Competitiveness of Sterile Boll Weevils (Coleoptera: Curculionidae) Relative to a Native Population in Small Field Plots

Sterile Anthonomus grandis grandis Boheman were 50.4% as competitive as native boll weevils in three 0.4-ha field plots. These weevils, released semiweekly for 2½ weeks, had been fed for 3 days on slabs of diet that contained 0.2% of an ecdysteroid, 3β, 5β, 14α-trihydroxy-5β-cholest-7-en-6-one, and 0.03% each of two antibiotics, kanamycin and chloramphenicol, before irradiation (10 krad in nitrogen). The high degree of competitiveness was attributed to three factors: addition of effective antibiotics to the adult diet, use of the ecdysteroid as a chemosterilant for females, and shortening of the release interval to 3–4 days.