By Jodi Zirbel
Photo by Scott Tunnock, USDA Forest Service, Bugwood.orgWhat does it look like?
Among the most damaging scale insects, pine needle scale (Chionaspis pinifolia) is easily spotted for the white, shell-shaped wax cover that forms around the insect. Similar to armor, the scale surrounding a female insect measures up to 1/8 inch in length whereas males are usually smaller.
Over winter, females lay deep-red eggs, which remain protected by the scale until they hatch in mid- to late-May. Flat, tiny nymphs called crawlers emerge in spring where they seek a new feeding site and shed their red scale, resulting in a tan color. Once a new feeding site has been established, the scale quickly forms a new armor. In summer, winged males emerge to mate with wingless females. While males die quickly after mating, females continue to increase in size before laying eggs under the protection of the armor.
Host material and range
Found throughout the United States and Canada, pine needle scale feeds predominantly on the needles of pine trees, but can also target other species of conifers, including fir and spruce. Stationary for most of their lifespan, these insects are only active during the brief crawler stage where they may fall from trees, blow to nearby feeding sites, or spread by birds and animals.
The scale attaches to pine needles using hair-like mouthparts, which the insect also uses to suck plant juices. While the tree loses its nutrient supply, needles turn yellow and eventually fall off the tree. If heavy infestation continues, sparse foliage continues and twigs and branches die.
Pine needle scale is most often spread when crawlers are transferred to surrounding trees as the result of wind, or birds and animals. In addition, when mature trees touch branches, crawlers are provided an easy way to infest new conifers. Early detection and ultimate prevention will limit the extent of the infestation and damaging effects.
Among the courses of treatment to control pine needle scale is that of natural predators such as several species of lady beetles and parasitic wasps. These enemies of pine needle scale have been found feeding on eggs and newly formed scales in forest stands. If evidence of these predators is found, the use of insecticidal soap or horticultural oils can be used to help control pine needle scale without killing beetles or wasps.
Even without the detection of natural predators, horticultural oils have been found to be more effective treating pine needle scale than other scale insects. It is recommended to apply oils during the growing season to kill crawlers and eggs before the formation of new scales.
Considered the most effective treatment to eliminate pine needle scale is the use of an insecticide. Crawler sprays can be used in spring after nymphs hatch from their eggs. In addition, systemic insecticides have been found to be extremely effective against established nymphs. Among the most common formulations to treat pine needle scale are dinotefuran, imidacloprid and oxydemeton methyl.
What can you do?
Monitor trees to look for signs of infestation. Even from a distance, heavy infestations will give the tree a frosted appearance. Upon detection, the use of a spray insecticide in spring will help to eradicate crawlers, while a summer systemic application will target settled nymphs.
Jodi Zirbel is with Epic Creative, Wis. Article provided by Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about pine needle scale.