مشخصات پژوهش

In this study fumigant toxicity of three different extracts of Ageratum houstonianum and Xanthium strumarium (Asteraceae family) on adults and first larval instar of potato tuber moth Phthorimaea operculella (Zeller, 1873) (Lep., Gelechiidae) was investigated. This insect is one of the important dangerous pests in field and storage condition on potatoes worldwide. For experiments, insects reared in controlled condition of 26±2ºC, 50±5% RH and a photoperiod of 16: 8 (L: D) h on potato tubes. For preparing the extracts of tested plants, the fresh leaves of plants collected, washed with distilled water, air dried in shadow condition and room temperature. The hexane, dichloromethane and acetone extracts prepared by maceration method [2]. The fumigant toxicity bioassays carried out in 10 and 100 ml vials (for 1st instar larvae and adults respectively). The 1st larval instars also adults were exposed to different concentration of given extracts by a piece of filter paper located on the tip of vials [1]. The results revealed that the extracts of studied plant extracts had minor fumigant toxicity effect on adults of PTM and the mortality was not significant in comparing with controls in exposure time of 24 hours, but with increasing the exposure time mortality increased in dose dependent manner. The first larval instars affected by plants extracts in dose dependent manner, although the fumigant toxicity of X. strumarium on adults was negligible but the LC50 values of hexane, dichloromethane and acetone extracts of A. houstonianum were 0.284, 0.546 and 0.236 g/l respectively and the slop of doseresponse lines obtained from probit analysis (SPSS v15) were 2.46±0.39, 1.76± 0.2 and 1.6±0.3 for hexane, dichloromethane and acetone extracts of A. houstonianum respectively. It suggests that, the acetone, hexane and dichloromethane extracts of this plant could be a potent candidate in non-chemical control of potato tuber moth, in storage condition.