Plant and Insect Diagnostic Clinic Update - July 30, 2008


  • The Japanese beetle remains the "hot" pest of the week. Four new counties (Bremer, Buchanan, Greene, Pottawatamie) were added to the known distribution of Japanese beetle in the state. The peak of JB emergence is rapidly passing, but beetles will remain until almost the middle of August. Control is still possible, though spraying severely defoliated plants like the tree below is a revenge treatment of little benefit.

Japanese Beetle Defoliation.  Photo by Jeff WendelJapanese Beetle Defoliation. Photo by Jeff Wendel

  • Bagworms are still a common topic of calls and messages. We are rapidly approaching the point when caterpillars will tie the bags to twigs and seal them shut for the miracle of metamorphosis to take place. Spraying after the caterpillars stop feeding (when the bags are tied to twigs) is a waste of time and resources, and probably does more harm than good! See the Horticulture and Home Pest News from June 20, 2007.

  • The cicada killer wasps are still creating quite a buzz. For more details about the life cycle see our Iowa Insect Information Notes. It is logical to be concerned about large wasps, but the cicada killer, like other solitary wasps, won't sting unless handled or threatened. A nest in an out of the way location can be left alone. Wasps nesting in high traffic areas can be controlled by placing an insecticide dust (e.g., Sevin or permethrin) in and around the nest entrance during the night.

Cicada Killer Wasp and Cicada.  Photo by MJ Hatfield.Cicada Killer Wasp and Cicada. Photo by MJ Hatfield.


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