黄杜鹃提取物对几种害虫的生物活性及其作用机理的初步研究

本文对黄杜鹃花提取物进行了生物活性研究。同时报道了黄杜鹃花提取物对粘虫、小菜蛾的拒食和胃毒活性试验以及对菜青虫的盆栽防治试验。并对黄杜鹃提取物较纯组份FC—22的作用机理进行了初步研究。结果发现,黄杜鹃氯仿、苯及二氯甲烷抽提物都有较高的活性。害虫取食黄杜鹃活性物质后会迅速出现兴奋、痉挛、呕吐等症状。FC—22是目前我们分离出活性最高的组份。150ppmFC—22对五龄粘虫幼虫的拒食率达93％。FC—22对三龄粘虫的LC_(50)为209ppm。对小菜蛾抗性及敏感两个品系的比较试验表明,抗杀灭菊酯的小菜蛾对黄杜鹃花二氯甲烷提取物没有表现出抗性。黄杜鹃提取物对菜青虫的盆栽防治效果较好,残效较长,在施药初期黄杜鹃提取物对菜白蝶有明显的产卵忌避作用,对孵化后的菜青虫一岭幼虫有较强的毒杀作用,但无杀卵作用。另外,对粘虫呼吸作用及多功能氧化酶测定结果表明,黄杜鹃提取物FC—22对粘虫幼虫的呼吸作用有一定影响,对粘虫的多功能氧化酶活性有诱导作用。

PRELIMINARY STUDIES ON THE BIOLOGICAL ACTIVITY OF EXTRACTS FROM RHODODENDRON MOLLE AGAINST INSECT PESTS AND THEIR MODE OF ACTION

This paper reports experiments with extracts from flowers of the yellow azelea (Rhododendron molle) on several agricultural insect pests. It was found that the crude extracts of R. molle possessed high antifeedant and stomach poison activities against several species of agricultural insects. Dichloromethane extracts (FCb) from the flowers of R. molle showed high toxicity against the third instar larvae of the diamond-back moth (Plutella xylostella). A strain of the moth highly resistant to fenvalerate showed no resistance to the fraction FCb. the LC50 of the resistant and sensitive diamond-back moth populations to FCb was 0.33% end 0.37% respectively. The insects showed symptoms of excitment, spasm and vomiting quickly after eating the extracts of R. molle, but they were killed slowly. Among the extractions of R. molle, the fraction FC-22 was found to be the most potent. The fifth instar larvae of the oriental army worm (Mythimna separata) showed more than 90% inhibition of feeding when treated with 150 ppm of FC-22. The respiration of the fifth instar larvae of M. separata was markedly depressed after eating a small amount of the extract FC-22. Increased multifunction oxida-se (MFO) activity was induced by the extract FC-22. The results of our experiments also showed that the extracts of R. molle had a strong oviposition deterrent effect on the females of pieris rapae under green-house conditions. Results of potted trials demonstrated that cabbages were protected from the damage of the larvae of P. rapae by spraying with 0.5% of extracts from flowers of R. molle. Since R. molle showed efficacy in the control of agriculral insects, it seems to be promising as a botanical insecticide for use in integrated pest management programs of vegetable insects in China.