No. 17/July 17, 2003|
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|IN THIS ISSUE:|
|Questions About Japanese Beetles Abound|
The unknowns about Japanese beetles and their potential effect on corn yields outweighed the knowns this week. If a field has adequate moisture and silk extension is not impeded, silks that are 1/2 inch or longer can still intercept pollen. For soybeans, it's important to scout flowering fields to determine the presence of Japanese beetles and percentage of defoliation to decide whether control is justified. Suggested insecticides for control of Japanese beetles in soybeans are listed.
|Western Corn Rootworm Emergence Delayed|
Though emergence of adult western corn rootworms is well under way, it is delayed compared with recent years. Added pressure is placed on soil insecticides when planting occurs in early April and the larval feeding period is extended through mid- to late July, which is the scenario in much of central Illinois. Please tell us of any confirmed cases of larval injury in first-year cornfields, especially in western and northwestern counties.
|The Moths of Summer Are Back|
As we near the end of July, moth flights will be increasing throughout the state. Details of corn earworm, southwestern corn borer, fall armyworm, and second-generation European corn borer--four of the prominent moth pests of corn--are described here.
|Notes on Other Insects|
Comments are provided for bean leaf beetle, soybean aphid, and twospotted spider mite. Continuing reports from the field are valuable and appreciated.
|Phytophthora sojae Sensitivity to Metalaxyl and Mefenoxam|
Preliminary results of studies in Illinois, Ohio, and Ontario suggest that metalaxyl and mefenoxam continue to be effective compounds for control of early-season infection of soybean seed and seedlings by P. sojae.
|Root Rot in Soybeans|
Phytophthora sojae (newly classified as a "fungus-like organism") has appeared in soybeans, especially across the central part of Illinois. P. sojae is a tricky disease and can attack and kill soybeans throughout the season. The primary method of management is the use of resistant varieties.
|A Good Day in the Field|
What makes a "good day" for corn and soybean crops? The influences of temperature, sunlight, and water on crop development and subsequent yields are detailed.
Regional reports are provided this issue for northern and west-central Illinois.
|Soybean Aphid Update|
Reports of dramatic densities of soybean aphids in northern Illinois have been validated by sampling of 14 fields in Kendall County that have been studied since 2001. Whether to use an insecticide application remains a tricky decision; pod set is the critical stage to be protected. Sampling twice over four to five days is recommended before choosing to spray; additional guidelines are provided here.