Screening For Inducement Factors Of Bursaphelenchus Xylophilus And Nematicides Against Bursaphelenchus Xylophilus

Pine wilt disease is a fatal epidemic disease for pine trees and it has continuously spread since it took place. However, there hasn't been any breakthrough and the most effective measure for now is focusing on prevention. So, the early diagnosis for pine wilt disease is of paramount importance. Therefore, this study aimed to screen Bursaphelenchus xylophilus-inducing substances in order to enhance the efficiency of early diagnosis tube for pine wilt disease, and to screen substance that can terminate PWN in infected trees and can deal with pinewood from Epidemic Regions.1. Screening for inducement factors of Bursaphelenchus xylophilusFour plants were selected for this study: Horsetail pine (Pinus massoniana),chinaberry (Melia azedaeach),mulberry (Morus alba) and Chinese fan palrr (Livistona altissima). Their leaves, twigs and fruits were ground, soaked or boiled with sterile water to extract the effective ingredients. The PWN-inducing experiments were conducted using sterile sands as medium and using Botrytis cinerea and sterile water as control, and the result showed that chinaberry twigs soaking extract and pine twigs soaked extract could effectively induce PWN. Chinaberry twigs soaking extract had the best inducing capacity (the choosing factor was 26.01%, 21.26% higher than Botrytis cinerea). The second best one was pine twigs soaked extract (the choosing factor was 19.48%, 8.89% higher than Botrytis cinerea). Chinaberry leaves soaked extract had almost the same inducing capacity as Botrytis cinerea and the other extracts had less capacity than Botrytis cinerea.Further test on pinewood confirmed that chinaberry twig soaked extract had the most effective inducing capacity, with the choosing factor 33.60%; Botrytis cinerea and pine twigs soaked extract were less, with the choosing factor as 19.41% and 8.60% respectively. The result showed that chinaberry leaves soaked extract worked well both in laboratory and in field. So, we can use it to develop chinaberry leaves soaked extract early diagnosis tubes. Applying this method can effectively detect pine wilt disease in the first stage, and save pine trees from skinning which could help to protect the scene of pine forests. 2. Screening for nematicides against Bursaphelenchus xylophilusSoak bioassay of 13 chemical medications was tested for B. xylophilus kill capacity in different conditions in order to screen effective PWN kill substances and to provide supportive evidence for PWN-chemical-prevention and cure measure. Acute toxicity experiments showed that among the 6 solid substances, NaOH, CuSO₄, ZnSO₄ presented effective capacity, which could kill PWN even in low concentration; their LC50 of 24h was 12.11 mg/L, 14.06 mg/L and 19.68mg/L, respectively. KI had poor effect, with LC50 of 24h 105.93 mg/L. Dipterex and NH4C1 had the poorest effect, with LC₅₀ of 24h 1778.28 mg/L and 3076.10 mg/L, respectively. The toxicity effect of 7 liquid substances were: formaldehyde > acetaldehyde > lactic acid > acetic acid> acetone > methanol > lsopropylalcohol.Toxicity experiments on PWN-incubating pinewood indicated that NaOH and CuSO₄ had the most effective toxic capacity, with LC₅₀ of 33.84 mg/L and 34.09mg/L, respectively. Further test on 50cm-long pinewood showed that by injecting medicine in holes on the wood for 30 d, 5% NaOH killed 89.50% PWN and 5% CuSO₄ killed 92.46% PWN.;...