Scale insects are tiny, tiny insects that protect themselves by secreting a waxy coating that resembles a reptile or fish scale. These herbivores are immobile under their shell and feed on trees and shrubs by “sucking” out the sap through their specialized mouth parts. They start life as an egg, which has overwintered inside of their mother’s scaly home. The potential pests then hatch, exit the scale, and are able to crawl around the host plant as a “crawler”. Often, scale insects are blown around to surrounding vegetation during this crawler stage. The crawler stage is the best time to treat these insects as they are not protected by their scale.
Once settled, females insert their mouth parts into the plant, lose their legs, and start to feed. They either mate with males who have retained their wings and legs or females reproduce without mating (process called parthenogenesis). During the mating and egg lying period, the female produces its waxy scale and lays its eggs under its protection. The female will generally die through the winter, but her brood lives, overwintering as eggs to hatch and form crawlers in the spring.
Scale insects are a huge problem in ornamental trees and shrubs. Their numbers build and spread rapidly, introducing populations to new areas and new ornamental species. Timed applications are able to dispatch these foes, but their persistence in our landscape ecosystems will require continued monitoring and control.
Damage of scale insect can include browning of leaves or needles shoot and branch death. Eventually populations can reach a high enough level to severely weaken the planting, opening up opportunities for secondary pests which may cause mortality.
Another byproduct of scale insects is honeydew or sugary waste excreted by the bug. Fungi feed on the honeydew and cover a plant with a black, blotchy, sooty mold, which reduces the surface area available to receive light. This further weakens the tree or shrub, possibly influencing secondary problems that are usually shrugged off by a healthier plant.
One such scale insect, Chionaspis pinifoliae, or Pine Needle Scale is one of the most serious pests of ornamental pines in the United States. They can cause significant needle deterioration and needle loss in Japanese black pine and other ornamental pine species. Scale, combined with secondary infections of fungi or infestations of opportunist insects can eventually contribute to the death of a planting.
If you are unsure if you have a scale problem on your landscape or would like to learn more about what you can do to preserve your trees and shrubs, please have our arborist out to do a complimentary inspection of your property. Not all pest populations need treatment!
Johnson, Warren T., and Howard H. Lyon. Insects That Feed on Trees and Shrubs: An Illustrated Practical Guide. Ithaca, NY: Comstock Pub. Associates, 1976. Print.