Abstract
Seasonal phenology of the walnut scale, Quadraspidiotus juglansregia (Com stock), was studied for 5 yr on Acre rubrum L., and emergence of adult males and crawlers was related to physiological time (i.e., degree-days [DD]). The scale is Nicoline in Kentucky, and both sexes overwinter as second-instar nymphs. This pattern differs sharply from previously published life history data for Q. juglansregiae on other hosts and suggests that the walnut scale, as it is currently understood, may actually represent a species complex. Date of first hatch of crawlers ranged from 30 May to 17 June and corresponded to a mean accumulation of 785 DD (base 4.44°C) from 1 January. Four primary parasites and two hyper parasites were found associated with Q. juglansregiae on red maple. The encyrtid Coccidencyrtus ensifer Howard, the most abundant primary parasite, emerged from first and second generation adult female scale insects. Application of insecticidal sprays in June or August for control of walnut scale crawlers will unfortunately alsocoincide with the period of peak activity of the scale’s primary parasites.
Published Version
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