The long anticipated, eagerly awaited, bollworm flight appears to be here. Who would be excited about getting damaging levels of worms in our crops, you ask? That’s a really good question. In fact, some folks couldn’t wait. They went ahead and threw a pyrethroid in with that fungicide application. I saw in the last few weeks where some folks just sprayed because they wanted to “clean up” some “loopers, bean leaf beetles and stink bugs” and other assorted non-damaging levels of low population/non-existent pests.
To this point, the level of insect activity is the lowest I’ve seen in a long time, which brings me to the value of making predictions about insect activity—a very mild winter, early spring, and higher than normal temperatures all sound like the setting-up for a really bad insect year—at least that’s what I was quoted saying in every possible news media available. It seemed inevitable that insects would be bad. Nobody likes to admit to being wrong and sounding a little foolish, but when the shoe fits, you have to wear it I guess. I take comfort only in the fact that I wasn’t the only one, and in a few cases, some insect pests have been bad—blister beetles and grasshoppers are the only two that come to mind.
Anyway, back to the worm flight. Our moth trap numbers jumped big last week; late in the week our weekly moth trap count tripled from the previous week. We run the traps twice a week on Mondays and Thursdays. After the moth traps were dumped on Thursday, we drove by a few of the traps on Friday and there were well over 100 moths per trap on a one night catch. That’s a lot of moths for one night obviously, and this tells me the July flight we get every year is here. Several folks indicated to me last week that they have started kicking up a lot of moths which we also observed in our sweep net sampling in soybeans late in the week. In south Arkansas, we are seeing eggs and small larvae already showing up in cotton as well as soybeans. I suspect a lot of fields will be treated for bollworm in the coming 2 weeks as this flight moves across the state.
We’ve got really good beneficial insect numbers, and they may actually provide protection on some fields and prevent an application in many cases where pest populations are marginal. Remember, we don’t treat small worms in soybeans as we do in cotton. Small larvae don’t cause very much damage in soybeans and by waiting, we get full use of the predators and parasites giving them the opportunity to get the larval population under control. Larval pests are much easier to control in soybeans than cotton because they are much more exposed to insecticide applications. They don’t have anywhere to hide like they do in cotton (inside a square, bloom, boll, or under a stuck dried bloom).
I’m sticking with my recommendation to use insecticides that won’t disrupt the beneficial insect population in soybeans. Products like Belt, Steward, Tracer, etc. will effectively control these worms and leave our beneficials intact, and most importantly, are much more effective for control of caterpillar pests than pyrethroids. Our threshold is 9 bollworms per 25 sweeps.
Finally, back to predictions. I think caterpillar pests like loopers, armyworms and bollworms will continue to be a problem the rest of the season. Dry weather and high temperatures favor this prediction too. At least we have an early crop and will escape these populations on a large part of our acreage.
I guess I’ll never learn about making predictions. The late Dr. Caviness once stated on a soybean tour I attended that only two kinds of people make predictions on soybean yields (and I figure insect problems fall along the same line), fools and newcomers—I’m no newcomer. Anyway, scout soybeans closely right now, particularly late planted beans that are blooming and not lapping. Don’t let the pests sneak up on you now.