Issue No. 22, Article 9/September 4, 2009
According to the Midwestern Regional Climate Center, precipitation the last two weeks of August averaged nearly 5 inches in the northwest crop reporting district and about 4.5 inches in the northeast district. Growing degree-day (GDD) accumulations from May 20 through September 1 are 275 GDD behind the 11-year average at Freeport and 321 GDD behind at DeKalb. Temperatures have been cooler than normal the past week. There is concern with the later-planted corn about whether it will reach maturity before frost.
White mold in soybeans has become somewhat common throughout the region since August 20. There have been a few reports of fungicide application for white mold control, which will have minimal benefit since infection occurs during flowering. Soybean aphid populations have been steadily increasing the last three weeks, but there have been only a few reports of insecticide spraying. Insecticide treatment for soybean aphids is not recommended past the R5 (beginning seed) soybean growth stage. Soybean sudden death syndrome (SDS) has been observed in some areas of the region.
Jim Morrison, crop systems extension educator, reminds alfalfa growers of the recommended last alfalfa hay harvest dates during the growing season: early September for the northern quarter of Illinois, September 10 for the central half, and September 20 for the southern quarter.
Crop maturation continues to be slowed by cooler-than-normal temperatures. The latest-planted corn is just completing pollination, while the latest-planted soybeans are at R4. The biggest issue currently facing soybean growers is an explosion in soybean aphid numbers. The problem is most serious in the latest-planted soybeans in the northern part of the region; it becomes less of an issue as one goes farther south. Since soybean aphids have seldom been a serious problem this far south, growers have little experience dealing with them.
From a disease standpoint, wet weather and cool temperatures are starting to take their toll on field crops. Soybean fields are seeing a plethora of diseases, including white mold, more downy mildew than usual, and sudden death syndrome. Some areas of the region seem to be impacted more than others. The northeastern part is showing disease in almost every field, with plants dying and yields affected. The central part has scattered fields showing problems, but many look relatively healthy; they just need time to mature before frost.
Soybean aphid populations in the western half of the region are still relatively low. However, populations in the northeastern and southeastern portions have reached threshold levels, and some farmers are spraying. In these areas, higher aphid populations are mostly on earlier-planted beans that are already at R5 and R6, so insecticides are probably not going to be economical.
Diplodia ear rot is starting to show in corn in the southeastern side of the region, where the crop is starting to turn. Corn is generally looking good, but development is generally behind, with crop stages at about 10% to 15% dent and the starch line about halfway down the kernel. The current cool, cloudy weather is not helping corn develop and move toward maturity.
Pastures, however, are growing great with the cool weather, and another cutting is just about baled.