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Arsenal grows to battle Asian citrus psyllids in Texas

WESLACO -- Citrus growers in South Texas now have a second product to to apply using low-volume sprayers against Asian citrus psyllids, insects that spread the deadly citrus greening disease, according to a Texas AgriLife Extension Service citrus specialist in Weslaco.

(Media-Newswire.com) - WESLACO -- Citrus growers in South Texas now have a second product to to apply using low-volume sprayers against Asian citrus psyllids, insects that spread the deadly citrus greening disease, according to a Texas AgriLife Extension Service citrus specialist in Weslaco.
“A product called Danitol has recently been labeled for low-volume use in Texas,” said Dr. Julian Sauls.

The Texas Department of Agriculture’s approval to use Danitol at low-volume sprays gives growers a second option since Malathion 5 has been available at low doses for some time, Sauls said.

“Applying insecticides at low volume is very important in controlling psyllids because of their very rapid movement,” said Dr. Mamoudou Setamou, a citrus entomologist at the Texas A&M-Kingsville Citrus Center in Weslaco.

“At low volumes, a grove can be completely sprayed in a relatively short period of time, giving psyllids very little time to move out of harm’s way,” he said. “When a product is applied at high volumes, it takes a lot of time and energy, enough time for psyllids to move to another part of the grove where perhaps the effect of the insecticide has already worn off.”

Danitol also is another weapon in the effort to fend off citrus greening in Texas, also known as Huanglongbing, a bacterial disease that has devastated citrus production areas throughout the world.

Dr. John da Graca, director of the Citrus Center, said the consequences of citrus greening are disastrous.

“Many immature fruit fall off the infected trees, while remaining fruit are lopsided, remain partially green ( thus the name greening ) and taste bitter,” he said. “Symptoms spread throughout a tree which slowly declines and can eventually die.”

The disease has been devastating for the Florida citrus industry, where more than one million trees have been removed as part of the effort to control it, da Graca said. It has since been found in dooryard trees in Louisiana, Georgia and South Carolina.

Prevalent in Cuba, it has also been found in several states in Mexico.

“The Texas citrus industry in South Texas is now seriously threatened by this disease,” said Ray Prewett, president of Texas Citrus Mutual in Mission. “In fact, we’re encircled by it.”

While citrus greening has not yet been detected in Texas, there are plenty of psyllids around to spread the disease.

“Experts agree that in a place like South Texas where the psyllid is endemic, the populations can’t be eradicated. It’s never been done anywhere in the world,” Prewett said.

Buying time, he said, is one of the essential goals in fighting this disease.

“The idea is to suppress the populations of psyllids in order to buy time for researchers to come up with scientific solutions to this very debilitating disease,” he said. “The lower the psyllid populations in a recently infected area, the slower the spread of the disease.”

There is no cure for citrus greening.

“There is no treatment. Once a tree is infected, it must be destroyed to prevent it from being an inoculate for the further spread of the disease,” Prewett said.

Properly applied, Sauls said Danitol is very effective against psyllids.

“Most spraying is done at night when wind speeds are lowest, which is very important when one considers that the low-volume applicators are putting out a super-fine mist -- very, very small droplets,” he said.

The equipment used for low-volume applications is similar to that used in controlling mosquitoes but the droplet sizes are larger, Prewett said.

Setamou said many growers in the Lower Rio Grande Valley began their spray program during the trees’ dormant season, before the first flush of new growth.

“Growers who didn’t spray prior to first flush should monitor their groves for the pests and spray after petal fall, after trees have completed their bloom,” he said.

Sauls said there had been many opportunities to spray earlier this year, such as during calm winds just before and after cold frontal passages, though calm winds can’t be counted on between now and late fall.

“But those low-wind periods are something growers can look for to time their applications during late fall to winter, which are the critical times for dormant period control of overwintering psyllids,” he said.

During the rest of the season, the most likely times to spray will be limited to nighttime, he said.

“Sprays will most likely be limited to the wee, small hours of the night, but then a grower is only trying to target the couple of weeks prior to each new flush of growth: late spring ( May ), summer ( July ); and the late summer and early fall ( September ).”

Low-volume spray equipment for growers is available for loan through Texas Citrus Mutual, Prewett said.

Growers can contact John Worley for more information at 956-584-1772.