowers are showing signs of wilting after harvest, they should be placed in a solution containing only citric acid (no sugars) and be left overnight in a cool location with subdued light, before transferring them to a preservative solution containing sugar. Citric Acid may be ordered from most pharmacies, and currently costs about $8 per pound. For most water (depending on the quality of water), 350 to 500 ppm citric acid is adequate. Unfortunately it is difficult to translate this into teaspoons of citric acid per volume of water, because the size of the crystals (and therefore weight per teaspoonful) may vary from one manufacturer to another. If a gram scale is available, the most accurate way to obtain the solution is to measure the citric acid by weight. (Between 0.35 grams and 0.5 grams of citric acid will make a liter -- approx. 1 quart-- of 350 to 500 ppm solution.) Another method would be to use a pH indicator paper or a pH ‘pen' (available through a greenhouse supplier) to find out the adequate amount of citric acid to mix into the solution. (Keep adding citric acid until the pH of the solution is lowered to 3.5.)

In addition, you may want to give your customers a simple recipe for a preservative solution so that their flowers will have a better postharvest quality. The first formula calls for mixing a can of a non-diet citrus soda with 3 cans of water and 1.2 ml of household bleach (contents of 1 to 1 ½ droppers). The second formula calls for 2 tablespoons of fresh lime or lemon juice, 1 tablespoon of sugar, 1/2 tablespoon of bleach and 1 quart of water. Mix the ingredients and the solution is ready for the cut flowers. These solutions contain the major active ingredients necessary for a good preservative solution, i.e. sugar, citric acid, and a biocide. Because these solutions contain bleach, they need to be replaced every day, or at least every other day, to prevent the growth of microorganisms.

Reprinted from "Sugar and Acidity in Preservative Solutions for Field-Grown Cut Flowers" by Dr. Susan S. Han, Plant and Soil SciencesUniversity of Massachusetts, Amherst. Go to http://www.umass.edu/umext/floriculture/fact_sheets/specific_crops/presvcut.html for more information.

Business - Some Keys to Profitability I

This is the first in a series on some keys to profitability for landscape and turf management businesses. This first installment focuses on knowing operational costs.

By knowing and evaluating costs associated with operating your business, you can determine those areas that are eating into profits. Key operational indicators are:

1. The ratio of applied/unapplied labor. In your business, the more labor that can be charged directly to a job, the more potential there is for profit. Labor activities such as cleaning up your shop or yard area, handling and maintaining inventory, maintenance, and trips to get supplies, while necessary (especially maintenance), cannot be recovered directly from a specific job and must be recovered in overhead. Overhead costs are often much harder to determine and may not get charged properly. In addition, the amount of time spent on a specific job in the actual work associated with the job rather than travel, organization, getting started, and ending a work day goes to the efficiency of your work crews. Another point is how efficient is your labor force in getting a job done. Do you have too many or too few employees for a given job? Too many leads to a lot of down time and standing around waiting to do something, too little will over-stress crews and often leads to jobs taking longer than desired thus reducing profits.
2. Applied materials and material variance. Being able to track all materials that go into a job and charge those to a job is critical. One of the killers to profit is waste - using too much materials (such as mulch), throwing away excessive materials, or having a lot pieces or remnants that cannot be used elsewhere or must be reinventoried would be examples.
3. Straight time to overtime ratio. Overtime, while sometimes necessary, should be a rare occurrence. If you are paying a lot of overtime, you need to hire additional employees that can be paid straight time. Excessive overtime eats into profits.
4. Revenue per production employee. This is a measure of just how efficient you business is. If revenue per employee is low, you have too many employees, you have too much inefficiency in your work and jobs, or you have employees that aren't pulling their weight.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape and Turf - Proper Irrigation

With the hot, dry weather, irrigation systems are being used in landscapes throughout the state. The following is an article on factors to consider to reduce water waste and irrigate plants properly.

Improper irrigation can lead to wasted water and potential plant problems with over or under watering. Take time to inspect irrigation systems for broken heads, leaks, clogged drip emitters, obstructed sprinklers, and sprinklers that are malfunctioning. Make sure that sprinklers in turf areas have head to head coverage/proper overlaps. Replace or repair malfunctioning sprinklers with the same types that have the same application characteristics. Don’t put different types of sprinklers in the same zone. Operate at the pressure levels sprinklers or emitters were designed for. Excessive pressure will cause misapplication and potential water waste due to misting or pressure induced leaks; low pressure will lead to poor coverage. Avoid daily watering. Water 1 to 3 times a week to wet the root zone thoroughly but without drainage loss. Cut grass on the high side and maintain mulch layers to reduce surface evaporation losses. Do not water in the middle of the day – night and early morning applications will conserve water. Avoid overspray onto impervious surfaces such as sidewalks or roads and onto areas without plants such as fence lines and pathways as this wastes water. Use a soil probe to check irrigation depth and alter irrigation timings if too shallow or deep. Avoid over-irrigation of landscape beds with overspray from turf areas - landscape beds should be irrigated separately.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape and Turf - Avoid Irrigation Overspray

Irrigation systems are being used daily with the hot, dry weather. One concern is irrigation overspray. Irrigation overspray is a waste of water resources and contributes to runoff. Turf and landscape managers should make efforts to design and operate irrigation systems to avoid overspray. The following is an article on the subject.

Irrigation overspray damages pavement, contributes to stormwater pollution, and is an unsightly waste of a valuable resource. It is called nuisance water and it can be prevented.

Nuisance water is chronic running water in gutters and street crossings, standing water where it doesn’t belong, wet areas that never dry and is a common eyesore. The vast majority of nuisance water could be eliminated if managers would follow proper watering schedules, adjust sprinkler timers, and maintain irrigation systems. Overspray is a major culprit. Overspray is water from a sprinkler that lands outside the planted area on a sidewalk or roadway. This is caused by poor sprinkler maintenance and/or design.

Another common cause of nuisance water, although less easy to remedy, is poor landscape design, such as grass planted on a sloping bank along the roadway.

To locate possible nuisance water, look for runoff from an irrigated area when the sprinklers are on. This indicates that all the water is not entering the soil and could be a sign of overwatering, a malfunctioning sprinkler, a broken waterline, or improper landscape design. If the problem is not remedied, sidewalks, gutters, and streets can become slippery with algae. It can also lead to deterioration of asphalt pavement and can contribute to the creation of potholes in the street.

Irrigation overspray also contributes to stormwater pollution by causing fertilizers applied to the landscape areas to be washed away and flow into the gutter. This enters our storm drain system and eventually flows our waters (bays) which can result in reduced water quality. If you are responsible for the maintenance of landscape or turf areas, inspect your irrigation system to ensure that it is operating properly.

Adapted from information from the City of Cypress, CA.

Pictures from the Delaware State Fair

Some horticultural related pictures from the Delaware State Fair.

Cut flower displays in the Flower Department.

Hanging basket display in the Flower Department.

Maggie Moor-Orth, Master Gardener Coordinator for Kent and Sussex County with Delaware State University volunteering at the Grange Food Area.

UD/DSU Extension Tent with mixed flower containers provided by Lakeside Greenhouses.

Photos by Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape and Nursery - Twig Girdlers

You may see trees and shrubs that have fallen twigs on the ground starting in August. The culprit is the twig girdler. The following is an article on the subject.

Twig girdlers are gray-brown wood boring beetles with a pair of antennae that are about as long as their ¾ inch long bodies. They are active from mid-August into early October when the female lays her eggs. Twig girdlers can be responsible for hanging or fallen twigs on or around a variety of trees including hackberry poplar, linden, redbud, dogwood, and various fruit and nut trees. Heavy infestations can disfigure landscape trees.

The female twig girdler begins the process by chewing a deep V-shaped groove around a small twig and laying an egg in the twig beyond the cut. The girdled portion of the twig that contains the egg will soon fall to the ground. It can be recognized by a smooth cut on the outside of the twig near the bark and a ragged center where the twig breaks. The larva will tunnel into the dead twig and feed until winter. Development will resume in the spring. Ultimately, the larva will pupate in the twig and emerge as an adult late in the summer.

Fallen twigs contain the larvae of this insect so they should be collected and destroyed as soon as practical but before early May of the following year. Hanging twigs should be pruned out and destroyed if practical. An application of Sevin at the first sign of girdling, and repeated twice at two-week intervals, may reduce damage to infested trees. The insecticide kills the adult females before they can lay eggs but will not penetrate the twigs to kill deposited eggs or live larvae.

Several closely related species of beetles damage twigs in a similar manner but are less common. This includes mulberry bark borers, oak stem borers, spined bark borer, and the mulberry borer. These may all cause the same damage as the twig pruner and girdler.

Twig Girdler. Photo from Virginia Tech.

Information taken from "TWIG GIRDLERS" By Lee Townsend in the July 24, 2006 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture and from a fact sheet from Virginia Tech on twig girdlers.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale 2

This is a continuation of the series on plants for Delaware landscapes featuring those being offered at the fall UDBG plant sale.

Dryopteris marginalis, eastern wood fern, native, shade to part shade, 12-15", evergreen leathery leaves, tolerates dry shade once established.

Solidago rugosa 'Fireworks', goldenrod, native, sun to part shade, 3-4', arching spires of brilliant yellow flowers attractive to butterflies.

Greenhouse - Time to Clean Out Houses

Summer sales are ending and poinsettia season has not started. Now is the time to perform maintenance in empty greenhouses. The following are some maintenance actions to consider:

• Remove all plant materials, do not keep a few plants in an otherwise empty house
• Remove all weeds before they go to seed.
• By shutting down fans for a few days, you can solarize a house and kill many insects and other pests. Be carefull that you do not damage any materials that could melt with the high temperatures.
• If houses are completely empty, you can spray existing weeds with glyphosate. However, be careful that no material is vented out where it can affect plants growing outside or can be drawn into other houses. It is best to shut off fans and spray in early morning.
• Repair or replace landscape fabric on floors.
• Spray all bench surfaces with disinfectants.
• Replace greenhouse plastic film if needed.
• Have heaters serviced before the fall heating season.
• Do any necessary painting, replace any insulation as necessary
• Check all irrigation systems for leaks and make repairs

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Nursery - Lime and Nursery Growing Media

I came across a good article on lime in potting media from Andrew Ristvey from the University of Maryland that I thought I would share.

Questions about liming potting medium have come up recently. This is an important issue that needs to be addressed in your nursery if you are creating your own mix. Your potting soil or substrate is not really a true soil and apart from sharing a few physical traits like providing a place for roots to grow, there is very little chemically and physically that they have in common. I have always written about the importance of monitoring your substrate for electrical conductivity and pH. But what should you be doing about pH before you place your plant in the container? This is a complicated answer. Most important is that you have a goal for what ever plants you are growing. It is often recommended that your substrate have a pH of between 5.5 and 6.2. Why so low? Without getting too complicated, the organic materials you use to make your substrate are chemically different than a mineral soil. Your plants will rely on you supplying most if not all of the 14 essential mineral nutrients so not to limit growth. The availability of many of these nutrients is determined by the pH of the substrate. The recommended pH optimizes nutrient availability. Too high a pH and nutrients like iron and manganese are not available to the roots, causing a deficiency. Too low a pH and the same nutrients can become too available, causing toxicities or preventing the uptake of other nutrients.

Adjusting the pH of your home-made substrate before planting may or may not be necessary. The most commonly used substrate amendment apart from fertilizer is lime. Lime adds calcium carbonate and dolomitic lime adds a little magnesium with that calcium to your substrate. Apart from supplying calcium and magnesium to your plants, lime can increase the pH of your substrate and most importantly will act as a buffer, reducing the potential for large pH swings. Various recommendations have been cited by those who add lime to their homemade mix, but without knowing the whole story about your nursery, a blanket recommendation is hazardous at best. First and foremost, your irrigation water must be tested to determine the alkalinity or the amount of bicarbonates and carbonates. Without this information first, no recommendation should be made. A good level is between 50 and 80 ppm (1 ppm = 1 mg/l) with a little room for play. If your irrigation water has alkalinity of 120 ppm or greater, I would not recommend the use of lime in your substrate or I would be very sparing. However if your alkalinity is much below 50, then there are other factors to consider, like what type of fertilizer you are using, what plants you are growing, and what materials you are mixing for your substrate. Pine bark usually is relatively acidic, and the fresher it is the more acidic it is. Try to insist on a well aged or composted pine bark from you supplier, when the pH will have stabilized.

Interestingly, most of the recent research has shown that liming substrates decreases growth compared to adding just micronutrients or that adding more than 5 lbs of lime per yard of substrate reduces plant growth. Another recent recommendation is the type of particle size you use. Recent studies have shown that a long lasting granular lime is better than pulverized lime (which does not last long in your container). In one study, 5 lbs per yard of granular lime had the best affect on growth of juniper compared to pulverized lime, if lime was used. However in the same study, no lime addition also proved as effective as 5 lbs of granular per yard. Still other researchers are not convinced of the effectiveness of lime. In my opinion, each nursery will need their own recommendations based on the factors listed above. Your experience is the most valuable information you can use to determine the best course of action. If you are not having pH problems, then don’t fix anything. However, if you are, then you must gather all the facts to determine your liming rates. I would recommend the use of granular lime (solely or mixed with pulverized) to give persistent and steady pH balance, but be careful of over-applying. You can contact me for more information on your situation.

Reprinted from "pH and Potting Media" by Andrew Ristvey in the July 18, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Landscape - Decay in Trees

I came across a good article on decay in trees and thought I would share it with you.

Living landscape trees are subject to internal decays of branches and trunk and of buttresses and roots. Decay in living trees appears as a softening or weakening of the woody xylem tissues of the sapwood and the heartwood. These decays are caused by fungi that can decompose the structural material of the tree.

Disease progress. The disease begins when a windblown spore of a wood-decay fungus comes in contact with a tree wound and, given the right conditions (possibly involving other non-decaying microorganisms), germinates. Wounds such as those caused by lawn equipment, construction activity, pruning, or wind and ice damage are typical locations for this activity. The germinating spore produces a germ tube and then branched hyphae and mycelia which invade fiber, vessel, tracheid, and ray cells of the wood. Wood often becomes discolored. The fungal hyphae release enzymes that break down cellulose (brown rot) or cellulose and lignin (white rot), thus providing food for the fungus and loss of rigidity for the tree. Parts of the tree may break and fall, or the tree may topple over if roots are decayed. The fungus reproduces by forming a mushroom, conk, or shelf-like structure (fruiting structure in which spores are formed) directly on the limbs, trunk, butt, root flares or on roots at some distance from the base of the tree.

However, trees are not passive victims; they respond to wounding and fungal invasion. When an injury occurs, the invading wood-decay fungi encounter tree defense mechanisms. The vertical movement of the decay fungus is impeded by plugging of xylem tracheids and vessels with resins and tyloses above and below the wound. Horizontal movement of fungi is impeded in an inward direction by the already existing growth rings and in a radial direction by toxic substances produced by the ray cells. Decay is prevented from moving outward to new growth by barriers laid down by the vascular cambium after injury occurs. Of these various defenses the strongest is that formed by the new growth. Consequently, decay will not proceed into subsequent yearly growth increments unless they are re-injured.

In circumstances where wounding is minimal and the tree is quick to respond to wounding and invasion, the tree suffers some internal discoloration and little or no decay, thus retaining its structural integrity. However, where wounding is extensive and when the tree is not capable of producing a quick, effective response, the decay fungus spreads and the tree is weakened.

Wood decay fungi are usually identified by their conks. The conks of some of the common wood decay fungi important to tree health are described here. The first four listed have slits, or gills on the underside of the conk or mushroom cap, and the others have pores on the conk underside. Several of them are characterized as having a broad host range and can attack many species while other decay fungi are specialized, attacking just one or a few tree species.

Armillaria mellea, the shoe string root rot or oak root rot fungus has a wide host range including conifers and hardwoods and is very important in shade tree pathology. White patches of mycelium and shoestring-like rhizomorphs of the Armillaria fungus can be found under the bark of infected trees. Clusters of gilled, tan-colored mushrooms may develop at the base of infected trees.

Flammulina velutipes (Collybia velutipes) annually produces clusters of mushrooms with stout stalks and moist, smooth reddish orange to reddish brown caps. The cap has white gills and is one to three inches across and the dark, hairy stalk is one to three inches long. This fungus produces white rot of a wide range of tree species.

Pleurotus ostraetus, the oyster mushroom, causes a white rot of the heartwood and sapwood of many landscape trees. The fungus produces an off-white fleshy shelf-like mushroom up to eight inches across. The mushroom may have a short stout stalk and the underside of the conk has gills.

Schizophyllum commune annually forms clusters of small, leathery gray fan-shaped conks one or two inches across. The gilled cap of this fungus is attached directly to the tree without a stalk. The fungus causes white rot on a wide range of declining and dead trees.

Fomes fomentarius produces gray, woody, perennial hoof-like fruiting conks. The conks have pores on their underside and may be eight inches wide and several inches thick. The fungus causes white rot on a wide range of trees.

Ganoderma applanatum (Fomes applanatus) forms a thin shelf-like gray-brown conk up to one foot across. The underside of the conk consists of minute white pores and the surface turns brown when bruised or scratched - giving it the name artists' conk. This fungus causes a white rot of a broad range of tree species.

Ganoderma lucidum also produces a large conk, usually at the base of the infected tree. The upper surface has a reddish-brown smooth varnish-like appearance while the undersurface with pores is white to tan. This fungus also has a wide host range.

Inonotus dryadeus (Polyporus dryadeus) causes a root and butt rot particularly on oaks. The decay begins on the root system and the fungus eventually reaches the butt of the tree where it forms large, tough, irregularly shaped gray to brown brown shelves with pores at or just above the soil line. With age, they become rough and dark brown.

Laetiporus sulphureus, (Polyporus sulphureus) also called the sulfur fungus causes brown rot of the butt and heartwood of living and dead trees. This fungus produces clusters of annual bright yellow or yellow-orange conks up to a foot across. The undersides of the conks are covered with minute pores. It has a wide host range.

Phellinus robineae (Fomes rimosus), a pathogen of black locust, produces yellowish brown to gray conks with a brown pore-bearing surface. The conks are several inches to a foot across and protrude shelf-like away from the trunk of affected trees.

Stereum gausapatum, a major oak pathogen, and other related Stereum species cause white rot of many different trees. Conks appear as clusters of thin, brownish, shelf-like structures a little more than two inches across. Injured conks may leak a red fluid.

Trametes versicolor (Coriolus versicolor, Polyporus versicolor) fruiting bodies annually form dense overlapping clusters on decaying branches and trunks. The caps, one to two inches across, are leathery and colorfully arrayed with zones of white, yellow, red, brown, gray, green and bluish green. Tiny white pores can be found on the cap underside. Generally causing white rot on stressed trees, it can in some circumstances cause heart rot of wounded, but not otherwise stressed trees.

Trametes hirsuta (Coriolus hirsutus, Polyporus hirsutus), somewhat larger than T. versicolor, produces leathery gray to brownish caps without zones. This fungus also causes a white rot of many tree species.

Reprinted from "SOME OF THE CAUSES OF DECAY IN TREES" By John Hartman in the August 13, 2007 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.

Turf - Proper Irrigation

Hot, dry weather is upon us. For those property owners with lawns receiving irrigation, it is important to know how to irrigate properly. Turf and landscape professionals installing irrigation systems should take time to educate their clients on proper irrigation. The following is and article on the subject.

Water is essential for turf growth. It is required for germination, photosynthesis and as a part of the turf. Most of the water absorbed by turf is transpired through the leaves into the atmosphere. This water moves nutrients from the soil into the plant, but equally important, it eliminates heat buildup from solar radiation.

The water applied by an irrigation system will evaporate from the soil and be transpired from plant surfaces. Evaporation and transpiration (evapotranspiration) depend mostly on the climate around the plant, thus, the amount of water used by turf changes with the seasons. Because of this, for a well-managed turf, irrigation frequency should change with the time of year.

Only water that is in contact with the roots can be absorbed by the plant. The volume of soil where water can be stored is as deep as the roots are. Root depth is affected by mowing, fertilizing and irrigation practices. A well-managed turf system will develop most of its roots in the first 12 inches of the soil. Another important property of the soil reservoir is that soils have a limited ability to store water. The larger the pores in the soil the less water the soil will hold. Sandy soil hold much less water than loam soils.

Two questions must be answered when scheduling irrigation:

WHEN DO I IRRIGATE?

Water should be applied to turf only when soil-water in the root system has been depleted to an unacceptable level, usually by 1/2 to 2/3 of the stored soil-water. There are several ways to determine when the soil-water reservoir has been depleted beyond an acceptable level. These are:

Visual inspection of the turf . Becoming familiar with the way that turf reacts when water is becoming scarce in the soil is a common method of deciding when to apply irrigation. Common symptoms of water stress include leaf color changes to a bluish-gray tint, footprints that linger long after being made, and curled or folded leaf blades.

Estimations based on climatic records . Past history of climate can be used to estimate how often irrigation should be applied to turf. Tables are available that show the expected number of days that soil water will last for a certain texture of soil.

Direct measurement of soil moisture . Using sensors for measuring the amount of available water in the soil is another way to determine when to irrigate. One such sensor is the tensiometer. As the soil dries, water moves out of the tensiometer through the ceramic, causing a suction that is measured by the vacuum guage. Other moisture sensors are also available and systems can be automated using these sensors.

HOW MUCH WATER SHOULD I APPLY?

The quantity of water applied to turf should not exceed the amount required to refill the soil occupied by the root system (poor quality water may require higher volumes for leaching). Regardless of the time of year, for an established turf the quantity of water applied at each irrigation should always be the same. Irrigation will not be required as often during low demand periods. Typical Delaware soils will be able to hold at least 1 inch of water per foot of soil. The amount of water to apply to a one-foot-deep soil water reservoir, which has been depleted to 50 percent and has a water holding capacity of one inch per foot (1"/ft), is 2/3 of an inch of water.
This assumes an irrigation efficiency of 75 percent. The total volume required will depend on the size of the area being irrigated and the soil-water holding capacity. It takes 620 gallons of water to apply one inch of water to 1000 square feet of an area.

APPLYING IRRIGATION

In order for irrigation to be successful and efficient, the volume of water applied must be measured. There are several ways to measure irrigation volumes of water.

Using a water meter . In a permanently installed system a water meter should be included as part of the irrigation system. In systems that are connected to an urban water supply, the meter installed by the service company can be used. The time required to apply the necessary water can be easily determined by observing the water meter to measure how much water is applied by the irrigation system in a minute. For example, a system that requires 1200 gallons is turned on, and from the meter it is observed that 12 gallons per minute are being used. Thus, the time that the irrigation system should be turned on is 100 minutes (1200 gallons divided by 12 gallons per minute).

Measuring the depth of water applied . When a water meter is not available place five wide- mouth, flat-bottom cans spaced equally along the diagonal of four sprinklers. After 20 minutes of irrigation, turn the system off and use a ruler to measure how deep the water is in each can. Average the five measurements and use the average to determine the time required to apply 2/3 of an inch of water. For example, if a 20-minute can test resulted in an average water depth of 1/2 of an inch, the time that irrigation system should be turned on in order to apply 2/3 of an inch of water is obtained from is 27 minutes. Any water applied after 27 minutes will be wasted as deep percolation.

If a hose and sprinkler is used with this method, set the sprinkler pattern to 1/4 of a circle before carrying out the test. Move the sprinkler to each corner of the irrigated area and irrigate for five minutes from each corner for a total of 20 minutes. When irrigating the turf, apply water for the irrigation duration when the hose-and-sprinkler is used in full circle; for 1/2 the irrigation duration when the hose-and-sprinkler is used in half circle; and for 1/4 the irrigation duration when the hose- and-sprinkler is used in quarter circle. Also, if possible, carry out the test in the early morning hours and under no-wind conditions.

Using automatic shut-off values . A variety of automatic shut-off valves are available that are especially suited for irrigating with a hose and sprinkler. These allow the user to set a time period or volume to apply. These are inexpensive and convenient and reduce water waste due to lack of attention to hose-and-sprinkler systems.

Using soil-moisture sensors . When permanently installed irrigation systems are run using timers, sensors can be used to control these systems. The timer should be set to irrigate every day to apply about 1/3-1/2 of an inch of water during early morning hours for best efficiency. The moisture sensor will allow irrigation only if water is required.

Adapted from "Turf Irrigation for the Home" by F.S. Zazueta, A. Brockway, L. Landrum and B. McCarty, University of Florida.

Plants to Consider for Delaware Landscapes - Offered in the Fall UDBG Plant Sale

This is the first in a series of plants for Delaware landscapes featuring those being offered at the Fall UDBG plant sale.

Indigofera pseudotinctoria 'Rose Carpet', rose carpet indigo.

'Rose Carpet' is a dense, low-growing shrub or subshrub, 8-12" tall, 2-4' wide. Has dense rose colored, pea-like flowers which bloom heavily in June and July and sometimes continue intermittently to September.



Boehmeria platanifolia, false nettle, A non-stinging nettle; sun to part shade, 3-4' high, deeply incised leaves, very ornamental.

Turf - Fall armyworms

Fall armyworm season will be coming in August. These pests can sometimes attack turf. The following is an article on fall armyworms.

Fall armyworm caterpillars, sometimes known for marching in large "armies", are potential turf pests in late summer and fall. Consuming all green above-ground plant parts, they are capable of killing or severely retarding the growth of grasses. During most seasons, parasitic enemies keep fall armyworm larvae down to moderate numbers. Cold, wet springs seem to reduce the effectiveness of these parasites and allow large fall armyworm populations to develop. Conversely, years such as 2002 with mild winters and dry summer allowed early and sustained periods of infestation.

The fall armyworm has a wide host range but prefers plants in the grass family. Most grasses, including Bermudagrass, fescue, ryegrass, bluegrass, Johnsongrass, timothy, corn, sorghum, Sudangrass, and small grain crops, are subject to infestation.

Biology

The mature green, brown, or black larva, 35 to 50 mm long, has a dark head usually marked with a pale, and a distinct, inverted "Y". Along each side of its body is a longitudinal, black stripe. There are four black dots on the dorsal side of each abdominal segment.

The moth has a wingspan about 38.5 mm. The hind wings are white and the front wings are dark gray, mottled with lighter and darker splotches. Each forewing has a noticeable whitish spot near the extreme tip. The minute light gray eggs are laid in clusters on any vegetation (shrubs and posts included) and are covered with grayish, fuzzy scales from the body of the female moth. The eggs become very dark just before hatching. The pupa, approximately 30 mm long, is originally reddish-brown and darkens to black as it matures.

Fall armyworms probably overwinter as pupae in the Gulf Coast region of this country. Egg-laying moths migrate northward throughout the spring and summer and arrive in Delaware during August. New moths may continue to appear into October. Each female lays about 1,000 eggs in masses of 50 to several hundred. Two to 10 days later the small larvae emerge, feed gregariously on the remains of the egg mass, then scatter in search of food. Unlike the nocturnal true armyworms, fall armyworms feed any time of the day or night, but are most active early in the morning or late in the evening. When abundant, these caterpillars eat all the food at hand and then crawl in great armies to adjoining fields. After feeding for 2 to 3 weeks, the larvae dig about 20 mm into the ground to pupate. Within 2 weeks, a new population of moths emerges and usually flies several miles before laying eggs. Several generations occur each year in Delaware. Newly installed sod is more attractive to FAW and more susceptible to damage. Turf symptoms can first appear on lawn edges, and around areas near lights.

Control

The fall armyworm is more difficult to control chemically than the true armyworm. Control of fall armyworms will be improved if you cut the turf prior to treating. A light irrigation prior to treatment may also help as will treating late in the day. Large fall armyworms are difficult to control. Don't expect 90% control. Pyrethroids will do a reasonable job as will Sevin (carbaryl) and even Orthene (acephate) against small worms. For professionals, products like Mach 2 and Scimitar will also control turf feeding caterpillars, but don't expect miracles, especially if they are allowed to feed and grow for a week or more before treating. In warm weather the caterpillar can go from egg to pupa in 2 weeks. If the worms are very large (inch and a half long) then they will go into the soil very soon to pupate and control efforts may be a ineffective. Timing is important and a repeat application may be necessary in some situations. On a lawn, threshold is about one larva per square foot of turf. Soap disclosure solutions can be helpful for determining larval infestations.

Information from North Carolina State University.

Landscape - Millipedes

Homeowners often are concerned when they see millipedes coming into their house and landscape professionals may be called upon to deal with millipedes in a landscape. The following is information on millipedes.

Millipedes are long, many segmented creatures that use their two pairs of legs per body segment to move with deliberate determination. There are several species in Delaware so we can see a variety of shapes and colors. Millipedes can be very abundant in forest litter, grass, thatch, and in mulched areas. These places provide them with the food and dampness that they prefer. Usually, millipedes stay out of sight unless abundant rainfall or some other event, such as the mating season, puts them on the move.

While harmless and in fact, helpful recyclers, millipedes generally are not welcomed with enthusiasm. They often invade crawl spaces, damp basements and first floors of houses at ground level. Common points of entry include door thresholds (especially at the base of sliding glass doors), expansion joints, and through the voids of concrete block walls. Frequent sightings of these pests indoors usually mean that there are large numbers breeding on the outside in the lawn, or beneath mulch, leaf litter or debris close to the foundation. Because of their moisture requirement, they do not survive indoors more than a few days unless there are very moist or damp conditions.

MILLIPEDE MANAGEMENT

Minimize moisture & remove hiding places - The most effective, long-term measure for reducing entry of millipedes (and many other pests) is to minimize moisture and hiding places, especially near the foundation. Leaves, grass clippings, heavy accumulations of mulch, boards, stones, boxes, and similar items laying on the ground beside the foundation should be removed, since these often attract and harbor pests. Items that cannot be removed should be elevated off the ground.

Seal cracks and openings in the outside foundation wall, and around the bottoms of doors and basement windows. Install tight-fitting door sweeps or thresholds at the base of all exterior entry doors, and apply caulk along the bottom outside edge and sides of door thresholds. Seal expansion joints where outdoor patios, sunrooms and sidewalks abut the foundation. Expansion joints and gaps should also be scaled along the bottom of basement walls on the interior to reduce entry of pests and moisture from outdoors.

Exterior applications, in the form of barrier sprays, may help to reduce inward invasion when applied outdoors, along the bottom of exterior doors, around crawl space entrances, foundation vents and utility openings, and up underneath siding. It also may be useful to treat along the ground beside the foundation in mulch and ornamental plant beds, and a few feet up the base of the foundation wall. Heavy accumulations of mulch and leaf litter should first be raked back to expose pest hiding areas. Insecticide treatment may also be warranted along the interior foundation walls of damp crawl spaces and unfinished basements. There is no benefit from treating indoors. Millipedes that do get inside will not find what they need to survive.

Reprinted from "MILLIPEDES ON THE MOVE" By Lee Townsend and Mike Potter in the July 14, 2008 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.

Landscape and Nursery - Plants for Delaware Landscapes: Chastetree

The following is a continuation of the series on plants adapted to Delaware landscapes.

Vitex negundo, Chastetree, is a small tree with palmately compound leaves that are medium green and slightly gray on the underside. The plant can grow from 3 to 15 feet depending on the microclimate. Listed by Dirr as a zone 6 plant, it thrives in zone 7 and 8. The tree has an open airy vase shape that will need to be pruned every few years to encourage new growth. Like many flowering trees, chastetree does best in full sun with slightly acid soils. Once established, chastetree can tolerate some drought and some salt conditions as well. Chastetree blooms beautifully in early summer when very few trees are in bloom and becomes covered with blue or lavender flower spikes that are fragrant. Despite all the flowers, chastetree is considered allergy free and, like many flowering plants, is a butterfly magnate. There are no insect pests, but a leaf spot disease can defoliate the tree and wet soils will cause a root rot.


Information and photo from Ginny Rosenkranz, Extension Educator, Wicomico/Worcester/Somerset Counties, University of Maryland in the July 11, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Landscape - Decaying Trees are Hazards

Decay in living trees can weaken their structure and create a situation where injury to people or damage to property could result from falling limbs, trunk breakage, or tree toppling. The following is information on this subject from the University of Kentucky.

A tree normally would not present a hazard in the landscape unless there is a potential target for it to fall on. After all, a falling tree in the middle of a forest is not the hazard that a similar tree would be in a school playground. County Extension Agents, arborists, landscapers, and grounds maintenance personnel should recognize how tree decay disease can create a real hazard in the landscape.

Trees that represent a hazard can often be recognized by evidence or indicators of decay disease or tree structural weaknesses. Some of these will be listed here. An actual evaluation of hazard trees is best done by a professional certified arborist. Knowing that some of these indicators are present should give the tree owner reason to contact a certified arborist.

Visible external evidence. The following is a partial list of tree hazard indicators which, if present, are cause for concern and a stimulus to look more closely at the problem to determine if a hazard really exists.

Tree branch and foliage appearance (indicating a root or lower trunk problem): diminished size, frequency, and health of buds; decreased annual twig growth; reduced canopies; unsatisfactory size, density, and color of foliage; epicormic growth; deadwood and dieback in the crown.

Tree structure: poor crown balance; multiple branch attachments; narrow crotch angles between trunks or between branches and trunk, especially with included bark; long slender non-tapering branches; abnormal crooks in branches; and leaning trees.

Tree diseases and defects: canker diseases; trunk and branch cracks, splits, and bulges; dead bark; bark texture changes; weeping wounds; cavities and hollows; topped trees; branch stubs; flush cuts; dead wood and broken, hanging branches; root decay; deep stem fluting; lack of basal flare; and girdling roots.

Biological indicators: fruiting bodies of decay fungi on buttress roots, trunk, or limbs; fungal mycelial mats or fans; fungal rhizomorphs; insect emergence holes; insect frass; bird or mammal nesting holes; and bee colonies inside the tree.

Site factors: nearby building construction; trenching through the root zone; changes in water drainage patterns; soil compaction; clearing of a densely wooded site leaving remaining trees exposed to wind; soil erosion; changes in grade such as cuts and fills; extremely light soils providing poor root anchorage.

Buried evidence. Less accessible, but very important to tree hazard determination is the partially buried area at the base of the trunk which includes the buttress or flare roots. The root flare area may need to be carefully excavated to reveal decay, fungal mycelium and rhizomorphs, dead bark, injuries, cracks, and other tree defects. For a tree to be safe and healthy, it is necessary for most of the lower trunk and buttress roots to be free from injury and disease.

Evidence inside the tree. Decay of the wood inside the tree can often be foretold by visual evidence such as fungal fruiting bodies, hollows, and cracks. Nevertheless, to survive, grow, and have healthy foliage, trees need only intact bark and a few outer rings of the wood, so a badly decayed tree might not always appear to be a hazard. Therefore, it is important to determine just how much decay is present to determine if the disease has progressed to the point of making the tree hazardous. The presence of decay and a cavity is not necessarily an indication that tree removal is necessary provided that the healthy shell of the trunk surrounding the decayed center is sufficiently thick.

Arborists have tools that can be used to determine what is inside the tree or inside the buttress roots so that a more accurate picture of the tree strength can be obtained. Some of these tools include:

A mallet, used skillfully can help detect a cavity, but it does not tell how much decay is present.

The sound impulse hammer (e.g., Metriguard hammer) or ultrasonic instruments such as the Silvatest and Arborsonic detectors use sound velocity patterns to reveal tree defects.

An increment borer facilitates sampling for study of the annual growth rate of the tree (dendrochronology) and for determining the extent of internal wood decay.

A portable electric drill with a long narrow twist drill bit can be used to determine interior decay and hollow conditions by noting changes in sawdust color, texture, and odor and changes in resistance to penetration at various depths.

A more precise variation of the drill method is provided by the Resistograph F500 decay detection device. A thin, about 1/16 inch diameter probe rotating at high speed is inserted into the tree and penetrates up to a depth of almost 20 inches at constant speed. The changes in power demands on the electric motor resulting from passing through sound wood and decayed wood are printed out on a recording device at the same scale as the distance traversed.

Other detectors employing the concept of wood penetration such as the Densitomat-400, the Decay Detecting Drill (DDD 200), and the Resistograph 1410 operate on the same principle as the Resistograph F500 and also provide a graphic record of the results of drilling.

Electrical resistance measurements inside the tree will show a difference between decayed and healthy wood. The Shigometer is used to detect internal discoloration and decay in the tree and also to provide a relative measure of its vitality.

New non-invasive technology such as thermograpy (measuring a tree's radiant heat), ultrasonic tomography (using sound sensors outside the tree with computer analysis of data), echography (radar), and computed tomography (like the CAT scan used in medicine) are being tried experimentally to detect decay in trees.

As tree decay detection technology advances, it may be possible someday to accurately map out the extent of decay inside the tree. If future technology brings computer-aided 3-dimensional models and species-specific tree strength formulas, it should make hazard tree evaluation even more precise.

Reprinted from "DECAYING TREES CAN BECOME HAZARDS" By John Hartman in the August 6, 2007 edition of the Kentucky Pest News from the Universty of Kentucky, College of Agriculture.

Landscape - Tree Wounds

The following is a good article on dealing with wounds in trees from Kentucky.

Windstorms, heavy thunderstorms, snow loads, and layers of ice are occasional features of Delaware weather that can result in many broken tree limbs and downed trees in the landscape. Much of the fallen wood comes down because the interior of the branch or tree was decayed, but branches with no decay also break and fall. Wood decay in trees almost always begins with an injury to the tree.

Wounds of many types can occur on landscape trees. Weather-related broken branches are significant, but bark injuries, pruning stubs, "too flush" pruning cuts, and cut or damaged roots are also associated with decay problems. One of the most frequent causes of damage to trees in the landscape comes from lawn equipment. Mowers and string trimmers can damage the bark, and if continued, will result in visible wounds at the base of the trunk. Besides restricting the movement of water and nutrients, these wounds become points of entry for insects and wood decay microorganisms.

When an injury or break in the bark exposes the underlying wood, bacteria and fungi in the air, in nearby soil, and on the bark contaminate the wound surface. At the same time, the tree responds to the wound by producing chemical and physical barriers in an attempt to block the invasion of microorganisms and to seal off the damaged area. Organisms which are able to overcome these protective barriers can then colonize and invade the wounded tissues. Among these organisms are the wood decay fungi.

Not all wounds result in extensive decay since trees are frequently able to successfully "compartmentalize" or "wall-off" the decayed area. In many cases, the formation of internal barriers to fungal movement and infection can prevent the decay fungi from spreading. The ability of a tree to internally compartmentalize decay differs from one individual tree to another, although it is also influenced to some extent by tree vigor. Wound-wood provides an external barrier to decay once the wound has completely closed over. The formation of wound-wood may be an indicator of relative tree vigor but it is not necessarily indicative of the tree's resistance to the internal spread of decay. Extensive internal decay may exist behind a well-sealed wound.

The severity of the wound, the tree's vigor and the tree's inherent ability to compartmentalize are important factors in determining the rate the tree is able to seal off the wounded area. Other factors such as time of the year, type of organisms present, and position of the wound also play a role. A healthy tree will normally respond more quickly than one that is stressed. Small wounds may take a growing season to close, while larger wounds may require several growing seasons to close.

The presence of mushrooms at the base of the tree, or conks (bracket or shelf-like fungal structures) on the trunk or branches are the most certain indicators of decay. The absence of these obvious fungal structures (also referred to as "fruiting bodies"), however, does not mean the tree is free of decay; fruiting bodies of some decay organisms do not appear until decay is well advanced while others may go unnoticed because they are small, short-lived, hidden or produced infrequently. Other indicators of decay include old wounds, hollowed out areas, and abnormal swellings or bulges. Decayed wood is usually soft, white, spongy, stringy, and friable; or brown and brittle. Since decay structurally weakens the wood, affected trees become susceptible to wind or other storm damage.

Control. There are no controls or cures once wood decay has begun. Decaying trees should be removed when they become potentially hazardous.

Preventive Measures.

Protect trees and shrubs from injuries due to human activities: Choose a planting site that is away from potential causes of wounds (i.e., away from walkways, driveways, roads). Give the tree plenty of space for growth to maturity. Protect the tree from lawn equipment by controlling the grass and weed growth at the base of the tree. Hand weeding is good, but labor intensive; applying a layer of mulch around, but not against the trunk is most helpful. A plastic tree guard will also protect the trunk, but it should be removed when the trunk diameter approaches that of the tree guard.

Use proper pruning techniques: Prune out injured and diseased branches as soon as they are found. Prune as close as possible to the connecting branch or trunk without cutting into the branch collar. Never leave pruning stubs because these will seldom close over. Do not top trees (refer to the UK publication, ID-55, "WARNING: Topping is Hazardous to Your Tree's Health!").

Practice sanitation: Remove prunings from the tree and do not leave dead wood nearby.

Treat wounds properly and immediately.

Treating recent incidental wounds:

If immediately after the wounding event, the bark and cambium are still moist, carefully press the bark back onto the trunk, making sure the pieces are fitted into their original positions on the tree. If possible, cover the wound with plastic and shade it from the sun to keep it from drying. Secure the bark piece(s) in place using soft cloth strips tied around the tree.

Carefully break away any dry, loose, injured bark. Using a sharp knife, cut back to healthy bark. Make a clean edge between the vigorous bark and exposed wood; even if the wound shape is irregular, avoid cutting into healthy bark.

Treating pruning wounds:

Wound dressings are primarily cosmetic and do not stop decay. A product called Lac Balsam is used by some arborists and may stimulate callus formation. Dressings are needed where spread of oak wilt disease is probable. Otherwise, painting over wounds is generally not recommended.

Treating old wounds:

If callus (wound-wood) has begun to form, carefully remove the old bark until the wound-wood zone is found. Do not cut into the fresh growth or shape the wound.

If wound-wood is absent, treat the wound as if it were a recent injury.

Reprinted from "WOUNDS AND WOOD DECAY OF TREES" By John Hartman in the July 30, 2007 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.