Suppression of Boll Weevil (Coleoptera: Curculionidae) Infestations on South Texas Cotton by Augmentative Releases of the Parasite Catolaccus grandis (Hymenoptera: Pteromalidae)

Augmentative releases of Catolaccus grandis (Burks) were conducted in a series of south Texas cotton fields during 1992 (April 30-June 29) in an attempt to suppress infestations of boll weevil, Anthonomus grandis Boheman. Within each of three release sites, the average incidence of mortality occurring among susceptible host stages (94.4-96.4% and 86.1-96.6% apparent mortality among third-stage larvae and pupae, respectively) was substantially greater than that occurring among these same stages in controls devoid of parasites (2.2-9.6% and 1.8-7.9% apparent mortality, respectively). Such differential mortality produced two important effects: (1) a significant reduction in densities of adult boll weevils produced in release sites relative to controls (0.0-0.1 and 0.3-1.6 unemerged adults/m2, respectively), and (2) a concomitant reduction in the incidence of damaged bells during the postbloom period (0.2-0.4% and 48.3-91.7% in release and control sites, respectively). These results conclusively demonstrated the ability of C. grandis to suppress and maintain boll weevil infestations at subeconomic levels when augmented in sufficient quantities during the period in which the first and second host generations normally develop on cultivated cotton. The potential for augmentative biological control of boll weevil in the south Texas cotton environment is discussed.