Monday, July 14, 2014

Pest News for Week of July 14th


From: Steve Frank, Extension Entomologist

Bees and Neonicotinoids

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 Mite

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.

Adult maple spider mite. Photo: A. G. Dale.

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 Southeastern US 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.

Maple spider mite egg attached to tree bark. Photo: A. G. Dale.

Maple spider mite damage. Photo: A. G. Dale.

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.