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The Lecanium Scale insect is common on many types of trees and is prevalent on fruit trees. The appearance of Lecanium scale is dark crusty bumps, thick, white waxy bumps, or clusters of scaly bumps on stems and the undersides of leaves. The bumps can often be scraped off with a dull knife, and the underside of the bumps is normally a softer material. When a tree is infected with Lecanium scale, it is very common to see a shiny, sticky substance on the leaves. This material is called honeydew and is an undigested sugar substance that is secreted by the scale insect. In certain climates, the honeydew becomes a prime-growing medium for black, sooty mold.
Lecanium scale lay their eggs on the woody material of the tree. In the spring to mid-summer, the juvenile nymphs emerge and begin sucking sap from the plant. Shortly afterwards, the nymphs permanently affix themselves to the tree and form a crusty or waxy protective shell over their bodies. During the lifecycle of scale insects, their only movement is during their nymph period.
Scale damages trees by sucking sap from the trees vascular system, denying the tree vital nutrients. If uncontrolled, a major infestation can kill a tree in two to three seasons.
To control scale insects effectively and limit damage, Horticultural Oil Insect Spray should be sprayed on the tree in late winter and again before spring bud break. The Horticultural oil serves to suffocate the scale and eggs. In the spring, if the crawling nymphs are present, spray the trees with Bug Buster Pyrethrin Insect Spray to prevent the new nymphs from further infecting the tree.