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Friday, September 11, 2009

Caterpillars in blueberries (and other woody perenials)

Redhumped caterpilars (Schizura concinna), Lacy L. Hyche, Auburn University, Bugwood.

As weather really starts feeling like fall, caterpillars are showing up in NC blueberries. Most common and noticeable are redhumped caterpillars and yellownecked caterpillars.

Yellownecked caterpillars (Datana spp.), from Debbie Roos, Growing Small Farms:

I had a phone conversation about these insects with Bill Cline, blueberry and muscadine pathologist, immediately preceeded by an email from Benny Bloodworth, his technician. Both had the same question: what are these caterpillars and what should growers do about them?

Both species of caterpillars can aggregate when feeding and large populations can result in defoliation of the plants they are feeding on. The real question about what to do depends on the grower. Most large, commerical blueberry growers apply fall treatments for sharpnosed leafhoppers at the end of September or the beginning of October. Some pesticides used for leafhoppers will also effect caterpillars. If a large caterpillar infestation is present this time of year, one of these materials should be selected as the leafhopper treatment of choice. See the NC Ag Chem Manual for more information.  A note on pesticide recommendations.

Organic management is more challenging. There are effective organic controls for caterpillars (a lot of them), but there are little to no materials for leafhoppers. As I mentioned when talking to Bill today, organic blueberry growers are going to have to think differently about their production system than conventional growers. It will not be possible to just take a "spray schedule" and translate it into organic pesticides. These growers will need to maximize cultural management (in this case removing infested plants immediately upon noticing infection) and monitor carefully for pests because organic pesticides behave differently than conventional ones and must be carefully timed to be effective. Of course, conventional growers should be monitoring pests and minimizing pressure via cultural control, too! My IPM mantra is minimize, monitor, and manage, which I'll address in more detail in a post over the weekend.

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