Indirect Effects of Citrus Cultivars on Life History Parameters of a Parasitic Wasp

We determined sex ratio, initial egg complement, and size of adult Aphytis melinus, an ectoparasitoid of California red scale, Aonidiella aurantii. Host scales were reared on leaves of four citrus cultivars previously shown to differ in suitability for scale growth and survival. Wasps from scales reared on leaves of lemon (Citrus limon) produced nearly twice the proportion of female progeny as did wasps from scales reared on leaves of grapefruit (Citrus paradisi), orange (Citrus sinensis), or mandarin (Citrus unshiu). Moreover, female wasps from lemon—reared scales had highest initial egg complement, followed by wasps reared from grapefruit, mandarin, and orange. The quality of scales for the production of fecund, female wasp progeny also varied seasonally over all cultivars pooled. Scales reached largest size when reared in the cooler autumn temperatures and were more than twice as suitable for the production of fecund, female A. melinus as scales reared in early summer or midsummer. Results suggest that the mechanisms allowing persistence of the interaction between California red scale and A. melinus may vary among different citrus cultivars.