COMPARATIVE TOXICITY OF PESTICIDES TO NATURAL ENEMIES OF CALIFORNIA RED SCALE, Aonidiella aurantii (Maskell)

A KRISHNAMOORTHY, D RAJAGOPAL

Abstract


Several pesticides commonly used on citrus and rose were screened for their toxicity to four important natural enemies of the California red scale viz., Aphytis melinus DeBach, Chilocorus nigrita (F.), Pharoscymnus horni (Weisman) and Eryngiopus sp. The natural enemies were exposed to pesticides treated leaf surface on the day of application and subsequently at 7 days interval to determine the immediate and the residual toxicities. Botanical insecticides, viz., neem oil, pongamia oil and mahua oil; acaricides, viz.; dicofol and sulphur and fungicides, vrz., copper oxychloride and maneb were safer to A. melinus, C. nigrita and P. horni whereas, acaricides were toxic to the predatory mite Eryngiopus sp. Among eleven insecticides tested, chlorpyrifos and dichlorvos were alone found to be comparatively less toxic inflicting 60 and 73.3% mortality, respectively, at 24h exposure to adults of A. melinus. Other insecticides were highly toxic inflicting 100% adult mortality to all the predators. Residues of dichlorvos and chlorpyrifos were alone observed to be totally non-toxic among the toxic insecticides 7 and 21 days after treatment (DAT), respecti vely. The toxic effects of other insecticides persisted for more than 28 DAT.


Keywords


Aonidiella aurantii;Aphytis melinus;California red scale;Chilocorus nigrita;Eryngiopus sp.;Pharoscymnus horni;toxicity

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