Second generation pine needle scale has begun to hatch

Jill O'Donnell, Michigan State University Extension, and Howard Russell, MSU Diagnostic Services - July 24, 2015

Pine needle scale summer generation has begun to hatch in Lower Michigan. Target insecticide applications for when most crawlers have emerged and begun to settle down.

Pine needle scale may go unnoticed until second generation crawlers move to the new growth and secrete white, waxy covering in fall. When populations are heavy, trees may become un-harvestable.

Pine needle scale, Chionaspis pinifolia (Diasoididae), is an armored scale that can be a serious pest of two-needle pines used as Christmas trees and ornamental plantings, especially Scots and Mugo pine. Pine needle scale feeds by sucking sap from the needles, which can cause needles to turn yellow and may reduce the tree’s growth. In Michigan, we see two generations each year. The first generation crawlers emerge in spring about the time of full lilac bloom. Second generation crawlers normally occur in mid-July at about 1,280-1,500 growing degree days (GDD) base 50. It is this generation of newly hatched crawlers that move onto new growth, or current-year needles.

The summer generation eggs hatch over a relatively long time period of two to four weeks. This extended period of hatching probably occurs because spring generation scales develop at different rates, depending on where they are located on the tree. Some scales develop relatively quickly because they are exposed to more sun and warmer temperatures than scales that feed in shaded locations on the tree. As a result, eggs that develop into second generation adults are laid over a longer period of time as first generation adult female scales reach maturity.

Second generation scales mature and lay eggs late summer then die. Their eggs overwinter under the white scale covering until the following spring. Often, it’s not until fall when the scale develops this white, wax covering that growers realize they have a problem.

With this summer generation, growers will want to target their insecticide applications when most of the crawlers have emerged and begun to settle down. With the longer hatching period, two applications may be needed.

For more information on pine needle scale, see “Biology and Management of Pine Needle Scale” by Michigan State University Extension.

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