Monday, April 15, 2013

Pest Alert for Week of April 14


From: Steve Frank, Extension Entomologist

Ambrosia Beetles

Ambrosia beetle activity has been sporadic this year. Remember those two 70-degree days in January? I had reports of ambrosia beetle attacks on those two days. Since then I have had a few other reports of beetles in traps or occasional attacks. At our research nursery, Raleigh, however, we hadn’t captured any until this week. Then Tuesday the traps filled up and two trees were hit. It seems ambrosia beetles are finally out in Raleigh and we had similar reports from the mountains and foothills. 

Ambrosia beetle management starts with reducing plant stress. In particular we have found that trees with too much water are preferentially attacked. It is easy to overwater this time of year when transpiration and evaporation are low. The next step is preventive applications of permethrin. Apply permethrin to tree trunks and try to avoid spraying the canopy. Our research shows that spraying tree canopies results in spider mite outbreaks later in the year (see the paper here: 

Cankerworms Hatching

Cankerworms were very abundant last spring and we predict the same this year. Cankerworms eggs were laid over the winter and just started hatching in Raleigh last week. You can see the tiny caterpillars if you shake branches or just watch for them dangling below trees. They feed on many hardwood tree species but willow oaks seem to be damaged most heavily. We have written a lot on the biology and management of these critters. See a recent article in American Nurseryman ( You can find information and links to other articles on our dedicated Cankerworm Project webpage ( The important thing to remember is that they only feed for 4 to 6 weeks and only have one generation per year. By the time they get big and start defoliating trees they are about to quit and pupate in the soil until fall. The best management tactic is tree banding in the fall when adults are active. This time of year there is not much to do especially for large trees.

Eastern Tent Caterpillars

Eastern tent caterpillars hatched in the past couple weeks and have already established big nests. The easiest way to deal with tent caterpillars is to prune out the nests. Eastern tent caterpillars make nests in the crotch of trees. (Fall webworms make nests at the end of branches.) So it you can’t remove the nest you can poke it with a pole pruner. This destroys the nest so many caterpillars fall to the ground and others get eaten by birds. Opening the nest also lets parasitoids in to kill the caterpillars. For severe infestations there are some insecticide options. Products containing Bacillus thuringiensis (Bt) are effective against caterpillars. Other active ingredients labeled for caterpillar control include spinosad, Beauveria bassiana, acetamiprid, acephate, azadirachtin, and bifenthrin. Keep in mind that these caterpillars spend most of their time in a water-proof nest so contacting them is difficult. This limits the efficacy of many insecticide applications.

Extension Resources Online

We have many extension resources such as factsheets, articles, pest news, and presentations consolidated as links on my website ( In addition, you can visit the site to read my blog or twitter feeds. You can also sign up to follow my pest alert Twitter feed @OrnaPests and my general ecology and IPM twitter feed @ecoIPM via Twitter or by clicking the ‘Follow’ buttons on my website. @Ornapests provides short timely alerts when new pests become active in the field accompanied by pictures and links to management information. I recently posted “pdf” files of about a dozen articles I have written for industry magazines and a new free book on the management of tree pests in nurseries and landscapes (

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