Welasco, Texas
June 27, 2005
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. |