Description: Western Bean Cutworms lay eggs mid July. These eggs are in clusters ranging from 5 to 200 on the top surface of the leaf in the top ⅓ of the corn plant.  Eggs will take 5-7 days to develop and in that time they will change from tan to purple.  

group of mostly purple small eggs

Scouting: Look for egg clusters in the upper 3-4 leaves of the corn plant and even tassels. Check 20 plants in multiple areas within the field to get an idea of what the population of the eggs are. Young larvae are approximately 0.25 inches in length, they are tan with a faint diamond shaped pattern on their backs. When maturing they become pinkish tan, pale brown and can get as big as 1.5 inches long. As they emerge from their eggs, they will move down the plant and start feeding on silks and the developing ear. 


Management: If 4% of the plants have larvae or egg clusters consider an insecticide treatment. If an insecticide is needed, wait till 90-95% of the tassels have emerged. If tassels have emerged then the application should be timed when 70-90% of the eggs have hatched for best control. Any larvae that are in the ear feeding are nearly impossible to control. Also consider planting a hybrid with Bt traits such as Smartstaxs.