Irradiation as a quarantine treatment against Thrips palmi
Studies have been carried out in Japan on the use of irradiation against Thrips palmi (EPPO A1 quarantine pest) and T. tabaci, as alternative treatments are needed to replace methyl bromide fumigation. Eggs, second instar larvae and adults of T. palmi and T. tabaci were exposed to irradiation at doses of 0, 100, 200 and 400 Gy. For treated eggs of both species, it was found that younger eggs were more susceptible to the treatment. Some survivors could hatch and give larvae but could not reach pupal stage. For T. palmi, at a dose of 400 Gy, one larva was obtained (out of 386 treated eggs) but could not give a pupa. Concerning the treatment of second instar larvae, results showed that adult emergence of T. tabaci was inhibited at 200 Gy, while 1 male and 1 female of T. palmi could survive at 400 Gy (out of 126 treated larvae). But none of these 2 adults was able to produce descendants. When adults were treated, it was found that both species were sterilized at 400 Gy, but descendants were obtained at doses of 200 Gy and lower. The adult stage is the most tolerant to irradiation. The authors concluded that all stages of T. palmi and T. tabaci are sterilized or killed at 400 Gy. As previous studies have shown that no severe injuries were seen on many cut flowers irradiated at 400 Gy, it is felt that irradiation could be an effective quarantine treatment against T. palmi on cut flowers.
Sources
Dohino, T.; Tanabe, K.; Masaki, S.; Hayashi, T. (1996) Effects of electron beam irradiation on Thrips palmi Karny and Thrips tabaci Lindeman (Thysanoptera: Thripidae).
Research Bulletin of the Plant Protection Service Japan, no. 32, 23-29.