HELIOTHIS-VIRESCENS (LEPIDOPTERA, NOCTUIDAE) - INFLUENCE OF STERILE BACKCROSS RELEASES ON SUPPRESSION

A pilot test to suppress a wild tobacco budworm, Heliothis virescens ( F.), population by rearing and releasing insects with a sterile male t rait was conducted during 1991-94. Backcross moths with the sterile tr ait were released in a 16.7-km square area in Washington and Sunflower Counties, Mississippi, in 1992 and in Bolivar County in 1993. Pheromo ne traps were used to monitor insect populations in both areas during both years and the non-release area served as the control. Moth releas es were directed at the overwintered tobacco budworm emergence and wer e placed in the field 2 April to 15 May in 1992 and 12 April to 25 May in 1993. Approximately 69,000 moths per day were released in 1992 and 70,000 per day in 1993. A 3.0:1.0 released:wild ratio was achieved in 1992. This ratio dropped to 1.3:1.0 and 1.0:2.3 during June and July, respectively, due to moth movement into and out of the release area. Continued monitoring of this area in 1993 showed a 1.0:2.2 backcross:w ild ratio (29.9% (1)Department of Entomology, Mississippi State Univer sity, Mississippi State, MS 39762. sterility) carried over the winter. This ratio dropped to 1.0:5.2 backcross:wild in June, increased to 1. 0:4.7 and 1.0:3.4 during July and August, respectively. A 2.6:1.0 rele ased:wild ratio was achieved for the Bolivar County release in 1993. T his ratio declined to 1.0:1.6 in June, 1.0:3.6 in July and 1.0:4.0 in August. Continued monitoring in 1994 showed that male sterility in the overwintered populations across both release areas was 12.1%.