Insects in Trees

Home Grown  by Keith Reed
The Payne County Extension office has been overwhelmed the last few days with all kinds of tree and shrub issues. We’ve already touched on the premature leaf drop so this week we will focus on the other major concern right now, leaf eating insects in a variety of tree and shrub species.

About this time of year, we often see a webworm outbreak. If you’ve seen that, you know that while it look unpleasant, webworms don’t cause any long term damage to the trees. Redbud leaf-rollers are another example that has produced hundreds of inquiries to our office over the last few years. It looks like a big problem at the time, but the trees recover just fine the next season.

Right now, the two pests mentioned above aren’t much of a problem, but other leaf-eating caterpillars are showing up in high numbers on a variety of plants. This can be shocking due to the noticeable damage over a short period of time. Except in very rare circumstances, there is no need to treat for these pests.

There is another pest causing a different set of problems right now. Aphids, tiny insects that live primarily on the bottom side of leaves, are at population levels not seen in several years. These insects pierce the leaf of the plant and feed on the plants by sucking the plant sugars out.

Most people never see the aphids, but they see evidence of them; a sticky substance all over everything in an area. This is honeydew (aphid poop) and while it is not harmful, it can be quite a nuisance. This is especially true around patios and other outdoor entertainment areas.

Just like with the caterpillars, aphids are going to cause any long-term damage to plants. Typically, beneficial insects will move in and begin feeding on heavy populations, reducing their numbers. Combine this with a significant cold front and the problem goes away as quickly as it began.

If you have a situation where the honeydew becomes unmanageable, aphids can be killed with a number of all-purpose insecticides. If you do treat, understand that in addition to killing the aphids, you will also kill the beneficial insects already working to control them. Expect the aphid numbers to then rebound much quicker than the beneficial insects, potentially causing higher numbers of pests than were present before treatment.

Pesticides are a valuable tool when used appropriately and applied correctly. However, they should only be used when necessary if we have expectations of seeing them remain available and valuable for our use.

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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