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Issue No. 17/July 15, 2005

Western Bean Cutworm Adults Found in Northwestern Illinois Counties
Since July 1, western bean cutworm moths have been captured in pheromone traps in eight Illinois counties-Adams, Lee, Mercer, Rock Island, Warren, Whiteside, Will, and Winnebago. Cornfields in those counties need to be scouted.

Corn Rootworm Larval Injury Nearing Completion in Urbana
The feeding period for corn rootworm larvae in central Illinois is nearing completion. The recent rains across much of Illinois will very likely increase the number of lodging observations in corn. Typically, yield reductions are most severe when lodging occurs.

Soybean Aphid Densities Are Increasing
Given the current trend of increasing densities and percentages of plants infested with soybean aphids, it is quite possible that soybean fields in northern Illinois will benefit from insecticide applications within the next week or two. Be very careful with any application to avoid killing honey bees.

Preliminary Results from a Spider Mite Control Experiment
The recent, long-hoped-for rains may reduce the impact that twospotted spider mites could have on soybean yields in some areas. But continue scouting for the pest in soybeans. A return to hotter, drier conditions will enable the existing population to increase in size again unless a fungal organism establishes itself in the population and begins an epizootic.

Crop Recovery After Rain
While rain in the middle of the growing season will probably improve crop ratings somewhat, can we expect water now to undo the damage already done to the corn crop? Most previous research doesn't provide good answers. With regard to soybeans, the rain (where it has fallen) has arrived in time to restore crop prospects to near-normal levels. But there will need to be continued water supply to ensure that more flowers will produce pods, that pods will stay on the plant, and that seeds will fill.

Regional Reports
Reports are provided this issue for east-central, northern, southern, and west-central Illinois.