Scouting and Thresholds

Scouting should begin when moths are first noticed in the pheromone traps. In corn, check 20 consecutive plants at five locations. The University of Nebraska recommends that if 8 percent of the plants have an egg mass or young larvae are found in the tassel, consider applying an insecticide. Timing of the application is critical. If the tassel has not emerged when the eggs hatch, they will move into the whorl and feed on the developing pollen grains in the tassel. As the tassel emerges, the larvae will move down the plant to the green silks and then into the silk channel to feed on the developing ear.

If an insecticide is needed, apply it when 90 to 95 percent of the tassels have emerged. If the tassels have already emerged, the application should be timed for when 70-90 percent of the eggs have hatched. Once the larvae reach the ear tip, control is nearly impossible. If an insecticide application is needed, cornfields should be checked for the presence of spider mite colonies. If mites are found, select a product that does not stimulate mite flare ups (increased population growth).

Determining Peak Flight

Monitoring should continue until the peak flight has occurred. To determine if a peak flight has occurred, look at the daily trap catches in your area. If you see a marked increase followed by decrease (1-3 days of declining numbers) in the moths captured this may indicate a peak flight. If you see the decrease, consider other factors that may have caused this decrease, (e.g. rainfall, high winds, and cold temperatures). These environmental factors may decrease the number of moths in flight and thus you would not be seeing a true peak flight. If you are not sure if you have a peak flight, continue monitoring for at least 7 days to see if you see a rebound in the numbers. There are sometimes secondary peak flights.

Once we have passed peak flight, egg laying will decrease with the decrease in moth numbers. Scouting should continue for 7-10 days after the peak flight.

Because we are gathering data on this new pest, we want to track the entire moth flight. Please continue monitoring the trap until August 15.

(Note: This information is based on our current understanding of this new pest. Research is being conducted to improve the scouting and management guidelines.)