MSc

Bio efficacy of natural organic materials was evaluated by field experiment at Agricultural Research Station, Mannuthy, 2003-04 against major insect pests of rice. A popular variety ‘Jyothi’ released by RARS, Pattambi was used for the study. Leaves of different plant species like mango (Mangifera indica), cashew (Anacardium occidentale), garadi (Cleistanthus collinus), snake wood (Strychnos nux-vomica), glycosmis (Glycosmis pentaphylla), glyricidia (Glyricidia maculata) leaves and cowdung (5 t ha-1) were incorporated into the field two weeks prior to transplanting. The organic sprays viz., karanj (Pongamia pinnata) oil (2%), hydnocarpus (Hydnocarpus laurifolia) oil (2%) and cow’s urine + asafoetida (Ferula foetida) (20ml + 20g L-1) were sprayed at three critical stages of crop growth (i.e, active tillering stage, maximum tillering stage and milky stage). The effect of these treatment combinations was compared with chemical insecticides, which were recommended by Package of Practices Recommendations of KAU. The salient findings are abstracted below.

The present investigation revealed that the most effective treatment combinations against stem borer were snake wood + hydnocarpus oil and snake wood + karanj oil. It was found as effective as chemical treatment carbofuran (@0.75 kg ai ha-1). The effect of snake wood + hydnocarpus oil and garadi + karanj oil was similar to that of carbaryl (0.3%) in the control of leaf folder. The chemical insecticide Methyl parathion (0.2%)gave the highest control over rice bug infestation. The treatment combinations mango + karanj oil, mango + hydnocarpus oil, mango + cow’s urine-asafoetida, and snake wood + hydnocarpus oil exhibited effective control over the population of rice bug. Population of natural enemies was high in botanical treated plots as compared to chemical treated plots.

Treatment combination, garadi + karanj oil gave the highest control on sheath rot disease of rice. Glyricidia + cow’s urine–asafoetida treated plots recorded the lowest incidence of brown spot. Studies on the effect of treatments on weed population showed that combination of snake wood and hydnocarpus oil was the best treatment. Better plant height and maximum number of tillers was observed in glyricidia + hydnocarpus oil treated plots. Different treatment combinations showed similar effect on test weight of seeds. Glyricidia + hydnocarpus oil treated plots gave higher number of panicles per hill, whereas mango + hydnocarpus oil applied plots recorded the highest per cent of filled grains. The highest grain yield of rice crop was recorded in glyricidia + hydnocarpus oil treated plot (3152 kg ha-1). Highest grain : straw ratio was noticed in garadi + karanj oil applied plots followed by snake wood + hydnocarpus oil.

The results show the importance of organic materials for the suppression of pests of rice and also their efficacy in preserving the natural ecosystem. In the present scenario of sustainable agriculture, use of natural organic materials requires special attention, as they are ecofriendly and farmer friendly.