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Cotton Pests Defy Control
STARKVILLE -- Don't let the name fool you, tobacco budworms love cotton. Extremely high numbers have invaded Mississippi's hill section fields at levels that defy control efforts -- seriously lessening yield potential.
Tobacco budworms are the primary pest cotton farmers must control. They feed on cotton squares and bolls (usually less than 20 days old) resulting in those bolls shedding from the plants.
These pests do not damage the leaves, so plants appear healthy at first glance.
Dr. Blake Layton, extension entomologist at Mississippi State University, said while tobacco budworms can be found statewide, the most intense pressure is in the hill counties, from the northeastern counties down to Natchez.
"Growers have experienced 50 to 70 percent control from insecticides, but with such high numbers, even 90 percent control hasn't been good enough," Layton said.
"What makes this situation worse is that yield potential was so good before the tobacco budworms hit about three weeks ago," Layton said. "Many growers spent $60 to $70 per acre trying to control this last generation of tobacco budworms and still sustained excessive yield losses. It is hard to estimate the total percentage lost."
Layton said some fields have lost 500 to 800 pounds of lint potential per acre where there may have been 700 to 1,000 pounds of lint potential.
The entomologist said in past years, he considered 5 percent boll damage heavy. This year, he has seen up to 90 percent boll damage in some fields. Tobacco budworms also hit earlier this year and in higher numbers than normal.
Some cotton growers may choose to abandon heavily infested fields and determine later if they are worth harvesting. Layton said growers make these decisions based on the number of undamaged bolls, boll maturity, insect damage potential and the stage and development of the crop.
"Some cotton fields are nearing the stage when they will be reasonably safe from insect damage. Most bolls are reasonably safe from attack at 18 to 20 days of age. Certainly, excessive numbers of tobacco budworms can and will damage bolls much older," Layton said.
Compounding the problem is the fact that subsequent generations have more resistance to insecticides and come in higher numbers. Layton said supplies of insecticides also are running low.
"Consultants and growers did an excellent job of detecting the tobacco budworms and trying to control them. They just couldn't compete against those high numbers," Layton said. "Some fields in the hills were not as damaged by high insect populations and their yield potential is good."
In Yazoo County, where 65 percent of the cotton acres are in the Delta and 35 percent are in the hills, growers are seeing a difference in tobacco budworm populations.
"Most Delta farmers have been able to maintain some control. Although no hill farmers have had 100 percent of their acreage affected, it has been a disastrous crop for some growers in the hills," said Tim Pepper, Yazoo County agent. "We don't know for sure why the insect numbers have been so much higher in the hills."
Pepper said he expects some fields to go unharvested based on the amount of insect pressure.
Dr. David Roberts, Monroe County agent, said all farmers have some fields where they may end control efforts. Some farmers are considering abandoning their total acreage. Most decisions will be made in the next few weeks as growers assess their crop's potential.
"To make matters worse, we are finding damaging levels of beet armyworms in some parts of the county," Roberts said. "Farmers have some tough decisions to make about putting more money in the fields to protect future yields."
Layton said the tobacco budworm problems are not unique to the 29 counties along the Alabama state line involved in the boll weevil eradication program.
"Tobacco budworm infestations started earlier and were more intense initially in the hill counties outside the boll weevil eradication area," Layton said.