Scientific American is reporting from Reuters that Home Depot, BJ’s Wholesale, and other smaller retailers will soon require vendors to label plants that have been treated with neonicotinoid insecticides. Neonicotinoids are among the most commonly used insecticides on ornamental crops and all crops. This class of chemicals includes imidacloprid, dinotefuran, thiamethoxam, acetamiprid, clothianidin, and others. Controversy around neonics revolves around their potential to harm bees and other pollinators. Like most insecticides, neonics are acutely toxic to bees on contact. Since neonicotinoids move systemically within plant tissue they can also contaminate flower pollen and nectar that bees consume. Though this can negatively affect individual bees the effects on bee populations is not yet known (and very hard to measure). Information about this was recently reviewed in two extension publications and a scientific paper. Of course there is no news that these outlets will stop selling neonicotinoids to consumers. Nursery and greenhouse growers who produce crops for retail outlets should start figuring out alternative insecticides as this trend is likely to spread.
This time of year the results of potato leafhopper feeding show up particularly in nurseries.Potato leafhoppers are a native insect but mimic retired folks because they spend winters in Florida and the Gulf coast. From there adult potato leafhoppers, Empoasca fabae, migrate between late April and early June. Female potato leafhoppers oviposit along leaf veins and clustered at the base of leaves near the petiole. There are five to six overlapping generations per year.
Injury is caused by salivary phytotoxins injected into the plant phloem during feeding. Damaged leaves can have necrotic margins and severe cupping or stunting referred to as ‘hopperburn’. Leafhopper feeding on buds and meristems causes loss of apical dominance and a witch’s ’broom’ can develop in which many stems grow from the apical tip of nursery trees and may require extra pruning to improve aesthetics and train a central leader.
Host plant resistance can play an important role in managing potato leafhopper damage. In general, red maple cultivars that break bud earliest in spring sustain the least feeding injury by the conclusion of the growing season. Higher levels of foliar nutrient content, particularly nitrogen, will also predispose maples to injury due to increased oviposition, nymphal survival, and development rate so don’t go crazy with early fertilization. Mites, aphids, and other pests also appreciate high nitrogen provided by fertilizer.
Potato leafhopper arrival can be monitored in spring using yellow sticky cards deployed above the canopy of young maple crop or in close proximity to outer canopy foliage. Arrival of migratory potato leafhopper adults usually corresponds to around 600 degree-days. Pyrethroids can be applied bi-weekly starting at peak trap catch. However, many applications of pyrethroids may be needed to reduce leafhopper populations and damage. Pyrethroids can also cause outbreaks of other pests like mites by killing predators in the canopy. Alternatively, recent research indicates that systemic neonicotinoid insecticides applied as a drench can provide effective leafhopper control for two years. Systemic insecticide drenches need to be applied before leafhopper arrival and can help protect natural enemies within the nursery. Even though neonics can in some cases induce mite outbreaks I think it is still a less intensive approach in terms of both labor, active ingredient, and effects on non-target organisms. More information about maple pest management can be found in a recent Journal of IPM paper and free iBook IPM for Common Deciduous Trees in Southeaster US Nursery Production.
Japanese maple scale, Lopholeucaspis japonica , is active now and much of the summer. It is a small, oystershell-shaped, armored scale introduced to the U.S. from Asia. Japanese maple scale is found in several eastern U.S. states, including CT, DE, GA, KY, MD, NC, NJ, PA, RI, TN and VA, as well as Washington D.C.. Japanese maple scale has a wide host range that in addition to maples (e.g., Japanese maples, Red maples, Paperbark maples, and sugar maples), includes Amelanchier, Camellia, Carpinus, Cercis, Cladrastis, Cornus, Cotoneaster, Euonymus, Fraxinus, Gledistia, Ilex, Itea, Ligustrum, Magnolia, Malus, Prunus, Pyracantha, Pyrus, Salix, Stewartia, Styrax, Syringa, Tilia, Ulmus, Zelkova, and others.
Although the lifecycle of this pest has not been fully examined, two generations a year are expected in the mid-southern U.S. First generation crawlers emerge in mid-May, and the second generation in early August but there may be more. Management efforts are complicated by the extended crawler emergence that results in first and second generational overlap. Thus, the most recent sample we received had every stage – egg to adult- present at the same time.
Adult scales and crawlers are very small and most readily observed on bark of dormant deciduous host plants, but can also be found on foliage. The waxy coating on the body of male Japanese maple scales is white and females, eggs, and crawlers are lavender. The most work on this scale has been done by Paula Shrewsbury and Stanton Gill at the University of Maryland. There is also information on JMS and other maple pests in our new book here: http://ecoipm.com/extension/extension-resources/
A link to the UMD fact sheet is here: http://ipmnet.umd.edu/nursery/docs/JapaneseMapleScale-UMD2011.pdf
Two recent publications will help growers, landscapers, retail outlets, and the public understand the risks and benefits of neonicotinoid insecticides without the hype. These extension publications provide a balanced account of the current research and restrictions. Planting garden center flowers is good for bees and other beneficial insects was published by Dr. Dave Smitley at Michigan State University.
The second Neonicotinoid Pesticides and Honey Bees by Timothy Lawrence and Walter Sheppard at Washington State University provides an accessible literature review of research related to honey bee exposure to neonicotinoids.
Maple spider mites (Oligonychus aceris) are common and damaging pests of maple trees throughout the Eastern United States. These spider mites overwinter on the trunk and
branches of maple trees and migrate to the underside of leaves in the spring. Once there, they use their mouthparts to pierce leaf cells and feed on cell sap. This causes fine flecking called stippling and eventually leaves turn gray or brown after heavy feeding. Maple spider mites have multiple generations per year which enables them to become quite abundant during a single season. These pests are a more serious problem in nurseries due to the close proximity of potted trees and applications of broad spectrum insecticides like permethrin. For example, our research has shown that applications of permethrin targeting ambrosia beetles can wipe out natural enemies and result in secondary maple spider mite outbreaks. Maple spider mites can also be abundant on landscape trees. Trees in parking lots and along roads are most likely to be infested.
A hand lens or stereo microscope is necessary for correct identification of these mites but damage is a good indicator of infestation. They are dark brown or red with hairs along their backs and have eight legs while some immature forms exhibit green coloration and have six legs. Red eggs of these mites can be found on tree limbs and yellow or clear eggs can be found on leaf surfaces. Treatment for these pests includes foliar applications of acaricides. Maple cultivars differ in susceptibility to maple spider mites and other maple pests like leafhoppers. A chapter in a recent free ibook IPM for Select Deciduous Trees in Southern Nursery Production describes more
about management of maple pests and other tree pests. A recent article in Nursery Management and a fact sheet describes mite biology and management. This time of year trees may not be sold until fall so the condition of leaves is not as much of an issue. On landscape trees mite damage reduces fall color and summer color because leaves are gray, yellow, or brown instead of green.
Guest blog by April Hamblin an MS student in our lab who is often sweating in the urban heat as she conducts research to determine how urbanization affects native bee communities. She writes periodic posts here and on yourwildlife.com about her research and bee natural history.
Do you sweat in this North Carolina heat and humidity? If you sweat enough, beautiful bees may come by and give you a light kiss. These bees in the family Halictidae are known as sweat bees because they drink the salts from your sweat. They are very small and often mistaken as flies. If swatted at, many have stingers so small that they cannot penetrate our skin, but if they do, you may feel a tiny twinge of pain that soon leaves as fast as the bees fly away. So when you’re outside this summer sweating up a storm, watch for your friend and important pollinator, the sweat bee.
While many sweat bees are dark black and blue, some are even green! This common species, Augochlora pura, is found in North Carolina along with over 500 species of native bees! In this photograph, this sweat bee is extending her tongue to the left, which is how she would suck the salts from your sweat. Photographed by Sam Droege, USGA. For more beautiful photographs of native bees, please visit: https://www.flickr.com/photos/usgsbiml/
This time of year arborvitae plants may get a little shabby. Many branches get short brown
tips. Other branches may turn brown and just hang on the plant. Arborvitae leaf miners, Argyresthia spp., are tiny moths responsible for brown tips. Moths lay eggs on new growth which is why the tips of plants are damaged. Larvae burrow into leaf scales and mine foliage as they feed and develop.
Larvae overwinter in the mines and resume feeding in spring. Damage is most evident in winter and early spring so the damage you see now is likely from mines initiated last year. Mines can be differentiated from other damage by looking for exit holes and by opening damaged tips to look for larvae.
If you have larger brown branches that are hanging, barely attached to the tree, you
probably have damage from Phloeosinus spp. bark beetles. Commonly called cypress bark beetles, eastern species attack arborvitae. These beetles chew branches 15-30 cm from the tip making a groove or short tunnel that weakens the branch. The branch then breaks easily in the wind and turns brown, a condition called flagging. You can look for the hollowed end of branches you suspect were damaged by these beetles.