Walnut scale

The walnut scale is often found in daisy-shaped groups that develop when male crawlers settle under the margin of the circular female cover and begin forming their elongated covers. If the circular scale covering is lifted off the female, the body underneath is yellowish and has indented margins; these two characteristics help distinguish walnut scale from other armored scales on walnuts.
The walnut scale has two generations a year in the Central Valley. It overwinters as second instar females and males. In spring, both sexes resume development and mature at the same time. Adult males emerge from the scale covering as tiny winged insects to mate with the mature females, who remain under the scale covering. After mating, females lay eggs in mid-May; eggs hatch in 2 to 3 days. Female crawlers move around the branches for a short time before they settle down, begin feeding, and secrete the scale cover. Male crawlers move to the margins of a female cover and settle. Initially the scale cover is white (white cap stage), but it changes to gray or brown after about a week. The first generation completes development by mid-July; females lay eggs in mid-August. These eggs hatch and the crawlers settle and molt once before winter.