RADIATION DOSES TO SAFELY RELEASE THE PARASITOID DIACHASMIMORPHA LONGICAUDATA REARED ON ANASTREPHA FRATERCULUS LARVAE .

BACHMANN, GUILLERMO E.; CARABAJAL PALADINO, LEONELA Z.; CONTE, CLAUDIA; DEVESCOVI, FRANCISCO; MILLA, FABIÁN H.; CLADERA, JORGE L.; SEGURA, DIEGO F. 1; VISCARRET, MARIANA M.

Congreso; VIII International Symposium on Fruit flies of Economic Importance; 2010

Background: Anastrepha fraterculus is a fruit fly of economic importance in Argentina and other countries in South America. Biological control programs based on the release of the braconid Diachasmimorpha longicaudata have been successful to control other flies of the genus Anastrepha. In order to release this parasitoid it is necessary to establish the radiation dose that, both, avoid fruit fly emergence from non parasitized pupae and, do not affect parasitoid performance. Methods: A. fraterculus larvae were irradiated with X-ray, at doses equivalent to: 60, 80 and 100 Gy (6250.2, 8333.6 and 10417.0 roentgens, respectively). Immediately after irradiation, larvae were offered to D. longicaudata mated females. A control group of irradiated larvae were not exposed to parasitoids. Number of emerged parasitoids, flies and non emerged pupae were registered. Emerged flies (if any) were crossed with non-irradiated flies and egg production and egg hatch were registered. For those parasitoids that emerged from irradiated larvae fecundity was determined. Fecundity was assessed by offering host larvae every other day, during 2 weeks. Results: Larvae irradiated at 60 Gy showed high level of emergence and were as fertile as control (non-irradiated larvae). At 80 Gy, only 1.4% of the pupae emerged, males having a significantly reduction in fertility. No flies emerged from larvae irradiated at 100 Gy. Parasitism rate on larvae irradiated at 80 or 100 Gy did not differ from that found in control (non-irradiated) larvae, nor did their offspring’s sex ratio. F1 fertility was also not affected by the radiation dose. Conclusions: These results suggest that irradiation with X-rays at a dose equivalent to 100 Gy applied to third instar larvae of A. fraterculus can significantly reduce the risk of release of adult fruit flies on the field without affecting the development and subsequent performance of D. longicaudata. This dose could be reduced to 80 Gy, as emergence will also be close to zero and emerged flies will be to a large extent sterile.