Persistence and residual activity of an organophosphate, pirimiphos-methyl, and three IGRs, hexaflumuron, teflubenzuron and pyriproxyfen, against the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae)

Authors: Abo-Elghar G.E.¹; El-Sheikh A.E.¹; El-Sayed F.M.²; El-Maghraby H.M.³; El-Zun H.M.²

Source: Pest Management Science, Volume 60, Number 1, January 2004 , pp. 95-102(8)

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Abstract:

Three insect growth regulators (IGR), the chitin synthesis inhibitors (CSI) teflubenzuron and hexaflumuron and the juvenile hormone mimic (JHM) pyriproxyfen, as well as the organophosphate (OP) pirimiphos-methyl, were evaluated for their activity against the cowpea weevil, Callosobruchus maculatus (F), in cowpea seeds stored for up to 8 months post-treatment. The initial activity data showed that, based on LC₅₀ level, teflubenzuron had strong ovicidal activity (LC₅₀ = 0.056 mg kg^-1) followed by pirimiphos-methyl (1.82 mg kg^-1) and pyriproxyfen (91.9 mg kg^-1). The residual activity data showed that none of the IGRs tested had strong activity when applied at 200 mg kg^-1 in reducing the oviposition rates of C maculatus at various storage intervals up to 8 months post-treatment. However, teflubenzuron reduced adult emergence (F1 progeny), achieving control ranging from 96.2% at 1 month to 94.3% at 8 months. Hexaflumuron showed a similar trend in its residual activity, ranging between 93.8% control at 1 month to 88.2% control at 8 months post-treatment. However, pyriproxyfen was more active than the CSIs tested and caused complete suppression (100% control) of adult emergence at all storage intervals. Unlike the IGRs tested, pirimiphos-methyl applied at 25 mg kg^-1 was more effective in reducing oviposition rates of C maculatus up to 8 months post-treatment. A strong reduction of adult emergence was also observed at various bimonthly intervals (98.6% control at 1 month to 91.6% control at 8 months post-treatment). The persistence of hexaflumuron and pirimiphos-methyl in cowpea seeds was also studied over a period of 8 months. The loss of hexaflumuron residue in treated cowpeas (200 mg kg^-1) was very slow during the first month post-treatment (4.43%). At the end of 8 months, the residue level had declined significantly to 46.4% of the initial applied rate. The loss of pirimiphos-methyl residue in treated cowpeas (25 mg kg^-1) was relatively high during the first month post-treatment (36.7%) and increased to 81.6% after 8 months. Copyright © 2003 Society of Chemical Industry

Keywords: Callosobruchus maculatus; insect growth regulators; OP; pirimiphos-methyl; ovicidal activity; residual activity; persistence; cowpea seeds

Document Type: Research article

DOI: http://dx.doi.org/10.1002/ps.783

Affiliations: 1: Department of Pesticides, Faculty of Agriculture, Menoufiya University, Shebin El-Kom, Egypt 2: Plant Protection Institute, ARC, Dokki, Egypt 3: Central Agricultural Pesticides Laboratory, ARC, Dokki Egypt

Publication date: 2004-01-01

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Persistence and residual activity of an organophosphate, pirimiphos-methyl, and three IGRs, hexaflumuron, teflubenzuron and pyriproxyfen, against the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae)

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