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Corn
Volume 63 Number 3 Date 05/17/2018 BLACK CUTWORM - Larvae resulting from the spring migration are expected to reach the destructive corn-cutting stages by May 23 across much of southern Wisconsin. Based on accumulated degree days since the first significant moth captures on April 30, by next week, some larval offspring will have developed to the fourth instar, the stage at which the ½-inch caterpillars begin cutting plant stems. Signs of cutworm activity, including small, irregular holes in the leaves and cut plants, could be encountered in emerging corn. Fields with preexisting winter annual weed infestations and those affected by spring flooding should be closely monitored. Summarized in the map below are cumulative black cutworm counts for the period of May 10-16. The spring trapping survey has so far captured 1,162 moths in 47 traps, with a high individual count of 92 moths near Platteville in Grant County. Approximately 1,730 moths in 45 traps had been collected by this time last year. EUROPEAN CORN BORER - A few early spring adults could emerge next week in locations such as Beloit, La Crosse and Spring Green where the 374 degree days (modified base 50°F) required for corn borer flight to begin are likely to be surpassed. Black light trappers are advised to carefully examine trap contents during the next two weeks for the first ECB moths. -- Krista Hamilton, DATCP Entomologist 
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