Irradiation as a quarantine treatment for the solenopsis mealybug, Phenacoccus solenopsis

Phenacoccus solenopsis is an aggressively invasive species that targets agricultural and ornamental plants, thereby threatening the world cotton industry and other crops. P. solenopsis has been listed as a quarantine insect in Europe and China. The utilization of phytosanitary irradiation as a potential treatment for disinfesting agricultural commodities in trade has expanded rapidly in recent years. A reasonable dose of radiation to eliminate P. solenopsis needs to be determined, taking into account the side effects of radiation on agricultural products and the species-specific tolerance of the insect to radiation. We applied radiation ranging from 50 to 200Gy to P. solenopsis to determine the optimal dose. Both the radiation dose and the developmental stage of the insect were independent variables. Higher doses of radiation or lesser mature insect stages provided more effective treatment. In nymphs, a radiation dose of 100Gy caused extinction of the irradiated population by disrupting ovary development, while 150Gy caused 100% mortality. In adults, all tested doses of irradiation did not affect longevity, but we were able to prevent reproduction with high (150 and 200Gy) doses. In P. solenopsis, a 100Gy dose of radiation could eliminate the irradiated population in two generations. The mortality curve showed a steep slope beyond 150Gy; thus, if killing all of the insects in a shorter amount of time is necessary, 200Gy may be a reasonable dose for the quarantine treatment of the solenopsis mealybug. •Both ‘radiation dose’ and ‘irradiated insect stage’ are important factors.•100-Gy irradiation could achieve population extinction in two generations.•200Gy should be a reasonable dose in the quarantine treatment.