Texas farmers are urged to be on the lookout for a new and highly destructive whitefly that's resistant to many insecticides now being used.

Dr. T-X Liu, a Texas Agricultural Experiment Station vegetable entomologist in Weslaco, said the new pest is not indestructible, but a change in management strategies will be required if and when it is detected here.

Known as Biotype Q, the sweet potato whitefly (Bemisia tabaci) Biotype Q has been detected in small numbers in California and Arizona but may have been transported aboard plants to other southern states, including Texas.
Scientists in Arizona and California who made the discoveries in March said the insect is thought to have originated in the Mediterranean region. It has a host range of more than 500 plants from 74 families, including vegetables and ornamentals. Like other whiteflies, this insect can damage many other crops, including cotton, unless controlled.

"The Biotype Q is highly resistant to the insecticides and cultural practices that have helped us manage the silverleaf whitefly, or Biotype B whitefly, in Texas and the Rio Grande Valley for many years," Liu said.

An outbreak of Biotype B whitefly here in the early 1990s made it one of the most important pests on cotton, vegetables and ornamentals. About a decade later, new insecticides and coordinated cultural practices reduced populations.

The Biotype Q whitefly reproduces and develops more rapidly than the Biotype B, is capable of transmitting more viral diseases, and has a wider range of host plants, Liu said.

It also looks identical to the Biotype B and can be detected only by analyzing the esterases (enzymes), protein or DNA of the whiteflies.

Liu, U.S. Department of Agriculture personnel and Experiment Station scientists regularly trap whitefly samples and send them to the University of Arizona for identification.

"We're asking growers to report any unusual whitefly activity in their fields or greenhouses," Liu said. "This would include a sudden, large increase in the number of whiteflies, or a sudden whitefly resistance to insecticides that had been effective. Whiteflies are less of a problem in north Texas fields, but greenhouse operators there should also be on the lookout."

Dr. Scott Ludwig, Texas Cooperative Extension Integrated Pest Management specialist for at Overton, said the threat of Biotype Q and the trend toward increased insecticide tolerance of Biotype B should encourage greenhouse growers to improve their overall whitefly management practices.

"If after growers have implemented the proper insecticide rotations and they still see an increase of whitefly activity, they should contact us," he said.

Early detection of Biotype Q whiteflies would help manage populations before they spread and alert growers to new management strategies, including the use of new insecticides.

"We could also get a jump-start on applying for state and federal funds for research and the implementation of new technologies," he said.

Liu and Ludwig are part of a technical advisory committee of entomologists from several states who meet electronically to keep each other informed of the latest news on Biotype Q.

"Now more than ever it's important that growers maintain their scouting activities, good cultural practices and insecticide rotations. And if they see anything unusual in whitefly activity, please report it immediately to a Texas Cooperative Extension county agent," Liu said.