Cotton Nearing Final Exam

first_imgA brave new cotton is getting mixed reviews as its first big Georgia harvestapproaches. But any critique is too early until all the cotton is picked, says aUniversity of Georgia Extension Service expert.”We still have many growers who are very happy with the product,” saidPhillip Roberts, an extension entomologist. “However, we also have some who aredispleased. But we won’t really be able to evaluate it until the harvest is in and we knowwhat kind of yields we’ve got.”The new cotton is a modern wonder. Using genetic engineering, scientists inserted agene from a bacterium, Bacillus thuringiensis, into cotton plants. This Bt geneallows the plant to produce a toxin common in nature. In a sense, the new cotton grows itsown insecticide.The toxin is deadly to tobacco budworm and helps control corn earworm, the two maininsect pests of Georgia cotton.So far, growers’ assessment of Bt cotton varies from place to place. But Roberts saidit’s not over until the cotton is picked. The harvest is Bt cotton’s final exam.”We may still have better yields with Bt cotton because of the bollworm control itprovides,” he said. “So we can’t really give it a final grade until then.”The Boll Weevil Eradication Program chased the worst cotton pest, the weevil, out ofGeorgia by 1994. “Since then, our farmers have spent more money controlling tobaccobudworm and corn earworm than all others combined,” Roberts said.The two caterpillars are both called bollworms when they attack cotton.”You really can’t distinguish between the two when they’re small,” Robertssaid. “When they’re adults, though, you can.”Bt cotton made its debut this year across the cotton belt. The seed cost growers morethan normal varieties. But they figured to come out ahead, since they wouldn’t have tospray costly insecticides to control bollworms.That hasn’t been entirely true, partly because of an oddity among bollworms.”Tobacco budworm is more susceptible to Bt than corn earworms,” Roberts said.”Normally we have a fairly even mix between the two. But this year the population isskewed heavily toward corn earworms.”No one knows what happened. “Something happened over a large area of the cottonbelt that reduced tobacco budworm populations,” Roberts said. “But we don’t knowwhat that was.”The result is that Bt cotton’s control of bollworms has disappointed some growers.”We have some Bt cotton that hasn’t been sprayed at all for bollworms,” hesaid. “In other areas, growers have had to spray once, and sometimes twice.”Statewide, Roberts said, farmers have had to spray for bollworms in about a fourth ofthe Bt cotton. “One of the things we’ve learned this year,” he said, “isthat Bt cotton isn’t immune to bollworms.”Some conventional cotton fields haven’t had to be sprayed this year. Others have beensprayed up to six times. The state average, Roberts said, is probably around three sprays.If Bt cotton does prove successful, it could add to the supply U.S. farmers grow. Butit may not affect the price of cotton products at the store.”The main benefit would be a lower cost to farmers,” Roberts said. “Thatwould give them a better profit for all the work and risk of growing cotton.”last_img