Captures of Black Cutworm Adults: What Type of Trap Do You Have?

April 21, 2000
For the past couple of weeks, we have reported some "intense captures" of black cutworm adults in pheromone traps operated by cooperators around the state. An intense capture is defined as capturing 8 to 9 moths in a 1- to 2-night period. In other words, capturing 10 moths in one night qualifies as an intense capture, as does capturing 6 moths one night and 4 moths the next night. We begin generating projected accumulations of 300 heat units above a base temperature of 50°F after an intense capture to forecast expected dates of cutting by fourth-instar cutworms. These benchmarks of intense captures are essential for generating such forecasts, which alert people to dates when scouting cornfields would be timely.

It is important to understand that intense captures are based on captures in wing traps, which are sticky traps constructed from uniquely shaped cardboard. We have learned recently that some people who ordered black cutworm traps have been provided with bucket traps, which are plastic traps that can be used for capturing a variety of pests. The synthetic sex pheromone used with both types of traps is the same, but the trap design is sufficiently different that trapping efficiency probably is different. In fact, people who have been using the bucket traps have reported much higher captures of black cutworm males, for the most part. For example, one cooperator reported the following captures in a wing trap and bucket trap, respectively, during the three nights of April 15­17: 0 and 16; 0 and 17; and 4 and 4.

Wing trap with pheromone lure for capturing male black cutworms.

Unfortunately, capturing more insects is not necessarily better. A trap that captures more insects is not necessarily a better trap. Trap captures must be based on some research efforts if we want the data to be informative. Consider, if you will, that black-light traps capture lots of insects, but few "thresholds" are based on captures of insects in black-light traps.

When you report numbers of black cutworm adults captured in pheromone traps, please let us know what type of trap you are using. We will generate our cutting-date forecasts based on intense captures in wing traps. However, we are interested in comparing numbers captured in bucket traps with numbers captured in wing traps.

Thanks for all of the information thus far; keep it coming.--Kevin Steffey

Author: Kevin Steffey