Toxicity of diatomaceous earth on seed weevil, Sitophilus oryzae L. and its effect on agro-morphological characters of maize seeds

Sitophilus oryzae L. (Curculionidae; Coleoptera) is considered to be a serious internal feeder of stored cereals. The use of insecticides results in the development of resistance among the pests and residues in the produce. Diatomaceous Earth (DE) is from a natural source, environment-friendly, safe to humans and natural enemies. In addition, it is highly effective against a wide range of stored pest species and has no toxic residues on the treated seeds. The promising alternative to synthetic insecticides is the application of DE in storage pest management under physical control. With this background, the present study was aimed to find the efficacy of DE against rice weevil, S. oryzae L. and their effect on the agro-morphological characters of maize (Zea mays L.) seeds. Contact toxicity bioassays were carried out with different concentrations of DE against S. oryzae. The results of the bioassay studies revealed LD50 at the concentration of 1.27 mg/100 gm of maize seeds. Further, 100 per cent mortality was achieved at the dose of 15 mg/100 gm of maize seeds within six days of exposure. The effect of DE on the germination provided a significant increase in germinability of maize seeds (LD50= 94%, LD95= 98% and control= 96%). DE at the concentration of LD95 had a beneficial effect on the seedling parameters, especially germination% (98%) and seedling length (53.02 cm) of maize. The present study concluded that DE could be effectively utilised as an alternative management tool to chemical insecticides in the management of rice weevil under storage conditions