Toxicity Effects Of Commonly Used Fungicides In Greenhouse Melon Crops On Apis Cerana Cerana

Apis cerana cerana is endemic to Chinese honey bee as one of main pollination insects for traditional agriculture in China. It is important to promote plant genetic diversity and maintain ecological balance based on ecological and economic significance.In recent years, the number of bees significantly reduced. In addition, the interaction of parasites, viruses, pesticides and habitat loss may also affect the survival of bees. It had aroused widespread concern that the number of bee colonies is decreasing sharply even causing crop pollination crisis. In this thesis, the virulence and sublethal effect of ten fungicides against A. cerana cerana were carried out. The main contents and research results were as follows:1. The acute oral and contact toxicities of ten fungicides on A. cerana cerana were conducted by food intake method and drop method in laboratory, meanwhile we assessed the hazard and synergistic effect of these fungicides. The results of virulence evaluation indicated that both the acute contact toxicity (48h) of 12.5% myclobutanil EC (4.697?g a.i./bee for LD50), 25% propiconazole EC (7.261?g a.i. /bee) and 15% prochloraz ME(3.228?g a.i. /bee) and the oral toxicity of myclobutanil (2.154?g a.i. /bee for LD50) and propiconazole (5.176?g a.i. /bee) on bees were medium toxic, and prochloraz (1.817?g a.i./bee) was high toxic. The risk assessment results showed that three fungicides were medium risk for A. cerana cerana. The results of virulence evaluation indicated that the acute toxicity of seven fungicides, namely 80% mancozeb WP, 50% boscalid WG,50%procymidone WP, 50% dimethomorph WP, 100 g/L cyazofamid SC. 20% bismerthiazol WP and 2% kasumin AS on honey bees were low toxic.2. Using the self-made bee tower, study of myclobutanil, propiconazol and prochloraz formulation fungicides affect the flight force on A. cerana cerana by observation and recording. The worker bees were treated by myclobutanil, propiconazole and prochloraz of sublethal doses (LD5). Two flight bioassays were determined when bees were exposed to the fungicide after 48h. The first bioassay explored the vertical flight of honey bees towards the light source, and the 2nd flight bioassay explored the free-fall flight of the workers. The results showed that myclobutanil, propiconazol and prochloraz of LD5 did not significantly affect the flight performance of the whole worker bees in two flight bioassays. However, the individual worker bee significantly affected by these three fungicides, and there were significant differences (P<0.05) in the number of bees at the light source (120cm) and the bottom of the tower floor (0cm), respectively.3. Effects of sublethal doses of myclobutanil, propiconazole and prochloraz on the respiration rate of A. cerana cerana was determined by using low range respiration package. The respiration of worker bees contacted by myclobutanil of 1.790?g a.i. /bee or fed with 1.085?g a.i. /bee decreased with time (3 h. 24 h and 48 h). At 24h and 48h, the respiration rate of bees was significantly different (P<0.05) in two contact ways. After the worker bees were contacted by propiconazol of 3.937?g a.i. /bee or fed with 1.118?g a.i./bee, the respiration rate of bees was much lower than the control, and regarding the contact method the respiration rate increased at first and decreased subsequently. When the worker bees contacted prochloraz of 1.485?g a.i. /bee or fed 0.756?g a.i. /bee, the respiration rate of bees decreasing with time was significantly different (P<0.05) from prochloraz treatments. The results of respirometry bioassays showed that three kinds of fungicides had a certain impact on the respiration rate of A. cerana cerana.4. The activity effect of sublethal dose of myclobutanil on P450s and GSTs from A.cerana cerana was examined by enzyme inhibition test. The results showed that the high activity of GSTs was obviously induced when A. cerana cerana nurse bees contacted LD5 of myclobutanil TC at 48h and activity of P450s was low, but the activity of GSTs and P450s of foragers were not significantly different. Nurse bees and forager bees contacted different sublethal doses of myclobutanil,LD5 of formulation-grade myclobutanil significantly enhanced P450s activity from nurse bees while there was no apparent effect on GSTs. The other hand, there was no apparent effect on GSTs and P450s from forager bees treated with different doses of myclobutanil.