Soil Heat Units Continue to Lag in Western Illinois

Soil heat-unit accumulations from January 1 to June 2, 1997, continue to be very low in many areas of western Illinois, compared with last season. Heat-unit accumulations (base 52 degrees F) at the 4-inch depth are provided for 1996 and 1997 in Figures 2 and 3, respectively. Implications of continued cool soil temperatures include the persistence of wireworm and white grub troubleshooting calls. We anticipate corn rootworm eggs to begin hatching about mid-June and European corn borers to emerge later than "normal." Please refer to this week's article on European corn borers for specifics on expectations for emergence of this insect pest.

Mike Gray, Extension Entomology, (217)333-6652

Figure 2. Actual heat-unit accumulation (4-inch, base 52 degrees F) from January 1 to June 2, 1996.	Figure 3. Actual heat-unit accumulation (4-inch, base 52 degrees F) from January 1 to June 2, 1997.