a laboratory investigation on the effect of mbnpv and indoxacarb against the beet armyworm, spodoptera exigua (lep., noctuidae) larvae

beet armyworm, spodoptera exigua hübner, (lep., noctuidae), is one of the most important polyphagous pests of sugar beet in iran and many other countries. in most cases, this pest needs to be controlled for a few times in a crop season. baculoviruses are effective biological control agents which could be integrated to control program of this pest with other integrated pest management (ipm) elements. considering this target, we did some experiments using mbnpv and indoxacarb against the different larval stages of s. exigua. on the basis of preliminary tests, the applied doses were 185 pib/mm2 and 3.75 µg/mm2 leaf area for virus and indoxacarb, respectively. it was found that there were significant differences among different larval instars for susceptibility to virus such that susceptibility decreased as larval instar increased. there was no significant difference between two successive instar larvae for susceptibility to indoxacarb although, overally, susceptibility decreased as larval instar increased. according to the results, if treatment of virus is used on early instars of s. exigua, this may lead to substantial mortality of this pest.