Effect Of Bemisia Tabaci Type B On Tobacco Quality And Chemical Control

Bemisia tabaci (Gennadices) is an important invasive pest in our country recently, it widespreads in the main tobacco-growing areas in Shandong province. The occurrence of Bemisia tabaci in the tobacco-growing areas in Shandong , effect of different planting methods on the occurrence and effect of Bemisia tabaci on tobacco qualities were studied, the toxicity of several insecticides to different instars nymphs of Bemisia tabaci and the repellent actions to the adults were also studied. It can provide guidance to the scientific theoretical basis for prevention and treatment. The major results were as follows:1. Population dynamics of Bemisia tabaci adults in the main tobacco-growing areas in Shandong province was studied. The results showed that Bemisia tabaci adults began to occur in early June, as temperatures rised, the number in late July had risen sharply, in early August reached a peak, 3600 per 100 tobaccos, 3000 was still in early September. With leaf harvest, Bemisia tabaci transferred to other winter hosts.2. Effect of different planting methods on the occurrence of Bemisia tabaci was studied. In three kinds of planting methods, the sequence of Bemisia tabaci number was as follows: interplanting sweet tobacco> interplanting soybean tobacco> exclusively for tobacco.3. Effect of Bemisia tabaci damage on the external quality of tobacco was studied. Leaves damaged by Bemisia tabaci matured earlier than controls, mature time showed a certain relationship with the density, leaves with 5.0 adults per cm2 matured 8.8 days earlier, and leaves with 2.0 adults per cm2 matured 7.3 days earlier. As the amount of adults increased, mycophenolate polluted area of disease leaves had a larger proportion of the area. Small-density Bemisia tabaci damaged, the damage index wasâ…¢, and large-density damaged, the damage index wasâ…£.4. The main quality indexes of leaves damaged by Bemisia tabaci were studied. The results showed that the total alkaliods content of tobacco leaves damaged by Bemisia tabaci reduced; total nitrogen, protein, potassium, reducing sugar and total sugar content increased, they all had a certain relationship with the density.5. The changes of the volatile components from leaves damaged by Bemisia tabaci using of SPME and GC-MS were studied. The results showed that, the controls volatilized 58 components whose contents were more than 2.1%; while leaves damaged by large-density Bemisia tabaci had 69 volatitle components, and leaves damaged by small-density Bemisia tabaci had 59. Volatile components from leaves damaged by Bemisia tabaci with different density changed significantly.6. Toxicity of several insecticides to different instars nymphs of Bemisia tabaci and the repellent actions to the adults were detected in this paper. The results showed that avermectins, imidacloprid, cyhalothrin, thiamethoxam, nitenpyram and methomyl all had high toxicity to the adults of Bemisia tabaci, compared to buprofezin, the toxicity ratios were 3625.3, 873.4, 841.4, 312.8, 154.3 and 53.4, respectively. Pyriproxyfen had the highest toxicity to the eggs, the LC50 value was 0.0091 mg/L, compared to buprofezin ,the toxicity ratio was 91151.9. Avermectins, thiamethoxam, imidacloprid, nitenpyram, lufenuron and cyhalothrin all showed high toxicity to 1st instar nymph, and the toxicity to 1st instar nymph was higher than to 3rd instar. Three IGRs such as buprofezin, lufenuron and pyriproxyfen effected on the nymphs slowly. Thiamethoxam and imidacloprid had higher repellent actions to the adults, and the persistent repellent actions lasted 15 days. Lvying petroleum oil showed high toxicity to the eggs and high repellent action to the adults .it had practical value.