Experiments on the chemo sterilization of the lychee stink bug tessaratoma papillosa
Lin C S.; Chiu S F.
Acta Entomologica Sinica 26(4): 379-386
In Guangdong Province [China], there are 2 sensitive periods [for germ cell injury and inducing dominant lethals] of the male germ cells of the T. papillosa Drury to the reaction of the chemosterilant Thiotepa [tris (1-aziridinyl) phosphine sulfide]. These 2 periods are in the middle of July and the middle of Feb. of the following year, respectively. It is only during the period of the induction of lethals, that the treatment by chemosterilants gives good results. During mid Feb. when normal females mated with males dipped with 0.6% Thiotepa aqueous solution, 95% of the deposited eggs failed to hatch. In the same period when normal females mated with males fumigated with Bisazir [p, p-bis (1-aziridinyl)-N-methyl phosphinothioic amide] for 2.6 h and then dipped with 0.2% Thiotepa 93% were unhatched. These treatments seem to have no effect on the mating competitiveness and vitality of the males. Results of preliminary field experiments carried out in large nylon screen cages (2.2 .times. 2.2 .times. 3m) with a large lychee tree inside showed that when the bugs were released in the proportion of 80:10:10 (chemosterilized males: normal males: normal females), the percentage of unhatched eggs deposited by the females was 94.4% for Thiotepa dipping and 96.5% for Bisazir fumigation plus Thiotepa dipping treatment. The sterilization of eggs was favorable to the parasitization of the egg-parasite, Ooencyrtus sp. Chemosterilants appear to be a promising method for the control of this serious pest of lychee trees in south China. Observations on the sperms in the seminal vesicle of the male treated with 0.4% Thiotepa in Feb. with scanning electron microscope showed that the density of the sperms was decreased and irregularly arranged. Examinations under transmission electron microscope on the cross sections of the sperms and the testis of the males treated with 1.8% Thiotepa in Feb. showed that the axial filament was injured in some sperms.