Effectiveness of sterile boll weevils (Coleoptera: Curculionidae) against naturally occurring populations in commercially grown cotton

Boll weevils, Anthonomus grandis grandis Boheman, sterilized by feeding on an ecdysteroid followed by irradiation (10 krad in nitrogen) were released directly onto cotton plants by two new methods: a liquid method and a container method. Egg hatch on ca. 73 ha of commercially grown cotton was reduced from 98.1 plus or minus 0.78% in the untreated fields (26 ha) to 52.6 plus or minus 3.1% in fields in which sterile weevils were released (47 ha). Average ratio of sterile to native weevils was 6.4:1, and competitiveness of sterile weevils to native weevils was 11.4%. Effectiveness of the sterile weevils was attributed to two major factors: 1) release methods, and 2) preirradiation use of an ecdysteroid that does not appear to aggravate the effects of irradiation.