The number of plant bugs inhabiting Mid-South cotton fields went from absolutely none early in the 2001 season to billions and billions by the time growers were readying for harvest, according to a group of entomologists attending a recent meeting on the pest.
The research meeting, held at the USDA research complex in Stoneville, Miss., served as an opportunity for researchers and crop consultants to brainstorm some solutions to the major challenges cotton growers experienced with the tarnished plant bug in 2001.
“This is one of those unusually high plant bug years, but part of the problem could be the void left from other pests, due to the eradication program and the planting of Bt cotton,” said entomologist Blake Layton with Mississippi State University in Starkville, Miss.
Herbert Jones, a crop consultant in Leland, Miss., said, “We fought plant bugs all year.”
Due to the current economic situation, he said, growers were forced to try to cut costs by reducing herbicide applications. As a result, the weed hosts available to plant bugs were plentiful. “Then the rainfall came, the cotton began to rot, and the question became, ‘How much can you afford to put into it to protect the top crop?’” Jones said.
Economist Fred Cooke at the Delta Research and Extension Center in Stoneville, Miss., said, “The price of cotton is finally influencing every aspect of production.”
Ronnie Bibb, a consultant from Cleveland, Miss., agreed that low cotton prices were at least partly to blame for the high numbers of plant bugs growers found in their fields in 2001.
“I've been checking cotton since I was 14 years old and 2001 was the worst plant bug year I have seen in my life,” Bibb said. “What caused the problem was money. You had farmers that were trying to control plant bugs surrounded by insurance farmers with an infinite number of host plants.”
According to USDA entomologist Dick Hardee, plant bug numbers started low early in the 2001 season, but because growers weren't able to put a lot of extra money into the crop, the resulting weedy fields provided an abundance of host plants for plant bugs to reproduce and thrive.
The same scenario played out across the Mid-South, with growers in Mississippi, Louisiana and Arkansas all reporting high numbers of tarnished plant bugs infesting their cotton fields.
In Louisiana, entomologist Gene Burris said growers in his state had much higher than normal numbers of plant bugs in 2001. “We were really surprised very early in the season by the high numbers of plant bugs. We had tremendous amounts of adults moving into the borders of fields,” he said. “The farther south you went, the more problems growers had controlling infestations.”
Arkansas Extension entomologist Gus Lorenz, too, said the farther south in the state you went, the higher the populations of tarnished plant bugs. “Overall, it was as heavy a plant bug population as we have ever seen,” he said.
Late-season sweep counts in many south Arkansas fields yielded five to six plant bugs per foot of row, according to Lorenz. Even with the high numbers, most growers were able to obtain adequate short-term plant bug control with insecticide treatments. Within five to seven days after an insecticide application was made, however, the treated field was re-infested with the pest.
What works and what doesn't
Mississippi Delta cotton growers, on average, sprayed 3.6 times for plant bugs in 2001, according to Layton.
Bibb said his growers treated for plant bugs anywhere from a low of four times to a high of seven times during the 2001 growing season. Control treatment expenses ranged from $3 per acre to $8 per acre, plus aerial application costs.
“My numbers were about the same and some areas needed eight or 10 insecticide treatments to control the plant bugs, but the growers couldn't afford to spend that money,” said Jones.
Despite the release of new insecticide products each year, cotton growers' insecticide of choice for plant bug control is most often Orthene or Bidrin.
Burris said, “A lot of Orthene and Bidrin went out in Louisiana this year. Beginning early in the season, control treatments using these two insecticides were made every 10 days to two weeks.”
Research by USDA entomologist Gordon Snodgrass hasn't shown any significant plant bug resistant to the insecticides Orthene, Bidrin and Vydate.
However, he calls pyrethroid applications made for the control of plant bugs in the Mississippi Delta a “crap shoot. You may be able to get away with one pyrethroid application per season, but that's about it.”
Scott Stewart, an entomologist at Mississippi State University in Starkville, Miss., said, “It's amazing what a difference 100 miles makes, because in my area pyrethroids are the material of choice for plant bug control. Over in the Delta, however, that is not the case.”
Plant bug resistance to malathion is also growing rapidly, Snodgrass said. “I have seen up to a 30-fold resistance to malathion buildup through the fall, but for the most part that level seems to drop by spring planting time.”
Which insecticide treatments will the entomology experts recommend to cotton producers in 2002?
Even if money weren't an object, Snodgrass said, he would still recommend Orthene for the control of the tarnished plant bug in cotton. LSU AgCenter entomologist Roger Leonard also relies on Orthene as the “standard” for plant bug control.
What may throw a kink in that plan is a recently announced label change for Orthene and its generic acephate counterparts.
Beginning in 2002, it will be illegal to apply Orthene by air at a rate greater than 0.75 pound per acre, according to Frank Carey with Valent. Before the change, an application of 1.0 pound of Orthene per acre was a standard insect control recommendation.
In addition, Extension entomologists in Louisiana and Mississippi said they will probably add the insecticide Centric, at a rate of 3 ounces per acre, to their 2002 list of recommended plant bug control products. In Arkansas, Centric will likely be recommended to growers at a rate of 2 ounces per acre.
“We need to consider the use of all possibilities, because, in the future, we are going to have to use every weapon at our disposal to control these pests,” adds USDA geneticist Bill Meredith.