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Subject: Entomology × Author: Betty Varghese × Author: KAU × End date: 2009 × Start date: 2000 ×
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    ThesisItemOpen Access
    Evaluation of newer insecticides against major pests of cowpea Vigna unguiculata (L.) Walp and their effect on natural enemies
    (Department of Entomology, College of Agriculture, Vellayani, 2003) Betty Varghese; KAU; Naseema Beevi, S
    The present study was undertaken to evaluate new insecticides against the major pests of cowpea in the laboratory, to study the effect of promising chemicals on the natural enemies and to assess their bioefficacy in the field. The insecticides selected were imidacloprid (0.025%), acetamiprid (0.002%), diafenthiuron (0.05%), fenazaquin (0.05%), profenofos (0.05%), triazophos (0.05%), chlorpyrifos (0.05%) and acephate (0.05%). Malathion (0.1 %) was used as the check. The pea aphid (Aphis craccivora Koch.), the leaf caterpillar (Spodoptera litura (FB.), the pod bug (Riptortus pedestris Fb.), the spotted-pod-borer (Maruca vitrata (Fabricius) and the pod caterpillar (Lampides boeticus Linn.) were the pests selected for laboratory studies. Cowpea plants were sprayed with insecticides and the test insects of uniform stage were released on the sprayed plant parts cut at different intervals. Chlorpyrifos, profenofos, triazophos, acetamiprid, imidacloprid and acephate proved effective against the pea aphids. Chlorpyrifos, profenofos and triazophos gave higher mortality of S. litura. The chemicals found superior against the pod bug, R pedestris were chI orpyri fos, acephate, profenofos and imidacloprid. Against M vitrata, chlorpyrifos, acetamiprid, triazophos, acephate and profenofos gave higher mortality. The insecticides that were superior against L. boeticus in the laboratory were chlorpyrifos, acetamiprid, triazophos, acephate and profenofos. The toxicity of promising insecticides on the predators (Chrysoperla carnea (Stephens), Menochilus sexmaculatus (Fb) and Coccinella transversalis Fab.) and parasitoids (Chrysocharis johnsoni Rao and Apanteles taragamae Vier) were studied following dry film technique. LC50 values were calculated following probit analysis. Chlorpyrifos and profenofos were more toxic to the larvae of chrysopid, C. camea and the coccinellids, M sexmaculatus and C. transversalis than triazophos, acephate, acetamiprid and imidacloprid. Chlorpyrifos, triazophos, profenofos and malathion were more toxic to the parasitoids, A. taragamae and C. johnsoni than to the chrysopid and coccinellid predators. The compatibility of insecticides with the entomopathogen Fusarium pallidoroseum (Cooke) Sacc. was studied following poisoned food technique. Among the chemicals found promising against aphids, acephate, acetamiprid and imidacloprid were compatible with the entornopathogen, F pallidoroseum. But profenofos completely inhibited the growth whereas chlorpyrifos and triazophos showed partial inhibition In the field experiment chlorpyrifos, profenofos, acetamiprid, imidacloprid, acephate and triazophos gave greater reduction in aphid poulation. Acetarniprid treated plots recorded more number of predators followed by imidacloprid indicating the safety of neonicotinoids than the other insecticides like chlorpyrifos, malathion, diafenthiuron, profenofos. triazophos and acephate. Insecticides found effective against pod borers under field condition were chlorpyrifos, acetamiprid, acephate and profenofos. Acephate, chlorpyrifos, imidacloprid, profenofos and acetarniprid were found effective against pod bugs in the field trial. Greater grain yield was obtained from plots treated with acephate, chlorpyrifos, acetamiprid, profenofos and imidacloprid. However the safety to these chemicals in terms of the persistence of residues in the pods may be further studied before making recommendation in IPM programme.