(Dallas)—A second release of phorid flies for the control of fire ants was made this fall by Texas Cooperative Extension for Dallas County at Ray Roberts Park in nearby Denton County, said an Extension expert.
Thousands of the Pseudaction tricuspis species of phorid fly were released at the park during a two-week period from mid to late October, said Kimberely Schofield, Extension program specialist for urban integrated pest management in Tarrant County.
Ray Roberts Park, about 45 miles northwest of Dallas, was selected as the location for the release due to the likelihood the flies would be undisturbed, its proximity to a water source and an abundance of fire ants, she said.
Phorid flies, which are imported from South America, are a natural enemy of fire ants and are being used in many Texas counties for their control. Releases such as the one that recently took place at Ray Roberts Park will provide useful information on the effectiveness of phorid flies as a supplement to other forms of fire ant control, including chemical control, said Schofield.
"This is the second attempt at introducing this species as a natural control of fire ants at the park," she said. "We tried another release of the same species before in the same general area as this one. We think it was too cold when we released them, so they didn't take hold. We're hoping the conditions will be better this time and these will survive."
The phorid flies were released on all but three days during the period of Oct. 16-31, said Schofield. From 125 to 450 flies were released each time.
"They don't treat for fire ants at the park, so this will give us a good idea of what effect the phorid flies alone will have on them," she said.
Schofield will check on how the new release is progressing on a regular basis, but will not do an assessment of their actual impact on the nearby fire ant population until April 2007.
"By that time, we should know if they've taken hold and if it looks as if they're making a difference,” she said. “The fall release of these phorid flies should allow them to establish a population and have a noticeable impact on fire ants in the area by spring of next year."
Extension's release of another type of phorid fly, Pseudaction curbatus, in North Texas in 2004 has been successful, according to Schofield.
"That species took hold well and its population has spread about
four miles north and south of the release point," she said. "We're
hoping the Pseudaction tricuspis species will have similar success
in this area the second time around." 