Degree days are a useful tool to estimate when common stalk borer larvae begin moving into cornfields. Start scouting corn for larvae when 1,300-1,400 degree days (base 41°F) have accumulated. Temperatures have been variable this spring and degree days have been slowly increasing. Southeastern Iowa reached this important temperature benchmark this week (Fig. 1) and therefore scouting for migrating larvae in corn should begin now to make timely treatment decisions. Consider applications at peak larval movement, or 1,400-1,700 degree days (base 41°F).
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