Scale Of Oak

Disease Information


Symptoms and damage

 Various kinds of scale are pests of oak. Scales are unusual insects in appearance. As adults, they are small and immobile, with no visible legs. They vary in appearance depending on age, sex and species. Scales feed on sap by piercing the leaf or stem with their mouthparts and sucking. As they feed on plant sap, some scale insects (soft scale) excrete a sugary substance called honeydew. The sooty mold fungus feeds on the honeydew, resulting in unsightly, dark fungal growth.


Scales are not easily controlled with chemical insecticides. The adults are protected by their waxy covering. For heavy infestations of scale insects, spray with horticultural oil in the spring and fall to kill adults, crawlers and eggs by smothering them. Be sure to thoroughly coat the trunk and all of the branches.
Crawlers are susceptible to conventional insecticides, however. Monitor the crawler emergence with sticky cards, double-faced tape wrapped around a branch, or by putting an infested shoot or leaf into a baggie and watching for crawler movement. Insecticides labeled for use by homeowners against scale crawlers on oaks include cyfluthrin, permethrin, bifenthrin, lambda cyhalothrin, malathion, and carbaryl. Apply one of these materials when crawlers appear and repeat in 10 days. As with all pesticides.


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