Development of gamma irradiation as a quarantine treatment of mites on cut flowers.

摘要

Cut flowers are an important export commodity of Malaysia in international trade. It constitutes RM 44 million for its foreign earnings and is often subjected to infestation by various pests such as mites, scale insects and thrips. Irradiating red spider mite, Tetranychus piercie, at a dose of 300 and 400 Gy produced sterile female adults from irradiated protonymphs and deutonymphs respectively. A lower dose of 200 Gy induced sterility in female adults developed from less immature stages of irradiated eggs and larvae. Deteriorating effects caused by irradiation treatment were reflected in immatures by their reduced emergence rate/mortality in subsequent developmental stages. A dose of 280 Gy prevented reproduction in female adults of Tetranychus piercie by inducing sterility while a much higher dose of 500 Gy is required to produce instant mortality. Large scale testing showed that deutonymphs require 350 Gy to produce sterile adults. Based on the results obtained gamma irradiation of dose range 350 Gy may be applied as a quarantine dose for sterilizing all stages of Tetranychus piercie as these stages could be available in the consignment. Tolerant dose of cut flowers is the highest dose that can be applied to the plant without any visible injuries in terms of quality and appearance. The tolerant dose for roses is 100 Gy, for carnation 200 Gy, for orchids 100-300 Gy depending on the variety tested. The cut chrysanthemum can tolerate 200-400 Gy depending on the variety tested. However, chrysanthemum in 4% sucrose solution can tolerate doses of 750 Gy. Based on the results obtained, the quarantine sterilizing dose for Tetranychus piercie is 350 Gy and it is only suitable for chrysanthemums..