Pest News for Week of July 14th

ORNAMENTALS AND TURF

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 (http://msue.anr.msu.edu/news/planting_garden_center_flowers_is_good_for_bees_and_other_beneficial_insect) was published by Dr. Dave Smitley at Michigan State University.

The second, Neonicotinoid Pesticides and Honey Bees (http://cru.cahe.wsu.edu/CEPublications/FS122E/FS122E.pdf) 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 (http://ecoipm.files.wordpress.com/2012/02/franksadof2011reprint.pdf) 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 (https://itunes.apple.com/book/id541182125?mt=11), describes more about management of maple pests and other tree pests. A recent article in Nursery Management (http://ecoipm.files.wordpress.com/2013/03/epson001.pdf) and a fact sheet (http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note25/note25.html) 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.

Maple Mites

Maple Mites
From Dr. Stephen Franks:


Mid-summer damage to maples is often attributed to the twospotted spider mite. However, I visited several nurseries this week and found the culprit was actually the maple mite, Oligonychus aceris. This mite feeds on maples and causes severe damage to maple leaves in midsummer. Leaves are yellow and stippled and mite debris is evident on the underside of leaves. Growers report more damage on “Autumn Blaze” than other maple varieties. However it is common on October Glory and most commonly grown varieties. Management recommendations are the same as for the twospotted spider mite discussed in previous articles in the June 5, 2009 and June 26, 2009 North Carolina Pest News. However, to my knowledge no efficacy tests have been conducted on this particular species. Remember that any damage done to the leaves will remain for the rest of the season and will not be corrected by treatments, nor will the debris wash off from treatments or irrigation. Therefore, be sure to determine if live mites are present before repeating a treatment bases on damage or debris.



For additional information, see Ornamentals and Turf Insect Note No. 25 on twospotted spider mites at Twospotted Spider Mite

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

Pest News

This information comes in weekly from the NCSU Plant Disease and Insect Clinic from mid April until October. The following is an alert from Steve Bambara:

European Red Mites


We haven't seen this mite often in the landscape the last few years, but it has shown up twice in the Plant Disease and Insect Clinic at North Carolina State University over the last two weeks. European red mites usually overwinter in the egg stage. The tiny orange-red colored eggs hatch at about the time when apple trees bloom. The European red mite is an introduced pest that in North Carolina primarily infests apple trees. Although it is reported to infest various shade trees and ornamental plants in the landscape, cherry laurels seem to be the major ornamental plants that European red mites infest. The European red mite causes typical pale stipples on the leaves of their host plants, but this spider mite spins very little webbing. This mite is slightly different from the southern red mite. With your hand lens you should be able to see that the hairs on the back of the mites each arise from a small, white bump whereas the hairs of southern red mites arise from red bumps. I believe any horticultural oil spray should give adequate control. Oils will not significantly harm beneficial predator mite populations are often preferable for this reason. For professionals, most of the favorite miticides will also work.


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

New Mite to Look For

For those of you growing or using Wax Myrtle, be on the lookout for a new mite. This news just in from Dr. Stephen B. Bambara, NCSU- Extension Entomologist

New Mite on Wax Myrtle,
A sample of wax myrtle (Myrica cerifera) arrived in the Plant Disease and Insect Clinic at North Carolina State University this week. Dave Stephan identified an eriophyid mite (Calepitrimerus ceriferaphagus) in the sample that we have not previously seen in North Carolina. It has been reported on wax myrtle in Florida for several years. These microscopic mites cause blistering and puckering of the leaves and an almost mosaic appearance that might be more virus-like. It is presumed that any of the standard miticides would be effective while mites are active.

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