Introduction Directory UMM :Data Elmu:jurnal:I:Insect Biochemistry and Molecular Biology:Vol30.Issue8-9.Sept2000:

Insect Biochemistry and Molecular Biology 30 2000 891–897 www.elsevier.comlocateibmb Biological activity of two juvenoids and two ecdysteroids against three stored product insects Moshe Kostyukovsky a, , Bin Chen b , Shulamith Atsmi a , Eli Shaaya a a Department of Stored Products, ARO, The Volcani Center, Bet Dagan 50250, Israel b Department of Plant Protection, Southwest Agricultural University, Chonqing 400716, China Received 31 October 1999; received in revised form 31 December 1999; accepted 25 January 2000 Abstract The insecticidal activity of juvenile hormone agonists methoprene and pyriproxyfen, and the ecdysone agonists RH-5849 and tebufenozide was evaluated against susceptible and actellic-resistant strains of Tribolium castaneum and susceptible strains of Rhyzo- pertha dominica and Sitophilus oryzae. Concentrations ranging from 0.1 to 20 ppm of the analogues were mixed in the food medium to which the tested insects were exposed. The results showed that all these compounds could affect the development of the tested species to differing extents but had no effect on the mortality of parental adults. The two JH analogues did not prolong the life span of R. dominica and S. oryzae, but very greatly extended that of T. castaneum. The extension led to the production of giant larvae and failure to pupate. Actellic-resistant strain of T. castaneum showed some cross-resistance to methoprene and pyriproxyfen, but not to RH-5849 and tebufenozide. Pyriproxyfen was the most effective compound among the four IGRs; a concentration of 0.1 ppm could completely inhibit the F 1 adult occurrence of both S- and R-strains of T. castaneum and its LC 90 s for controlling R. dominica and S. oryzae were 0.1 and 1.2 ppm, respectively. Methoprene was highly effective against R. dominica, but less active on S. oryzae. RH-5849 could achieve almost complete control of F 1 adults of T. castaneum and R. dominica at 10 ppm, but was less potent on S. oryzae. Tebufenozide appeared to be much less active on these three species compared with the other three compounds. The percentage reductions of F 1 adults for S- and R-strains of T. castaneum at a concentration of 20 ppm were 80 and 99, respectively.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Juvenile hormone; Ecdysone agonist; Methoprene; Pyriproxyfen; RH-5849; Tebufenozide; Tribolium castaneum; Rhyzopertha dominica; Sitophilus oryzae

1. Introduction

The use of fumigants and conventional organic insec- ticides to control insect pests of stored products has given rise to problems of residual toxicity and develop- ment of resistant strains of insects. These problems have enhanced the need to develop more effective and rela- tively safer insecticides Smet et al., 1990. Insect growth regulators IGRs can degrade rapidly in the environment Staal, 1975; Zurfleuh, 1976 and generally have low mammalian toxicity to non-target species Staal, 1975; Oberlander et al. 1978, 1997. They are effective against some strains which are resistant to con- Corresponding author. Tel.: + 972-3-968-35-84; fax: + 972-3-960- 44-28. E-mail address: inspectagri.gov.il M. Kostyukovsky. 0965-174800 - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 5 - 1 7 4 8 0 0 0 0 0 6 3 - 1 ventional insecticides Amos et al., 1974; Silhacek et al., 1976. Some IGRs have a very high biological activity Slama et al., 1971, 1974 and could potentially be inte- grated in other insect pest management techniques IPM such as biological control Wright and Spades, 1972. Many studies have demonstrated the effects of a variety of IGRs on various stored product insects Thomas and Bhatnagar-Thomas, 1968; Silhacek and Oberlander, 1975; Loschiavo, 1976; Nickle, 1979. All of these characteristics make them potentially successful alterna- tives to standard pesticides for insect pest control. IGRs include compounds that may affect molting and metamorphosis by mimicking juvenile hormone JH, juvenile hormone agonists or antagonizing JH activity ecdysteroid agonists or by interfering with cuticle for- mation chitin synthesis inhibitors Smet et al., 1990; Oberlander et al., 1997. Worldwide, Tribolium castaneum Herbst, Rhyzoper- 892 M. Kostyukovsky et al. Insect Biochemistry and Molecular Biology 30 2000 891–897 tha dominica Fabricius and Sitophilus oryzae Linnaeus are all economically important pests of stored products, which feed on a wide range of commodities Arbogast, 1991. Repeated pesticide treatments have led to the increasing incidence of resistance and consequent serious control problems of these species in certain cases Subramanyam and Hagstrum, 1996. The objective of this study was to compare the efficacy of the juvenile hormone agonist methoprene which is in use as control agent against insect pests of stored products, to the juv- enile hormone agonist pyriproxyfen, and two ecdysteroid agonists, RH-5849 and tebufenozide.

2. Materials and methods