Western Bean Cutworm Flight Declining– (Christian Krupke and John Obermeyer) -

The western bean cutworm (WBC) trapping season continues, and from the numbers being reported this past week, we are past the peak moth flight. A large percentage of this year’s eggs have been laid and likely hatched, meaning scouting efforts should switch to the small larvae migrating to areas of protection, such as the whorl, before moving to the ear when they get larger. Use this year’s trap catches (see following trap report) and recent history as your guide for prioritizing scouting areas. As you view the “Western Bean Cutworm Adult Pheromone Trap Report”, notice the variability of moth captures, even from traps within close proximity to each other. Although the relationship between trap catches and damage is not particularly strong (i.e., high trap counts do not always mean high damage), traps are a good timing mechanism and presence/absence indicator. When they spike suddenly, it’s time to scout. Fields near largest trap catches should be prioritized for scouting. But that’s about as far as we can take trap counts in assessing damage potential. Areas/fields with damage last year will likely be at most risk this year.

Newly hatched western bean cutworm and whorl leaf damage.

Young western bean cutworm larvae in leaf axil.

Many Bt-traited corn hybrids offer excellent control of WBC and will not require scouting. However, some Bt hybrids do not offer any protection, nor do most varieties of specialty corn, e.g., popcorn, waxy, etc. Scouting is a matter of walking fields and looking for egg masses, generally laid on the top surface of the plant’s uppermost, upright leaves. Concentrate your efforts on pre-tassel/early pollinating corn; this growth stage is preferred by female moths as the young larvae initially feed on pollen. This will be difficult this year because of the field variability due to heavy rains. If more than 5% of plants surveyed have egg masses/live larvae, treatment is advised. If needed, too-early insecticide applications are better than late ones – pyrethroid insecticides will offer enough residual activity in most cases for a few days of killing the tiny hatching larvae as they travel on their way into the plant’s whorl or leaf axils. Happy Scouting!

VIDEO: WBC Scouting Comparison: Spray vs. Non-Spray– (Christian Krupke) -

Western Bean Cutworm Pheromone Trap Report

Precipitation

Temperature

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