species-includingPulvinaria acericola, Pulvinariainnumerabilis and Melanaspis tenebricosa are pests of maples. Scales are
unusual insects in appearance. They are small and immobile, with no visible
legs. Scales vary in appearance depending on age, sex and species. Some are
flat and appear like scales stuck to a plant, while others appear like white
Symptoms and damage
They feed on sap by piercing the leaf, stem or
branch with their mouthparts and sucking. Their feeding can weaken or kill
branches. Heavily infested trees are stunted with small flowers and leaves.
Leaves may yellow and drop early.
A combination of various natural
enemies, including ladybird beetles (ladybugs) and parasitic wasps, usually
keeps scales under control. In small trees with light infestations, scale can
be scraped off or infested branches can be removed and destroyed. In a large
tree, controlling scale chemically is not always practical. The size of the
tree, the need for specialized equipment and the cost may prohibit this
approach. Adult scales are relatively protected from insecticides by their waxy
covering. Their immature forms, called crawlers, are susceptible, however. If
it is determined that chemical control is necessary, the recommended chemicals
include the following: cyfluthrin, lambda cyhalothrin, bifenthrin, permethrin
or carbaryl. Apply materials when crawlers appear and repeat in 10 days. Soft
scales can be controlled by soil drenches with dinotefuran or imidacloprid.
Drench applications are best made in the spring. Dinotefuran may move into
trees more quickly than imidacloprid for faster control.