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Looking Ahead
Volume 54 Number 17 Date 08/21/2009 CORN EARWORM - Significant flights of adults have not materialized at most trap locations, although weather patterns in the last two weeks have been conducive for migration into the state. Reports from the University of Minnesota indicate that source populations in the south-central U.S. are extremely high, with counts exceeding 300 moths per night and larval infestation rates of 100% in field corn. Moderate numbers (44-60 per week) were registered during the August 14-20 monitoring period near Cottage Grove and Sun Prairie in Dane County, possibly signaling the start of the major flight. Trapping network participants are reminded to replace pheromone lures on a weekly basis until the flight has ended. EUROPEAN CORN BORER - Egg deposition is expected to continue in the next 1-2 weeks, depending upon nightly temperatures. According to the European corn borer degree day model, the peak in summer moth activity has occurred in the southern and west-central areas of the state. Corn fields should be inspected closely before 2,100 degree days (base 50°F) are surpassed to determine the need for control of second generation larvae. CORN ROOTWORM - Examination of grain corn in the southern, west-central and east-central districts yielded averages of 0-9 adult rootworms per plant, with economic counts above 0.75 per plant in 20% of surveyed fields. Individual fields with high populations were noted in Buffalo, Calumet, Columbia, Dane, Dodge, Iowa, Grant, Jefferson, Lafayette, Sauk, Sheboygan, St. Croix and Walworth counties from August 4-20, but numbers generally appear to be down from 2008 in most areas. Preliminary results of the annual beetle survey are summarized in the CORN section of this bulletin. SOYBEAN APHID - Final chemical applications, if warranted, should be made in the immediate future. The benefits of treatment diminish beyond the R5 growth stage (beginning seed) and no yield benefit is gained by treating fields at R6 (full seed) or later. Field observations indicate that many acres of soybeans have been sprayed for this pest since the final week of July. WESTERN BEAN CUTWORM - The flight of moths has peaked throughout much the state and is now subsiding. Latest numbers for all 138 Wisconsin pheromone trap locations are provided on the Iowa State WESTERN BEAN CUTWORM MONITORING NETWORK website. Traps distributed in the southern and central counties may be removed at this time. --Krista Hamilton, DATCP Entomologist 
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