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Abstract
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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.
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