Issue 6, May 31, 2011
Intermittent colder weather continues to slow down insect development in Illinois. As stated in an earlier issue of this newsletter, most insects do not develop at temperatures below 50 degrees F with slower development when temperatures are below the low 70's degrees F.
With these extended colder temperatures, be sure to verify insect presence if you are using phenology to time control applications. Plants are continuing to develop and bloom whereas some insects are lagging behind.
This can be used to your advantage. A number of insect pests are staying in stages where they are susceptible to control longer, allowing more time to apply control measures. Another factor is that the cooler temperatures and wetter weather is conducive to fungal diseases of insects providing more control than usual. However, these conditions are also likely to result in an increased effect of other fungi that are diseases of landscape plants. (Phil Nixon)