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Abstract
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Integration use of different pest control tools is an important part of integrated pest
management programs in which biological control constitute an essential component of IPM
programs. Enhanced efficacy of biocontrol agents in the combination use of other components
has been recently shown. Increasing the efficiency of control agents’ especially microbial agents
because of many advantages in comparing with conventional pesticides is so important. One of
the useful techniques is combined use of two or more agents. This method in addition with
increasing the toxicity has beneficial effects on preventing the pest resistance development. For
evaluating such possibility in Potato tuber moth (PTM), Phthorimaea operculella, IPM, as one of
the important pests of potatoes, virulence of Bacillus thuringiensis Var. kurstaki was evaluated in
the presence of methanolic extract of Falcaria vulgaris against first instar larvae of P.
operculella. Insects were reared on potato tubers in controlled condition (26±2ºC, 50±5% RH
and a photoperiod of 16 hrs light). Potato foliage was washed with distilled water, and then dried
in room temperature. Extraction carried out using maceration method [1]. Three expected
sublethal dose of Bt and plant extracts including LC10, LC30 and LC50 determined and then
virulence on larva was again evaluated in different treatments as an observed mortality (MBF
mortality of PTM under BT and methanolic extract combination). Described method by Finney
(1964) [2] was involved for data analysis in which calculated chi-square according to: x2= (MBF -
ME)2/ME is compared to the X2 table value for df=1. Interaction was considered synergistic or
antagonistic when the calculated X2 value exceeded the table value. Results clearly showed that
interaction between Bt and methanolic extract across all studied exposure time synergistically
affected virulence against PTM regardless of mode of combination, highest and lowest
synergistic effects were recorded at LC50 BT &
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