Anatomical changes in the mature larvae of two Dacus spp. following irradiation

Fruit flies of the Tephritidae family are regarded as one of the most important global pests of quarantine importance. Ethylene dibromide was widely used to disinfect the potential host fruits and vegetables in international trade, but the ban imposed on the use of this chemical fumigant led to contemplation of irradiation as an alternative treatment method. Before suggesting irradiation as a suitable quarantine treatment, emphasis should be placed on standardizing a method for identifying the treated insects to ensure that a particular fruit assignment has been irradiated with the required dose. A description is given of a distinct reduction in area of the supraoesophageal ganglion (about 72-76%) along with the non-responsive proventriculus in third instar melon fly, Dacus cucurbitae Coquillett, and oriental fruit fly, D. dorsalis Hendel, larvae treated at several stages of larval development with various doses of gamma irradiation. It is suggested that this reduction in size of the ganglion be used as a direct method for determining if any fruit fly larvae found in a fruit or vegetable shipment at the port of entry have been irradiated. (author). 8 refs, 1 fig., 2 tabs