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Yield loss to insects up slightly, so is cost of control

There was good news and bad news regarding the impact of insects on the 2005 cotton crop. The good news is that for the last five years, yield losses to insects have trended much lower. The bad news is that the cost of controlling the pests is trending upwards.

According to Michael Williams, Extension entomologist at Mississippi State University, overall yield loss to insects in 2005 was up slightly from 2004, at 4.57 percent, completing a five-year trend toward lower losses. The bollworm/budworm complex retained its ranking as the No. 1 cotton pest, reducing yields by 1.5 percent, followed by Lygus, 0.95 percent, stink bugs, 0.64 percent, thrips, 0.426 percent and spider mites, 0.35 percent. Total cost and loss for insects in 2005 were $1.264 billion. Direct management costs for arthropods were $56.51 per acre. Cost plus loss came to $88.60 per acre.

The lower losses over the past five years, “says a lot about technology, including boll weevil eradication and Bt cotton,” Williams said. “But while yield losses to insects have gone down in percentage across the Belt, we have also seen some of the costs go up slightly.”

Heliothine pests (budworm/bollworm) infested about 83 percent of the U.S. cotton crop in 2005, second only to thrips, which were found in 92 percent of the U.S. crop. Heliothine damage to the crop resulted in the loss of 520,000 bales of cotton in the United States. Oklahoma, New Mexico, North Carolina, Alabama and Texas reported losses to heliothines greater than 2 percent. California, Kansas and Virginia reported no losses to heliothines. It cost the U.S. producer about $23 an acre to manage heliothines.

Williams also noted that 95 percent of the heliothine group consisted of cotton bollworm. “We have almost eliminated tobacco budworm as a pest in cotton.”

Bt cotton acreage increased to 7.368 million acres in 2005, the survey showed. Heliothines were treated on 3.05 million acres in 2005. The cost of Bt is estimated at $9.96 per acre, representing about 17.6 percent of the cost of the arthropod management. Bt technology is used on about 52 percent of the U.S. crop.

According to Williams, Lygus is emerging as a sectionalized pest, with Lygus lineolaris infesting the Mid-South and Lygus hesperus infesting the western United States. Cost of control for this pest was $10.49 per acre in 2005. Stink bugs are also emerging as a sectionalized pest, infesting cotton east of the Mississippi River. Costs of control for stink bugs are around $5.50 per acre.

Boll weevils continue to be a factor in cotton production even though they now infest only 13 percent of the crop. Only Arkansas, Louisiana, Oklahoma and Texas reported losses due to this pest. The number of acres infested rose from last year, to 1.828 million acres. The boll weevil reduced cotton yield by 0.049 percent, but cotton producers lost only 17,000 bales to the pest. Boll weevil eradication costs for producers were $8.48 per acre in 2005.

Williams’ annual report also noted that spider mites have resurged in the last two years. Mites infested 5.23 million acres of cotton in 2005. Over 122,000 bales of cotton were lost to the pest, including 45,500 bales in California, 24,000 bales in Mississippi and 21,000 in Arkansas.

The cotton fleahopper ranked sixth in damage at 0.183 percent. Oklahoma, Texas, Arizona and Kansas reported losses to cotton fleahopper. All other states reported no loss. Fleahoppers destroyed 63,600 bales of cotton.

Aphids were ranked the seventh most damaging pest, infesting 73 percent of all cotton acreage and inflicting a yield loss of 0.13 percent. California, Texas, Oklahoma and Florida reported losses of 0.1 percent or greater. Seven states, Arkansas, Missouri, Virginia, New Mexico, North Carolina, South Carolina and Kansas, reported no losses to aphids. The pest reduced yields by 44,130 bales in 2005.

Fall armyworm took eighth place with a 0.112 percent loss and 3.28 million acres infested. Yields were reduced by 38,975 bales. Eleven states reported losses to the pest, Louisiana, Arkansas, Alabama, Mississippi, Texas, Tennessee, Florida, Oklahoma, Georgia, New Mexico and Arizona.

Four states reported infestations of silverleaf whiteflies. “This pest seems to be expanding its range eastward,” Williams said. The biggest losses were in California, Arizona and Texas.

Losses to pink bollworm rounded out the top 10. Arizona lost 1.18 percent to the pest, followed by Texas, 0.09 percent, California, 0.02 percent and New Mexico 0.001 percent.

Oklahoma reported the largest loss to insects, 13.3 percent, representing 63,900 bales of cotton. Arizona was second with 11.98 percent loss, followed by South Carolina, 8 percent, Alabama, 7.2 percent, North Carolina, 6.8 percent, California, 6.6 percent and Virginia, 5.6 percent.

All other states reported a less than 5 percent loss.

The largest number of bales lost by state was in Texas, 392,800 bales, followed by Mississippi, 168,000 bales, California, 160,000 bales and Arkansas, 132,000 bales. The biggest cost plus loss state was not surprising, Texas at $222 million, followed by Arkansas, $165 million, Mississippi, $162 million and Georgia, $102 million. p> e-mail: [email protected]

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