Voracious Insect Threatens Pinyons

Foresters seek help fighting renewed infestation of leaf-gobbling scale pests

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Photos courtesy of Gila County

Foresters warn that pinyon pines like this one now harbor white masses of scale eggs, which will cause infestation if not removed soon.

Foresters are appealing to Rim Country residents to help head off an infestation of an insect that can chew all the leaves off struggling pinyon pines, leading to the eventual deaths of even large trees.

Infestations of native pinyon needle scale have already been reported in the Payson area. Although two relatively wet winters have renewed the defenses of trees in the region, foresters still worry about the return of assorted insect pests that could cause a resumption in the large-scale die-off of thousands of trees.

The pinyon need scale infested an area in southeast Payson and Beaver Valley Estates north of Payson in 2007.

In 2008, yet another infested area was discovered in Round Valley south of Payson. A smaller pocket was also noted on the west side of town in the Trailwood subdivision.

It is important that homeowners in these areas examine their pinyons for this insect and treat them appropriately. The insect can kill individual trees over a period of time due to the annual loss of needles.

Due to the recent warm weather, female scales have already emerged from their over-wintering stage on the needles in these areas. Very noticeable clusters of yellow eggs held together in loose, white, cottony webbing have been laid by the females mainly in branch crotches, along the underside of branches, on the trunk, and at the base of the tree. The females die shortly after laying eggs.

Heavily infested pinyons can be easily detected by the yellow or orange discoloration of the older needles towards the back of the branch. The needles are covered with small, black, bean-shaped scales that pierce the foliage and remove the sap, causing the needles to discolor, dry and fall off. Small trees may be killed within a few years, whereas, larger trees may lose one or more branches and may take years to die.

The trees most likely to die from the annual defoliation by the insect are pinyons growing on drier, rocky outcrops, south- and west-facing slopes and transitional zones between pinyon-juniper and grassland vegetation types.

Pest control experts recommend a variety of steps to save infested trees, including:

• Wash the eggs off branches and trunk with a garden hose equipped with a high pressure nozzle, then allow eggs and litter one to two days to dry.

• Rake eggs, litter and debris out from under the tree.

• Dispose of the eggs in plastic garbage bags. Raking may not be practical if heavy brush, rocks or other material is present under the tree. However, washing the eggs off the tree is still recommended.

• Removal of the eggs from infested trees will be simplified if property owners have already treated vegetation for fire prevention reasons.

Unfortunately, repeated washings may be necessary since not all eggs will be laid at once. It’s critical to wash away the eggs before they hatch, since the young scales (crawlers) will move quickly to the needles, where they can only be be treated with insecticides.

Egg hatch usually occurs in May, providing property owners with time for egg removal — but the sooner the better.

Unless there are local water restrictions, consider slow, deep and infrequent watering of infested pinyons nearest the home, starting as soon as soils dry out, with a soaker hose placed around the drip line of the tree. Continue until monsoon rains start.

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