Plant and Insect Diagnostic Clinic Update - August 26, 2009

The following are highlights and updates about samples and questions received in the Clinic during the past two weeks:


Yellowjacket wasps continue to swarm from holes in the ground or house foundation.  They will freeze to death soon, but if they are in a high traffic area, now is the time to treat the colony with insecticide dust to reduce the threat of being stung.  See the Yellowjacket Wasp Insect Note for more details.

We have also received about a half-dozen samples of strawberry root weevils.  This is normally an accidental invader in mid-summer, but seems to be putting in a late appearance this year.  The small brownish-black, light bulb shaped beetles are harmless indoors and can be swept back outside.  Please see the strawberry root weevil insect note for more information.

Fruit flies are certainly a problem in my kitchen with the abundance of fruit and vegetable I did not eat quickly enough.  Larvae can develop in rotting fruit, but are also commonly found anywhere with wet decaying organic matter - including floor drains.  Please see our Fruit Fly insect note for tips on how to locate the larval feeding area and eliminate the fly problem.

Fruit fly.

Fruit fly.


Now is the time of the year that people see the large and impressive imperial moth caterpillar. See the photo below. The imperial moth is moderately common but very sporadic in Iowa (more specimens some years than others). The caterpillars feed on the foliage of many different trees (basswood, birch, cedar, elm, hickory, honeylocust, maple, oak, pine) but the numbers are usually too few to make a difference and they are not considered to be a pest of Iowa's trees. The caterpillars are highly variable in color. Control is usually not required, especially when the caterpillar is already fully grown and the damage is already done. The moth stage will not appear until next spring and will be a large yellow moth marked with purplish-brown spots. Click here for more information about the Imperial moth.




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