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New Mexico State University

New Mexico State University

News Center

Georgia and Arkansas Wasps May Help Control New Mexico's Pine Tip Moth

LOS LUNAS - A wasp the size of a pinhead may help New Mexico homeowners and foresters control pine tip moth, a virulent pest that's maiming pine trees around the state.

Mike English, an entomologist and superintendent of NMSU's Agricultural Science Center at Los Lunas, examines pine tip moth damage on a Scotch pine at the science center. The tree is about 10 years old and should be two to three times taller, but the moth has stunted its growth. (09/04/2002) (NMSU Agricultural Communications Photo by J. Victor Espinoza)

The wasp, which entomologists at New Mexico State University's Agricultural Science Center at Los Lunas imported this summer from Georgia and Arkansas, is a natural predator of the pine tip moth. Researchers released the wasp on a variety of pine trees at the center to see if the wasp can establish itself under local conditions, and to test its effectiveness in controlling moth populations.

"We generally use insecticides to control pine tip moth infestations, but we want to replace pesticides with biological controls," said Mike English, an entomologist and center superintendent. "We imported some natural predators from Georgia and Arkansas that have been very effective in those states. We hope to get the wasps established here and then introduce them around New Mexico."

Pine tip moths, a particularly widespread problem in the Southeast, apparently rode into New Mexico in the late 1970s aboard imported Afghan pines, said Bob Cain, a forest entomologist who helped start the research project at Los Lunas. The moths originally established themselves in areas around Las Cruces and Roswell, but they've since spread throughout most of the south, the mid-Rio Grande Valley and as far north as Santa Fe and Espaņola.

"Initially, the moths fed on Afghan pines, then they moved onto Austrian, Scotch, Ponderosa, Mugho and Japanese Black pines," Cain said. "Now they're a real problem for most two- and three-needle ornamental pines, with the exception of piņon."

Moth larvae reduce tree growth by mining tree buds and shoots, English said. They lay their eggs at the base of shoots, which then hatch into worms that bore into the shoots and kill them.

"They attack the tree's growing point at the tip of the shoot," English said. "They eat right through it, hollowing out the middle until the shoot dies."

The feeding larvae stunt tree growth, forcing pines into a low-rounded or mushroom shape, rather than the natural cone shape, he said.

"It doesn't kill the tree, but it looks terrible," English said. "We've got pine trees at the center that are 10 to 12 years old, but only 3 or 4 feet tall because of the moth."

The problem is particularly widespread in urban and suburban areas, where a broad variety of pines grow. "It's like a great big chef salad out there for these critters," English said. "They can pick and choose what they want to eat."

The moths have 2 generations per year, Cain said. They pupate inside the tree shoots, where they overwinter.

Once pines reach 6 to 7 feet, the moths are less of a problem, but to get the pines established, growers need to spray trees regularly with insecticides, Cain said.

To reduce pesticide use, Cain and English turned to the University of Georgia, where researchers have collected large populations of predator wasps that feed exclusively on pine tip moths. The wasps deposit their eggs on top of pine tip moth larvae. When the wasps hatch, they feed on the moth larvae, Cain said.

In June and July, the Los Lunas center received six wasp shipments from Georgia and Arkansas, releasing about 100 wasps on pines infested by moth larvae. Researchers covered the targeted trees with netting to keep the wasps in and fed them a mixture of honey and beer, English said.

"We'll see next spring if they got established," he said. "It's a shot in the dark because we have different climatic conditions than Georgia and Arkansas."

If the wasps get established and reduce moth populations, NMSU will import more and breed them at Los Lunas, setting up an insectary to introduce the wasps around New Mexico, Cain said.

If the wasps do become established, homeowners need not worry about getting stung, English said. "Their stingers are too small to penetrate human skin," he said. "It would be like a Chihuahua trying to bite your leg off."