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New Mexico State University

New Mexico State University

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Spring is Best Time to Control Pinon Needle Scale

LAS CRUCES -- Spring is the best time to control a tiny insect pest on pinon trees called the pinon needle scale, said a New Mexico State University forest entomologist. The insects cause early needle drop and can severely weaken trees after several years of early defoliation.

"Each year, the generation of pinon needle scale that hatches in the springtime will attack the previous year's new growth," said Bob Cain with NMSU's Cooperative Extension Service. "So as you get larger populations on a tree, you lose an entire year's worth of growth."

Eventually, Cain said, less and less new growth will be produced because of the stress on the trees. While the trees may not die, they can weaken and become susceptible to attack by bark beetles or other insects.

Inspect pinons for black bumps on two-year-old needles. "This time of year, you can recognize infected trees by the yellow cast on the inside foliage," Cain said. "The outside needles will be green, but the needles just behind the newest growth will all be turning yellow and falling off."

Pinon needle scales begin laying eggs in southern New Mexico in February. Egg laying at higher elevations and north of Socorro usually does not begin until March or April. Greenish-yellow female scales emerge from the black waxy covering on the needles and crawl down branches to lay eggs. Tiny yellow eggs are laid in a white, cottony webbing under bark flaps, beneath branches and in the litter around the base of the trees. After about one month, the eggs will hatch and tiny crawlers will move to the ends of branches and start feeding on the needles that grew last year.

To control pinon needle scales, remove the egg masses before hatching occurs. Eggs can be washed off the trees with water from a garden hose and then raked up and discarded. Chemical insecticides or oils are effective, if timed when adult females are moving to egg-laying sites or when crawlers are hatching. For more information on controlling these insects, contact Cain at (505) 827-5833 or your local county Extension office.