July 27, 2007    No. 22

Where have all the itch mites gone…

The oak leaf itch mite (Pyemotes herfsi), a species closely related to the straw itch mite and introduced from Europe, appeared in 2004 in numerous communities throughout the Midwest, where it caused itching and painful bites. The mite develops by predating on larvae of gall forming midges. In some areas of the Midwest, populations significantly declined in 2006, with no explanation, except for the appearance of the larvae of a parasitic minute wasp. Whereas populations of midge and mite have declined in recent years, those in Lincoln, Neb., have been maintained in high numbers.

Galls in oak leaves are formed by the midges in early spring (April) when the leaves are ca. one inch long. Female mites with their characteristic distended abdomen appear in the gallsby the end of July. This year we have intensively surveyed oak trees in Manhattan, Kans. and have not found a single gall in any of the numerous oaks inspected. We attribute this disappearance of galls to the very cold snaps that occurred in early spring while midges were swarming and laying eggs on the forming oak leaves. The low temperatures killed the young leaves, thus also eliminating the midge larvae.

Surveys being conducted by entomologists in Lincoln are finding also a drastic reduction in the incidence of galls on oak leaves and so far, just a couple of itch mites (it might be just too early for mites to appear). Most likely, oak leaves in Nebraska were not as affected by the spring weather as those in Kansas. We will continue our interest in learning more about the biology of this itch mite and of its host as most likely they will reappear in high numbers again in years to come. We would also like to hear of any suspected case of these mites in Kansas so we can obtain material for our studies (call or e-mail Dr. Alberto Broce. Ph. 785-532-4745; abroce@ksu.edu ).

Alberto Broce

Soybeans:

Soybean aphids are pictured below from a colony detected in Riley Co. on 18th of July. Dimensions of the colony had not changed on 25th of July. This means the number of aphids per plant and the number of infested plants had not changed. Ants feeding on the honey dew and lady beetles feeding on aphids were observed. Winged aphids were also present which means migration to other parts of the field or different fields is possible and thus monitoring for soybean aphids should be continued.

Corn:

Any one having 6-8 rootworm beetles per plant, please call by phone (785-532-5656) or email (jwhitwor@ksu.edu ) immediately.

Jeff Whitworth and Aqeel Ahmad

Sincerely,

Jeff Whitworth                                                                                        Alberto Broce
Extension Specialist                                                                                Livestock Entomologist
Entomology  (Crops)

Aqeel Ahmad
Research Associate
Entomology