MSc

The efficacy of four fungicides and four insecticides alone and in combination was studied at different concentrations recommended, three-fourth and half the recommended concentrations against two major diseases of rice namely, rice blast caused by Pyricularia oryzae Cavara and sheth blight caused by Rhizoctonia solani kahn. And two major insect-pests namely, leaffoldar Cnaphalocrocis medinalis medinalis Guen. And brown planthopper Nilaparvatha lugens stal. At tillering, panicle initiation and flowering stage of the crop. The experiment was conducted in vivo and in vitro conditions during 1989-91, at the college of Horticulture, Vellanikkara, Thrissur.

In general combind application of fungicides and insecticides controlled the diseases and insect-pests more effectively than the treatments given separately.

At tillering stage, a synergistic effect of fungicide was observed, when it was sprayed along with insecticides. Among different combinations tried, tridemorph (o.1 per cent) + monocrotophos (0.0375%) and carbendazim (0.075 ) + guinalphos (0.025 per cent) were the best combinations against blast and sheath blight respectively. In the case of leaffolder and brown planthopper, quinalphos was found to be the best insecticide, when used alone and also in combination with fungicides.

At panicle initiation stage, combined sprays of higher concentrations of carbendazim and monocrotophos was the best combination in controlling both R. solani and N. lugeas. But ediphenphos-phosphamidon combination was found to be the superior against N. lugens.

When combind spraying was given at flowering stage, captafol (0.225 per cent) + quinalphos (0.0375 per cent, and carbendazim (0.075 per cent) + monocrotophos (0.0375 per cent) were found to be the best combinations against P. oryzae and R. solani respectively. But, combination of recommended doses of quinalphos with tridemorph and ediphenphos and, phosalone with ediphenphos were the effective treatments in controlling C. medinalis and N. lugens respectively.

In in vitro studies, a total inhibition of the test organisms, viz.P. oryzae and R. solani were observed in all the treatments. Whereas, in the case of C. medinalis recommended doses of quinalphos in combination with ediphenphos and carbendazim and phosalone with tridemorph recorded highest mortality; while, highest dose of quinalphos with captafol and phosalone with ediphenphos were the superior combinations against N. lugens.

From the above findings it could be concluded that, the fungicides viz. ediphenphos, carbendazim, captafol and tridemorph are compatible with all the four insecticides tried viz. Phosphamidon, quinalphos, phosalone and monocrotophos in controlling the diseases, blast and sheath blight and insect pests leaffolder and brown planthopper.