Issue 1, April 24, 2017

Mild Winter & Warm Spring Bugs

The temperatures of the past winter and so far this spring have shown an interesting effect on landscape plants and insects. Although we have had a generally warmer winter and spring than usual, an inordinate amount of the daily high temperatures have been in the 40's degrees F.

Plants tend to develop at temperatures of about 39 degrees F and above, whereas the base temperatures for most insects is about 50 degrees F. As can be seen by the degree-day chart provided by Kelly Estes in this newsletter, we are currently about one week ahead of a normal spring in insect development in northern Illinois. In the southern two-thirds of the state, we are about two weeks ahead of a normal spring for insect development.

However, if one checks cumulative degree-days base 40 degrees F, we are considerably more than two weeks ahead of normal. This has allowed trees, shrubs, and other plants to obtain a head start on insect pests compared to normal years. Emerging spring insects are finding leaves in a later stage of emergence than normal. Previously, this has resulting in considerably less insect feeding damage than in normal years.

When scouting for insects, realize that the same number of insects are likely to produce less damage than usual, so control may not be necessary. Generally, warm springs include "blackberry winters" when we experience a couple of weeks of unseasonably cold temperatures. Highs are typically in the mid 40's to low 50's degrees F during these cold stretches. Although all plant and insect growth is slowed during a "blackberry winter," plants tend to develop faster than insects during these times, serving to increase the disparity between plant and insect development. (Phil Nixon)

Phil Nixon

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