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Looking Ahead
Volume 54 Number 18 Date 08/28/2009 EUROPEAN CORN BORER - The treatment period for second generation corn borers remains open for another 1-2 weeks in the southern and central counties. Final inspections should be performed at this time, before 2,100 degree days (base 50°F) are surpassed. Due to the variation in development in different areas of the state, sweet corn growers are advised to examine their fields carefully and base control decisions on the specific conditions observed. Treatment of late-planted processing sweet corn is justifiable when 4-5% of plants show egg masses or small larvae. WESTERN BEAN CUTWORM - Larvae are still active in Wisconsin corn fields. Most are in the late instars and should complete development by early September. Economic populations were detected this week in Adams, Green Lake, Marquette, Monroe, Rock and Waushara counties, where 5-45% of ear tips were infested. Several of the surveyed fields would have benefitted from treatment at tassel emergence, but corn is well beyond this period now and chemical control is no longer of value. SOYBEAN APHID - Surveys of soybeans in the southern and central counties, as well as reports from County Extension personnel and consultants, indicate that populations have surged above treatment thresholds in the last 2-3 weeks. Some late-planted soybeans may still qualify for treatment, but these must be evaluated in the immediate future. The benefits of treatment diminish beyond the R5 growth stage (beginning seed) and no yield advantage is gained by spraying fields at R6 (full seed) or later. CORN ROOTWORM - The annual beetle survey is nearly complete, except for the northwest, north-central and northeast agricultural districts. Reports from the southeast, southwest and east-central areas show a substantial reduction in numbers as compared to 2008. Preliminary results of the survey are summarized in the CORN section of this bulletin. --Krista Hamilton, DATCP Entomologist 
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