The “selective” insecticides now entering the cotton market offer new opportunities for growers, scouts and consultants. But more expertise will be required to use these products effectively and profitably, says Phillip Roberts, University of Georgia Extension entomologist.
“Selective chemistry requires more expertise, especially when deciding how the use of a product will affect the ‘big picture’ of cotton production,” says Roberts.
In recent years, several new insecticides have been introduced for cotton, he says. “We have new labels and several experimental insecticides that are currently under development by industry. Most of the chemistry being brought to the marketplace is very selective — it's specific to a group of insects or even individual insects. Also, these products are more expensive than our traditional pyrethroids,” he says.
These new insecticides, he adds, have a “safe” environmental profile — a requirement before a new product to be brought to market.
Before discussing the new chemistry, Roberts says there still are several “non-insecticide” tools available to cotton producers.
“One of these is an egg identification kit. In certain areas of Georgia, it has become very important that we know which species are in the field. For example, we need to know if its corn earworm or tobacco budworm. We can get a good idea by looking at moths as we scout the fields. But these egg identification kits give us much better data,” says the entomologist.
Opportunity for improvement
Integrated pest management — or IPM — also offers many opportunities for improved insect control, says Roberts. “IPM is simple. It's just using all available control tactics, and putting them together so we can produce cotton as efficiently as possible. I like to look at IPM as being ‘informed pest management,’ or even ‘innovative pest management,’” he says.
Georgia growers have been fortunate in recent years that they haven't had to treat for heavy insect pressure, he says. “But making the decision to treat and knowing which product to use actually has become more difficult. The ‘easy out’ is to just spray a field. Knowing when to hold back is much more difficult.”
Cotton production in Georgia has been made easier by the elimination of the boll weevil, notes Roberts.
“It is vitally important that we remain free of boll weevils. This past year, we had one small re-infestation of weevils in Dooly County. But only about 200 acres were treated, and that's very good. We've never gone an entire year without catching a boll weevil in Georgia. I would encourage growers to do everything possible to prevent bringing weevils into the state, including not bringing machinery in from infested areas.”
Several new products have been introduced recently for use in cotton insect control, says Roberts. They include Confirm, Intrepid and Steward.
“Confirm and Intrepid are sister products — they're both insect growth regulators. These products have very minimal impact on predators and parasites. They are very safe compounds for users, with a re-entry interval of only four hours. These are safe, selective compounds — the type we will continue to see being brought to market.”
Confirm has been available for beet armyworm control under a Section 18 in Georgia since the mid-1990s, he says. “It's a good product for beet armyworms. It has a long residual action, and it's a slow-acting product. It's also labeled for fall armyworms, but that's a difficult pest to control, and we still need to do some work in that area.”
Intrepid, which was labeled this past October, is very similar to Confirm, says Roberts. “It has a broad spectrum of activity over various caterpillar pests. It is labeled for beet armyworms, fall armyworms, soybean loopers, tobacco budworms and corn earworms. We'll be looking at using this product on the armyworm complex and loopers. At the rates needed for controlling tobacco budworms, it'll probably be too expensive to use this product.”
Steward is a very selective product, he says, and is specific to caterpillar pests. It has a very small impact on predators and parasites.
“The mode of action of this product is somewhat similar to a pyrethroid, yet it is different, so there's no cross resistance. If you have pyrethroid-resistant tobacco budworms, Steward would offer control of that population just as it would on a susceptible population. It is a new mode of action offering broad-spectrum caterpillar control.
“It has minimal impact on big-eyed bugs and minute pirate bugs, but it does have activity on plant bugs. I wouldn't consider this a clean-up type treatment for major plant bug problems. There is some activity on stink bugs, but it's not the level of activity needed to control the pests. We'll learn more about this product as we get into larger fields this year.”
The primary way for an insect to be affected by Steward is through ingestion, says Roberts. This puts a premium on coverage, he adds.
“Coverage will be very important. It's not a cleanup treatment. These new products aren't like pyrethroids — you can't go into a field and kill large worms. You must use these products correctly, and they must be targeted against small worms if they are be successful.”
Selective insecticides, he says, give growers the opportunity to preserve beneficials and to avoid flare-ups from other insect pests like aphids or beet armyworms.
Growers must consider several factors when they incorporate selective insecticides into their management programs, notes Roberts. “In some situations, we'll have to deal with multiple pests, and we must think about the economics. This new technology will offer a lot of opportunities, but it'll require more expertise to get the most returns from these products.
“We must continue to think about resistance management. It's critical to maintain the efficacy of pyrethroids on corn earworms. In areas, we now have multiple modes of action for tobacco budworms and corn earworms. We have an opportunity to truly practice resistance management in rotating this chemistry.”
Roberts advises growers not to treat successive generations of insect pests with the same chemistry. “We have a generation of tobacco budworms every 30 days. We must position different products so that we can rotate them. The bottom line is that we need to fit these products into the system so we'll get the most return.”
Scouts and consultants become even more important with the advent of selective chemistry, he says. “The best money you'll spend for insect control will be whatever you spend to hire a good scout or consultant. As we move toward selective chemistry, expertise becomes even more important. Pest management is more than just scouting — it's making difficult decisions.”