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Saturday, January 10, 2009

Wax Scale Solitaire

I find these wax scales, Ceroplastes sp, all alone on the stems of woody perennials from time to time. The female adult scale shown here will overwinter and produce lots of brick red eggs in the cavity under her waxy shield. Scale insects are very destructive to plants when the infestation is heavy, as demonstrated in this photo at UC IPM. But I have not experienced bad infestations which indicates there is a healthy population of scale predators at work in the garden. When scale become a problem, try hand picking the adult females in winter, dormant oil sprays in winter to suffocate them, or in spring or summer when the larvae begin crawling. It's tricky to determine or notice exactly when the crawlers are present, but that is the correct time to spray oil. The use of broad spectrum insecticides may kill some scale but will also reduce the population of predators which are ultimately the very best control for scale and so this practice is not recommended.

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