Horticultural spray oils kill all stages of scales that are present at the time of application, and often give good control. Refer to the product label for guidelines on plant sensitivity and any temperature restrictions. Oil products labeled as summer, superior or Volck oil are of the highest grade and may be used on tolerant plants during either the growing season or the dormant season, but at different spray concentrations. An alternative to oil sprays are contact insecticides applied during the growing season when the crawler stages of the scales are present. The presence of crawlers can sometimes be determined by sharply tapping an infested twig or a white paper.
Crawlers are often orange, brown or purple and appear as moving specks of dust.
Because of their waxy protective covering, other stages of scales are not readily controlled by contact insecticides. Contact insecticide sprays will not reach crawlers that have settled under old scales. Although resistance to insecticides may occur in some cases, failure of contact sprays is more often the result of not timing the applications to coincide with crawler activity. Even when sprays are timed for optimum effect, complete control may not be achieved by single applications if crawler activity is spread over an extended period of time, or if populations are heavy and crawlers are under old scale shells. Thorough spray coverage is essential for good control.