Pinyon needle scale, an insect that feeds on the sap in the tree's needles, have infested the pines in southwest Payson.
As they literally suck the life out of their host trees, the pinyons slowly die by defoliation.
"Drought conditions Payson experienced last winter may have triggered the spread, but that is speculation on my part," said Arizona forest health specialist Bob Celaya.
Scale-infested pinyons were first identified in Round Valley in 1986.
Pinyon needle scales, known by their scientific name, matsucoccus acalyptus, are .5mm in size.
Wingless females emerge from scale coverings on the bark of the tree in April to mate with male insects that have wintered in webs beneath the trees.
After mating, the female lays visible eggs. Four to five-and-a-half weeks later, the nymphs hatch and crawl to the tree's upper foliage to feed. Once they start to eat, they cover their bodies with a waxy coating that safeguards them against the environment, predators and contact insecticides.
"Removal of the eggs from your pinyons will be simplified if you have already treated your vegetation for fire prevention (by thinning and pruning)," Celaya said. "If you have pinyons infected with needle scale, you can basically walk right up to the tree and see the egg masses. Of course, if you haven't pruned, it will be hard to get to the egg masses on those trees."
Ways to detect scale-infested pinyons:
- Clusters of yellow eggs held together in loose, white, cottony webbing in branch crotches, the underside of large branches and the base of the trunk.
- Yellow-orange discoloration of needles toward the back of the branch.
- Needles covered with small, black, bean-shaped scales.
Control of the scale at this egg stage of the insect is a three-part process. First, wash the eggs off branches and trunk with a garden hose, equipped with a high-pressure nozzle, then allow the eggs on the ground one or two days to dry.
Next, rake the eggs out from under the tree. Then, dispose of the eggs in plastic garbage bags.
Although the Town of Payson restricts residents from watering native tress, the water department is not opposed to the initial strategy of washing the eggs off, raking them up and disposing of them.
However, a Town of Payson ordinance forbids watering of native trees and repeated washings may be necessary as the scale insect does not lay all her eggs at once.
Residents who have an infested pinyon tree should call the water department at (928) 474-5242, ext. 4.
"If you really feel you need to water this tree extensively, give us a call and we will come and help you make a decision," said Payson Public Works Director Buzz Walker.
There are contact chemicals, such as malathion and horticultural oil, that may be used on the scale in the crawler stage.
Pinyon pine nuts should not be harvested from trees that have been treated with insecticides.
"I would rather people take this one step at a time," Celaya said. "Next month, when the eggs hatch, will be the time to use an insecticide. For now, I would like to get people to remove the egg nests from the trees."
Scales have spread widely in Prescott over the past 30 years.
"I don't know what is going to happen in Payson," Celaya said.