With adult plant bugs migrating into cotton fields, growers need to have a plan in place to deal with them, says Angus Catchot, Extension professor of entomology and plant pathology at Mississippi State University.
“We’re getting a lot of calls about plant bugs,” he said at the joint annual meeting of the Mississippi Boll Weevil Management Corp. and the Mississippi Farm Bureau Federation’s Cotton Policy Committee. “On average they are higher than usual across the state, but numbers are much higher in the Delta region, although severity depends on location. In a couple of areas, they seem to be as bad as they’ve been in a number of years; conversely, in areas that are traditionally bad growers feel they’ve got them under control.”
With a lot of cotton now blooming and going into bloom, Catchot says, “If I can give you one piece of advice, the single best thing you can do for managing plant bugs — if you haven’t already done so — is to make an application of Diamond when your adult numbers peak during this timeframe. I can’t stress enough how much I feel this can help to keep plant bug populations in check.”
It needs to be done just ahead of nymphs showing up, he notes. “Nymphs begin appearing about the third week of squaring and numbers escalate as the crop moves into bloom. We know for a fact that Diamond is more efficacious on first and second instar plant bugs. When we get that first application out and they’re hatching into it, they’re at their most susceptible stage.
“We also know that, as an insect growth regulator, Diamond has no activity on adults. But we do have research showing that when an adult female is exposed to it, she lays significantly fewer eggs, and of the eggs that are laid, significantly fewer of them hatch. I think this application is the most important thing you can do to control plant bugs in our area.”
However, it may not fit all situations in hill areas, Catchot says. “In some hill locations, we’re seeing some higher plant bug levels than in several years. I wouldn’t necessarily suggest applying it on every acre, but would let pressure in a field dictate whether or not to apply Diamond.”
The EPA has approved a full Section 3 label for Transform this season, he notes, “and quite a bit has already gone out — which is somewhat surprising, given its premium cost.
“I’ve been working with this material about six years, and I really feel it’s probably as good as our best top tier products, sometimes better. But I’ve had quite a few calls about its performance. I think growers, because of its high cost, are expecting to get more from it than it can actually deliver. You’re not going to be able to spray it and keep adults from moving into the field, particularly prior to bloom, and you’re not going to get two weeks’ residual under heavy pressure.
“But don’t assume that you have control failure with these heavy adult populations that are moving into some of our fields. If you spray one week, then come back the next week and the numbers are as high or higher, it doesn’t mean you have control failure — you’re just continuing to get movement into the field.
“The only way I feel you can evaluate how your insecticide is performing against adult plant bugs is to look at square retention. You may have plant bug numbers this week double what they were the previous week, but if you’re retaining squares, the product is working — you just have a steady influx of insects into the field. Please keep this in mind.
“I do think you need to use Transform,” Catchot says. “It’s a completely different mode of action — and it’s also fantastic on aphids.”
Growers in many areas of the state have started to spray for spider mites, he says. “I’ve had some calls that they’re showing up in corn also. If you’re going to apply an abamectin-based product, which is by far the cheapest material, be aware that in the past couple of years we’ve begun to see some decline in efficacy of these products, particularly toward the tail-end of season. In some areas, it hasn’t performed as it once did, even at twice the rate.
“I would recommend that you apply not less than 10 ounces out of the gate, and it still will be cheaper than the alternatives. That’s better than starting with a lower rate and then having the cost of coming right behind with another application.
“If it doesn’t work, please do not follow with that same product. Instead, use a different chemistry. Several are available: Portal, Oberon , and Zeal are fantastic miticides, and I feel we need to begin rotating these into our mite control programs.”