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Corn
Volume 58 Number 2 Date 05/09/2013 BLACK CUTWORM - A spring migration that began four weeks ago has to date yielded 184 moths in 30 traps. The moths originated in the south-central U.S. and were carried into the state on storm fronts beginning April 15. Early-season migrations such as this one can be precursors to damaging cutworm populations in May and June when corn planting and weed control are delayed. Based on the low number of moths arriving in past weeks, the risk of cutworm damage to emerging corn appears low for now. This forecast could change with an influx of moths this month. The map below summarizes cumulative moth counts from April 15-May 8. EUROPEAN CORN BORER - Larval counts last September were historically low, averaging only 0.03 per plant statewide. In 10 previous years, the state average count was 0.17 borer per plant compared to an economic threshold of 1.0 per plant. Significant for 2013 is the fact that the record low population of overwintered larvae should produce an extremely small flight of spring moths in June, and a relatively low population of first generation borers. The 2012 state average corn borer count was the lowest documented since annual surveys began in 1942. SEEDCORN MAGGOT - Emergence of adult flies from the soil began by April 27 in advanced southern areas of the state, following the accumulation of 200 degree days (base 39°F). As stated last week, outbreaks of this pest are sporadic but usually occur in years when seed germination is delayed by cold, wet soils, which could be the case in the central and northern areas of the state this spring. TRUE ARMYWORM - The first indication of armyworm arrival was on April 29 near Janesville in Rock County. Trap counts since then have been low, although it is likely that more were blown into the state with black cutworm moths, leafhoppers and other migratory insects. -- Krista Hamilton, DATCP Entomologist 
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