Issue 2, April 30, 2012
Weather & Insect Emergence
Cooler weather over the last two weeks has helped bring the insect activity pattern closer to normal. Based on growing degree days with a base temperature of 50 degrees F, southern Illinois is slightly over two weeks ahead of last year, central Illinois is three weeks early, and northern Illinois is slightly over four weeks early. Two weeks ago, growing degree days in southern Illinois were almost four weeks ahead of 2011, central Illinois four weeks early, and northern Illinois over five weeks early. The spring of 2011 was relatively normal into May.
Phenologically, northern Illinois insect emergence should be similar to that of full bloom of bridal wreath spirea, Spiraea X vanhouttei. Central Illinois insect emergence should be similar to that of the end of bridal wreath spirea bloom. Southern Illinois insect emergence should be similar to that of full bloom of mock orange, Philadelphus. Although these plants have already bloomed this year and some of the insects associated with that blooming period may have already emerged, the cool weather of the last few weeks should have kept the insects from developing beyond their susceptible control windows. (Phil Nixon)