SAN JOSE SCALE

(Aspidiotus perniciosus), one of the most destructive scale insects (order Homoptera), first discovered in North America at San Jose, Calif., in 1880 but probably a native of China. The yellow-coloured females are covered with a gray circular scale (a protective waxy shell which they secrete) about 1.5 mm (0.06 inch) in diameter, elevated in the centre and surrounded by a yellow ring. After mating, the female produces living young. There may be two to six generations per year. Sometimes San Jose scales become so numerous that they overlap and completely cover tree branches; in time they may kill a tree. A lime-sulfur spray was once used as a control measure, but an oil spray is now far more effective.