Toxicities Of Different Nematicides To Bursaphelenchus Xylophilus And Their Safety Evaluations

The thesis studied the selection of nematicides controlling the Pine Wilt Disease in laboratory, trank injection of nematicides and safety evaluation of nematicides to Pinus massoniana. The main results were summarized as follows:(1)The toxicity of 19 single nematicides on Bursaphelenchus xylophilus were tested by means of immersion in laboratory. The result showed that No.17 had the strongest nematicidal activity against the B.xylophilus. And No.33, No 25, No.1 and No.12 had weaker nematicidal activity than N0.17. The enhanced toxicity on B.xylophilus was also observed in determination of combined application of nematicides, and the most significant mixtures were No.37+No.25 and No.17+N0.1+No.25.(2)Three models had been established by fitting total volume and diameter at breast height (DBH) of P.massoniana. The result showed that second-order quadratic function was more suitable than power, linear functions, and their correlative coefficients were 0.9509, 0.9458 and 0.9209, respectively.(3)The optimum model of P.massoniana provided a theoretical basis for calculation of individual injection dosage by trunk injection. Furthermore, from the aspect of the empirical dosages by trunk injection in the world, the actual injection dosage was got finally. In practice, nematicides could be injected at the dosage of 10ml per tree to P.massoniana under 10cm of DBH, and 40ml, 70ml, 110ml, 190ml,310ml to 10~15cm, 15~20cm,20~25cm, 25~30cm and 30~40cm of DBH.(4)Field experiments showed that the absorption of No.17,No.25 and No.17+No.1+No.39 were quicker than other nematicides. Toxicity of water extracts from branches of P.massoniana treated against B.xylophilus was measured in laboratory to evaluate the nematicidal activities after trunk injection. Results indicated that the nematicides selected had obvious control effects, comparing with the control.(5)After trunk injection, four physiological and biochemical indexes in needles of P.massoniana changed in varying degrees. All of the six nematicides tested could cause the decreasing of the amount of soluble sugar. While the content of dissociative praline increased in short time after treatments, and then reached to the control level along with the prolonging of time. In addition, the effect on chlorophyll and MDA contents varied with the species of nematicides.