Abstract
Seasonal phenology of the obscure scale, Melanaspis obscura (Comstock), was monitored for 4 yr on Quercus palustris M. in Lexington, Ky., and emergence of adult males and crawlers was related to physiological time (i.e., degree-days [DD]). This scale is univoltine in Kentucky and both sexes overwinter as second instars. Date of first hatch of crawlers during 1984-1986 ranged from 22 June to 6 July, corresponding to a mean accumulation of 1,521 DDC (2,737 DDF) calculated from a base of 4.44°C (400°F). This value accurately predicted crawler hatch dates in West Lafayette, Ind., and College Park, Md., in 1986, and in Lexington in 1987. Six species of primary parasites and one hyperparasite species were reared from scale-infested twig samples. Parasite flight periods were determined from sticky trap collections within tree crowns. Application of insecticidal sprays during July for control of obscure scale crawlers would unfortunately coincide with peak activity of the scale’s primary parasites.
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