אסיף מאגר המחקר החקלאי

Comparative toxicity of two ecdysteroid agonists, RH-2485 and RH-5992, on susceptible and pyrethroid-resistant strains of the Egyptian cotton leafworm, Spodoptera littoralis

Year:

1995

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Volume :

23

Co-Authors:

Ishaaya, I.
Yablonski, S.
Horowitz, A.R., Dept. of Entomology, ARO, Volcani Center, Bet Dagan, 50250, Israel

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Abstract:

The comparative toxicity of two non-steroidal ecdysteroid agonists, RH-2485 and RH-5992 (tebufenozide), on development stages, fecundity and egg viability of a susceptible laboratory strain and a pyrethroid-resistant field strain of Spodoptera littoralis (Boisduval) was evaluated. Taking the LC50s as the criterion, RH-2485 was 3–7-fold more potent than RH-5992 against the susceptible and 7–14-fold more against the field strain. The LC50 of RH-2485 in the 1st and 6th instars of the susceptible strain was 0.32 and 0.57 mg a.i./l, respectively. The field strain showed a mild cross-resistance of about threefold to both compounds in 1st instars and to a lesser extent in 6th instars. A considerable increase in fecundity (~3-fold) and no effect on egg viability was observed when 6th instars were fed on cotton leaves treated with 0.25 mg a.i./l RH-2485 (~LC40). Our results indicate that both compounds are potentially potent insecticides for controlling S. littoralis larvae, being 10-60-fold more potent than a previous ecdysteroid agonist, RH-5849. © 1995, Springer Science + Business Media B.V.. All rights reserved.

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