Spider mites have always been a problem in north Alabama. Once a late-season pest, though, the mites have been showing up earlier and earlier in the season. And the rest of the cotton-growing South is taking notice.
“North Alabama has tended to get mites much more than other regions,” said Barry Freeman, Auburn University Extension entomologist. “There's no question about that. We've been watching this mite problem develop for over five years, now. I hope other areas never get as bad as north Alabama. It's alarming.”
The historic seasonal time-line of spider mites began changing in the late 1990s for what, Freeman now says, are obvious reasons. “We got away from Temik, a good miticide, at planting and moved more to seed treatments. Primarily the seed treatments involved Cruiser, although there was Gaucho too.”
After the widespread seed treatment adoption, mite problems began to intensify. “Temik controls mites while the other two don't. That was the start of a shift to more mite trouble.”
Another factor contributing to the spider mite surge was a major switch to conservation tillage. Alabama producers began planting a lot of cotton into winter fallow ground. As a result, there were plenty of winter weed hosts for spider mites. That, said Freeman, helped mites achieve field-wide distribution.
“Historically, our spider mite problems have been late-season — late July and August. Often, the problems were associated with drought. (Around 2000), we began seeing mites in June. It's progressed so much that, last year, we had spider mites killing cotyledon cotton from fencerow to fencerow. Until then, I'd never seen that.”
Those are the several other factors Freeman has come up with to explain the mite surge. “Foliar applications on seedling cotton have become common. Some are piggybacked with the first application of Roundup, there are more preventive cutworm controls. The seed treatments for thrips control are less residual than is Temik. That means the crop has needed some foliar applications for thrips control. Spider mites being an induced pest tends to exacerbate the situation.”
Freeman isn't the only entomologist who has noted such spider mite flaring. At the recent DuPont consultants meeting in Memphis, both Freeman and Roger Leonard, LSU Extension entomologist, warned about aggravating the pest.
Leonard, asked about not using organophosphates in the seedling stage for thrips, said Louisiana has seen “flaring of mites — especially from Orthene. Although Orthene is a wonderful insecticide for that window, we're very conscious of the (flaring) problem and are nervous about using it.
“When you talk about using Intruder, Centric and others, the cost of controlling thrips would be so high we don't think anyone would buy into it. In addition, if you look at the neonicotinoid labels, you're prohibited from using it within 45 days post-planting.”
With spider mites having made a move to younger cotton plants, new problems have occurred. “As we shift these mite problems from late-season to early, we're dealing with a growing plant,” said Freeman. “That complicates and aggravates control. We're treating foliage and, five days later, there's a bunch of new foliage out there. The mites are able to slip above the treated foliage.
“Dealing with mites in a growing plant is a different ballgame. For us, control after mid-July is much easier than prior to that.
When it comes to correcting a spider mite problem, Freeman's advice is to switch to a cereal cover crop where a producer is no-tilling into fallow ground.
Where mites have been a problem or threat, “I'd go back to Temik. It's the best (miticide) tool we have. Often that fact is overlooked because folks tend to think about foliar applications. I'm not a Temik salesman, but for high-risk areas it can't be beat.
“One of the main reasons is that once we get into mites, no entomologist has a good answer on how to deal with them. Mites develop resistance extremely rapidly and we don't have many good products to control them.”
While there are a few specialty products to deal with the pest, “they're expensive and farmers don't want to use them. And they aren't terribly effective. Last year, we ended up the season with Kelthane as the only good, effective compound left against spider mites.”
Unfortunately, there is a solid chance mites will become resistant to that product as well. “Absolutely, that's a possibility. Kelthane and mite resistance have a long history. The label prevents use of it over twice a year. As long as we follow those guidelines I think we'll be okay, though.”
No one should think mites can be sprayed away. It won't happen, said Freeman.
“And we can't afford to get into the field spraying three, four or five times a year either. One or two applications annually for mites are about all that's reasonable. In some drastic situations, three sprayings may be needed.”
Miticides aren't the ultimate answer, either. Producers must deal closer to the root of the problem, said Freeman.
“They need to prevent overwintering mites from being in the field and start the season with something like Temik.”
Is there anything coming down the pipe research-wise?
“Last year, we looked at Valent's Zeal. It showed good promise and some residual activity. To use it, you have to sort of catch the mites in an early building stage.
“We tested Bayer's Oberon. Personally, I'm not set on the rate but it did show promise. We need to look at it some more.”
“Acramite is another compound registered for use. I haven't tested it, but there are certainly some proponents of it.”
“Pirate is another one that needs to be studied. It's an old compound we tried to get labeled for beet armyworms years ago. That attempt wasn't successful, but it had wonderful (miticidal) properties. It's labeled for use overseas currently. I don't know if it'll be brought back to the United States.”
The problem remains “that these products are very expensive and very specialized. Kelthane, for example, isn't doing anything but taking out the mites. It isn't helping with plant bugs or anything else. So you're spending $10 per acre for six weeks of mite suppression.”
In north Alabama, there's some movement back to early-season Temik, said Freeman. “There's no question that's happening. But that isn't for spider mites exclusively. That move also points to concerns about nematodes.”
Freeman is also seeing more cereal cover crops. “That isn't a huge, dramatic shift but I'm definitely seeing more of it.”
A young consultant approached Freeman after his talk in Memphis and said, “I enjoyed your talk. I listened carefully and agreed with you.
“Now, how do I get my farmers to change from seed treatment convenience to in-furrow granular Temik?”
“I couldn't answer his question,” recalled Freeman. “Farmers' experience, I think, will have to force that move.”