Pine needle scale crawlers may be hatching soon

Lilac bloom is a good indicator that pine needle scale first generation is beginning to hatch and the tiny crawlers are emerging.

Pine needle scale infestation on bottom of Scots pine due to poor pesticide coverage.
Pine needle scale infestation on bottom of Scots pine due to poor pesticide coverage.

Pine needle scale, Chionaspis pinifolia, is an armored scale that can be a serious pest of Christmas trees and ornamental pines. It is often found on two-needle pines such as Scots and Mugo, but large numbers have been occasionally reported on red pine, spruce and Fraser fir. Pine needle scale feeds by sucking sap from the needles which can cause the needles to turn yellow and may reduce the trees growth.

As with other armored scales, pine needle scale overwinters in the egg stage under the hard, white covering of dead female scales. First generation eggs hatch and the tiny crawlers emerge when lilacs bloom in the spring. For those who utilize growing degree day (GDD) accumulations for timing applications, the first generation of eggs usually hatch around 250-400 GDD base 50. Research has shown that it is not necessary to apply an insecticide immediately after you see the first reddish-colored crawlers. In fact, it's best to let most of the crawlers emerge, settle down and establish feeding sites on the needles (the hyaline stage – 400-500 GDD base 50). These immature scales are exposed and have not yet secreted the white, waxy protective armor. If you apply your spray at this point and get good coverage, you should get good control. The second generation crawlers appear in July and offer another opportunity to control this scale. Remember, effective control can only be achieved with insecticide sprays aimed at the crawler stage.

Good scouting will help you assess the size of the pine needle scale population in your field and help determine the best timing for control if needed. If you see lots of scales with a round hole or a hole with jagged edges, it is evidence that parasitoids (round holes) and predators (jagged holes) have attacked the scales. Also, check to see if there are viable eggs below the hard white scale armor. Carefully flip off the white armor and see if you see the little reddish eggs. If you don’t find eggs under most scales, then you may not need to worry about spraying. If pine needle scale becomes numerous and the tree shows signs of stress, then control measures should be considered.

Growers have several options for control from horticulture oils to broad spectrum insecticides. The key is to apply these products when crawlers have emerged and to make certain you are getting good coverage. Michigan State University Extension reminds growers to be sure to read and follow all the instructions and safety precautions found on the pesticide label before using any pesticide.

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