Tracking degree days is a useful tool to estimate when common stalk borer larvae begin moving into cornfields from their overwintering hosts. Foliar insecticide applications, if needed, are only effective when larvae are migrating and exposed. Start scouting corn for larvae when 1,300-1,400 degree days (base 41°F) have accumulated. Counties south of I-80 in Iowa reached this important benchmark this week (Figure 1), and therefore scouting for migrating larvae should begin now to make timely treatment decisions. Stalk borer larvae in northern counties will migrate later in June.
Iowa State University
Hodgson, Erin W., "Stalk Borers Moving in Central and Southern Iowa" (2018). Integrated Crop Management News. 2493.
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