Action of a novel nonsteroidal ecdysteroid mimic, tebufenozide (RH‐5992), on insects of different orders

摘要

AbstractThe nonsteroidal ecdysteroid agonist tebufenozide (RH‐5992) was tested on larval stages of a number of lepidopteran species by topical application and by feeding on treated leaves. LC50, values in the range 0.03–0.10 mg litre−1were obtained for third to sixth instars ofSpodoptera exempta(Walker) when insects were fed on leaves dipped in aqueous emulsions of the compound, while first to fifth instars ofSpodoptera exigua(Hübner) were less susceptible (LC50values in the range 2.5–10.5 mg litre−1). When insects were topically treated, susceptibility of last‐instar larvae of Lepidoptera tested decreased in the orderSpodoptera exempta, Mamestra brassicaeL.,Spodoptera littoralis(Boisd.)S. exiguaandGalleria mellonellaL. Tebufenozide induced a premature and lethal larval moult in larval Lepidoptera within 24 h of treatment. Most larvae died in their old larval cuticle. Other aberrations included inhibition of weight gain and feeding, extrusion of the hindgut, loss of hemolymph and an abnormal and lethal pupation. In contrast, tebufenozide at similar doses/concentrations had no activity on larval instars ofLeptinotarsa decemlineata(Say) andDiabrotica virgifera virgifera(LeConte), nymphs ofPodisus sagitta(F.) and larvae ofLocusta migratoria migratorioides(R.F.). It had a chemosterilizing activity inS. exigua, resulting in a total inhibition of oviposition within two days of continuous treatment at doses of ⩾ 10 mg litre−1.On the other hand, all deposited eggs were viable. Similar effects on reproduction occurred inL. decemlineata, but at highe