苦楝油防治桔全爪螨的研究

STUDIES ON THE CONTROL OF THE CITRUS RED MITE PANONYCHUS CITRI (McG.) WITH CHINABERRY SEED OIL

本文认为苦楝(Melia azedarach L.)油对桔全爪螨Panonychus Citri(McG.)的毒杀作用,可能是因油剂堵塞螨的气门造成窒息而死亡。用电镜扫描的方法比较了桔全爪螨和捕食螨的气门结构,指出气门结构的差异是产生选择毒性的主要原因。本文提出了乳化苦楝油的经济、简易、有效的配方和方法。室内测定,苦楝油对桔全爪螨LC_(50)为0.27％;大田防治试验的效果达93.7％,是一种优良的高效杀螨剂。利用植物油防治柑桔叶螨具有广阔的前途。

Results of bioassays showed that the chinaberry (Melia azedarach L.)seed oil was very effective as an acaricide for the control of the citrus red mite and was safe to the predatory mite Amblyseius newsami(Evans),an important predator,the LC50 for the mite and the predator being 0.27% and 1.63%,respectively.The mode of action of the oil against the citrus red mite was studied.Results of tests showed that the lipid,which consiste of glycorol and fatty acids,was the active ingredient which killed the mite.Based on the responses to treatments on various parts of the tody cf the mite with the oil emulsion,it was suggested that the blocking of the stigma caused by the oil film spreading on the mite body was the cause of death.Based on observation with the scanning electronmicroscope,difference in the structure of the stigma of P.citri and A.newsami was found.The stigma of the former is only an crevice on the gnathobase,without visible peritreme,and that of the latter is located between leg Ⅱ and leg Ⅲ in the flank of the podosoma,having wide peritreme in contact with the stigma and extending ahead to the forward position of the propociosoma.These differences in structure of stigma might account for the selective toxicity of the seed oil.Results of field experiments showed that a mortality of 93.6-96% was obtained by spraying with 0.5% seed oil emulsion,which was equal in effectiveness to that of 20% Amitraz at a concentration of 1,1000 against the red mite.At this concentration,on phytotoxic effect on citrus foliage during the growing period was observed.