Field releases of two genetic sexing strains of the Mediterranean fruit fly (Ceratitis capitata Wied.) in two isolated eases of Tozeur governorate, Tunisia

The recent development of medfly genetic sexing strains (GSS) enables only male adults to be produced and released for area-wide control using the ste rile insect technique (SIT). Before these strains can be incorporated into large operational field programmes, information is required on all aspects of held performance. In a pilot project in -Tunisia, medfly pupae from GSS SEIB-40 [based on a pupal colour mutation (wp) and VIENNA-43/44 [based on a temperature sensitive lethal mutation (tsl) were shipped from the FAO/IAEA Agriculture and Biotechnology laboratory (Seibersdorf, Austria) and the em erged sterile males released weekly from the ground in eases of the Tozeur Governorate from mid-February until October 1994. During that period, flies emerging from an average of 5000 pupae per hactare were released weekly th roughout 105 hectares. Transportation problems were encountered which resul ted in damage to the pupae. Nevertheless, the monitoring of the wild popula tion through a trapping network using Jackson and McPhail traps showed that both strains performed equally well inducing a three- to five-fold decreas e of the wild population compared with the control oasis (10 wild flies per Jackson trap per day in October in Ain-El-Karma, five in Tamerza and 30 in Bir Kastilia control oasis). Considering the economical and technical bene fits inherent in the use of these new strains in the field and as a result of their good field performance, similar strains have been introduced into mass-rearing facilities in Guatemala (1994), Argentina (1995) and Madeira ( 1996).