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Freakish insect invasions plague Mid-South farmers

There's a road in Prairie County, Arkansas that's almost too slick to drive on. But neither rain nor sleet nor black oil spill has infested the roadway. It's, ugh, caterpillar guts.

This year, almost every farmer in the Delta has heard a horror story or two of a freakish insect invasion. None is weirder than that told by Arkansas Extension plant pathologist Rick Cartwright.

Cartwright says that saltmarsh caterpillars were so bad in Prairie County that a farmer used a roller to crush worms crawling across a road between fields, causing a slick road surface. He said in Clay County a road became slick where vehicles were running over worms.

Saltmarsh caterpillars, grasshoppers, sugar cane beetles and armyworms are a few of the pests showing up in high numbers in Mid-South fields, entomologists report.

Mike Williams, Extension entomologist at Mississippi State University in Starkville, Miss., describes this year's insect situation as “weirder and weirder.”

The likely reason for the unusually high insect pressure, he says, is the weather. “Weather patterns are the major factor in pest development. In fact, weather conditions determine about 99 percent of our insect populations this time of year. If we could ever understand the weather patterns we could be a lot better at predicting insect populations.”

While many Deltans expected the cold winter temperatures to, at the very least, lessen the number of pests making their home here this spring, Williams says that isn't always the way it works. If spring comes on warm and early, it gives insects time to build large populations on alternate hosts. That, he says, is the case this year.

“This has really been a different kind of year,” he says. “Things have started off a little weirdly. We have a lot of pests like saltmarsh caterpillars and grasshoppers, that we have every year, but are being found in unusually high, damaging numbers this year.”

Williams says he is receiving a higher number of calls than usual reporting saltmarsh caterpillar infestations in soybeans and cotton. He's also received reports of early season armyworm damage in rice fields. In addition, the reports of crop damage by bean leaf beetles and thrips are increasing.

“Because of the dry weather a lot of the alternative, or main, host plants for pests are drying up and the insects are moving to what's green — and that's neighboring crops,” he says. “The recent rains moving across the area should kick both soybeans and cotton in the butt, making the crops less susceptible to these early season insects.”

One bright spot of 2001, Williams says, is the documented ten-fold reduction in boll weevil trap counts over last year. “We are catching a few weevils in traps, but the overall reduction in weevil numbers is a testament to the success of the eradication program.”

Ralph Bagwell, entomologist at the Scott Research and Extension Center in Winnsboro, La., says growers in his state are facing a menagerie of early season insects.

“We've had a lot of what I call trash insects due to late burndown treatments. Because the cotton emerged almost immediately after the weeds died off, a lot of those insects feeding on the weeds in the fields moved onto the cotton and started feeding on it.”

Quite a lot of treatments have gone out for early season insects, according to Bagwell. “The problem is that there's no single magic bullet available that will control every pest out there,” he says.

Like its neighboring states, Louisiana is being overrun in some areas by the sometimes difficult to control saltmarsh caterpillars that are migrating from wheat into neighboring cotton and soybean fields.

In addition, farmers in Louisiana are reporting heavy infestations of thrips in cotton. “The difficulty there is even if you had a systemic insecticide out at planting, you may still seeing a lot of feeding injury. The early treatment is causing the thrips to die after feeding, but not before they damage the cotton plant,” Bagwell says.

Insect pressure is also heavy in Mississippi, primarily due to warm early spring temperatures, according to area Extension agent Tommy Baird in Indianola, Miss.

“We're usually seeing second generation insects in crop fields by about the first of June. This year, we were probably already into the second generation of insects by the middle of April,” he says. “The early temperature warm-up may have sped up the insects' reproduction cycles, which produced a second generation of insects a little earlier and a little heavier than usual.”

While farmers across the state are reporting higher populations of almost every type of insect, Baird says populations of armyworms and saltmarsh caterpillars are especially high. In one instance, he says, a grower was forced to replant 200 acres of milo due to armyworm damage.

“Farmers can expect higher populations of most everything we deal with,” Baird says. “We're going to continue to have insect problems until we have a couple of winters in a row with extremely cold temperatures. The ground is going to have to freeze at least six- to eight-inches deep each year for several years.”

Arkansas' Cartwright said farmers have been using insecticide rates lower than Extension recommends for heavy infestations of early season insects and haven't gotten good control. He said some farmers have had to re-treat fields.

“Farmers have had a difficult time finding methyl parathion, which is probably one of the better insecticides. Supplies seem to be low, and some people don't have the proper license to purchase it and get it to farmers.”

One of the worst armyworm infestations in many years has wheat farmers scrambling to buy insecticides, according to William Johnson, wheat specialist with the Cooperative Extension Service, University of Arkansas. So far, farmers have sprayed about 60 to 65 percent of the state's 1.1 million-acre wheat crop.

If left unchecked, armyworms can decimate wheat, cutting off the heads containing grain. “The treatment level is about five or six armyworms per square foot,” Johnson said. “We're seeing 60 to 70 per square foot. The ground just moves because there are so many worms.”

Johnson said entomologists had hoped cold weather in December would reduce the pest's numbers. However, the ground apparently didn't freeze deeply enough to hurt armyworms in their overwintering stage.

The explosion of armyworms was not unexpected. Armyworm numbers have been building up in Arkansas over the past two or three years.

Insecticide treatments are a cost that wheat farmers don't need. Johnson said the demand for wheat is poor and the market price is disappointing, about $2.50 a bushel. “There's really no profit in wheat this year,” he said.

Some worms have been dying of disease, and Extension experts expect a decline in worm populations soon if the trend continues.

Meanwhile, Johnson is estimating that the statewide average wheat yield will be about 50 to 52 bushels an acre, compared to last year's state record average of 56 bushels.

The sugar cane beetle has caused serious damage to corn in Tennessee in several counties. Corn planted into sod or old pastures suffer the most damage. In Fayette county, one producer suffered a loss of 40 percent plus in stand.

The beetle operates just below the soil surface eating into the sides of corn plants. The plants first symptoms show dying of the center leaves then fall over and dry up.

Lawrence, Dyer and Fayette counties report damage from the pest. The beetle is black in color with strong legs and coarse spines adapted for digging. The back of the beetle has numerous pits or punctures. The larvae are C-Shaped white grubs and dirty white in color.

There are also reports of heavy grasshopper infestations in west Tennessee.

Armyworms are on the march across much of southern Missouri. “It looks like a million of them when they cross the blacktop highway,” said Dwight Holmes, Extension small farm educational assistant at Alton, Mo., near the Arkansas border in south central Missouri.

“It's the worst I've ever seen. Pastures have been eaten to bare ground in some locations forcing cattle owners to sell their herds.”

Tom Hansen, regional extension agronomist at Springfield, Mo., said the armyworms are moving from fescue hayfields, after eating all of the vegetation, into nearby cornfields. “They eat everything, right down into the ground. There's nothing left to come back,” Hansen said.

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