Persistence and residual activity of an organophosphate, pirimiphos-methyl, and three IGRs, hexaflumuron, teflubenzuron and pyriproxyfen, against the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae).
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.
Abo-Elghar
Gamal E
GE
Department of Pesticides, Faculty of Agriculture, Menoufiya University, Shebin El-Kom, Egypt. aboelghar.gamal@hotmail.com
El-Sheikh
Anwar E
AE
El-Sayed
Ferial M
FM
El-Maghraby
Hamdi M
HM
El-Zun
Hesham M
HM
D000818:Animals; D001549:Benzamides / Q000378:metabolism / Q000633:toxicity; D001517:Coleoptera / Q000187:drug effects* / Q000254:growth & development; D007887:Fabaceae / Q000469:parasitology; D005260:Female; D007306:Insecticides / Q000378:metabolism* / Q000633:toxicity; D007605:Juvenile Hormones / Q000378:metabolism* / Q000633:toxicity; D008297:Male; D009946:Organothiophosphorus Compounds / Q000378:metabolism* / Q000633:toxicity; D010063:Ovum / Q000187:drug effects; D010573:Pesticide Residues / Q000378:metabolism* / Q000633:toxicity; D010671:Phenylurea Compounds; D011725:Pyridines / Q000378:metabolism / Q000633:toxicity; D005466:Fluorocarbons
D001549:Benzamides; D007306:Insecticides; D007605:Juvenile Hormones; D009946:Organothiophosphorus Compounds; D010573:Pesticide Residues; D010671:Phenylurea Compounds; D011725:Pyridines; C014153:pirimiphos methyl; C055613:pyriproxyfen; C058039:hexafluoron; D005466:Fluorocarbons; C052595:teflubenzuron