It has been unusually quiet so far this year for insect reports. Late last week, I received a report of spider mite activity in soybean in south-central Illinois near Macedonia. Most of the state received a healthy (or even unhealthy) dose of rain at least once or twice in the last week – that will do more to eliminate spider mites as a threat than even the best miticides available. Cooler temperatures will also help. If you are in an area that remains hot and dry and have spider mites, evaluate the potential for continued growth in the population based on the weather forecast and the extent of current injury to make a control decision.

I’ve also received a report that grape colaspis are active again in at least a limited area near Mt. Auburn where they have been a problem in the past. Affected plants will exhibit nutrient deficiency symptoms, especially purpling of the lower leaves and often concentrated on higher/better drained portions of the fields. Digging up the plants will reveal the larvae, which resemble tiny white grubs. By this point, affected plants will be noticeably stunted relative to surrounding, healthy plants, and the larvae may be close to finishing their development and emerging as adults. There is no effective rescue treatment for this pest in corn.

We will again be distributing yellow sticky traps to anyone who wishes to participate in our regional corn rootworm monitoring network. If that applies to you, send me an email (nseiter@illinois.edu) with “rootworm monitoring” in the subject heading.