The cotton insect situation has changed a lot in the last couple of weeks, and has reached something of a turning point, says Angus Catchot, associate Extension professor of entomology and plant pathology at Mississippi State University.
“Plant bugs have always been our No. 1 priority,” he said at the annual joint meeting of the Mississippi Boll Weevil Management Corporation and the Mississippi Farm Bureau Federation’s Cotton Policy Committee. “This year, we started off with a bit lighter than normal pressure, though we still had quite a few farmers spraying prior to bloom.
“We still have some areas of the Delta where pressure is moderate, and others where they’ve been extra tough.
We’ve made a real effort the last two years to provide producers the most up-to-date information on plant bugs.
“One of the things we’ve preached hard is that once we get into bloom and when you’ve got nymphs embedded in the crop, to use mixtures — add a pyrethroid to your OPs. Time after time, we’re seeing better results with a mix than using an OP alone.”
While Diamond IGR is an expensive material at $1 per ounce, Catchot says, “We’ve had very good results with it and it has a good residual. I’m not saying use it every time you spray, but maybe every other time.”
Because growers have been doing a good job with tank mixes, plant bug control has been much better, he notes. “But if you’ve got a lot of nymphs now, you may need to tighten spray intervals to five days in order to break their cycle. We’ve got a lot of data showing the effectiveness of this strategy. Hopefully, two applications would be sufficient to break the cycle.”
He says there is some concern at this point in the season about multi-pest management.
“We’re starting to pick up aphids and spider mites, and there aren’t a lot of materials available for a multi-pest spectrum. These mixes can be very expensive, and as budgets are tightening, producers are putting the brakes on their consultants’ recommendations.
“We’ve had good control of insects to this point, and I worry a bit that on the tail end of the season producers will let budgets keep them from going after pests with the best products we have and finishing this crop on out.”
Until just recently, Catchot says, “We’ve had one of the lightest aphid years we’ve seen in a long time, but we’re now seeing buildups in fields all over the state.
“We try to get the word out about the aphid fungus, but a lot of what producers get is basic word of mouth through the consultant/dealer network. Aphid numbers have really exploded in some areas recently and we have had one report of the fungus in South MS by a consultant. Timely rains the first part of the season helped keep spider mites low, Catchot says, “But now there are hardly any cotton fields where they aren’t found at some level, and we’re even seeing them in some soybean and corn fields, so producers need to stay on top of this situation.
“At this point in the season, because of the cost, I’d try and treat fields for spider mites on an as-needed basis. And I’d make decisions on a field-by-field basis, rather than blanket sprays.
“Keep in mind, too, that you can flare this pest creating a worse problem very easily with some insecticides like acephate and many of the pyrethroids — we’ve demonstrated this any number of times in our field and greenhouse work.”
Last year, Catchot says, 85 percent of the cotton that was planted in Mississippi was two-gene Bt varieties, and “this year, it’s probably 95 percent.
“We’re seeing massive bollworm egg lays across most areas — they’re everywhere in the landscape, and growers need to keep in mind that sometimes even these dual gene Bt varieties may need treatment for worms. The mixtures with pyrethroids we are recommending for plant bug control can provide something of a safety net for these worm escapes.”