The insecticidal activities of 27 different commercial products with environmentally friendly organic material (EFOM) against Scotinophara lurida, a major rice pest, were evaluated in the laboratory using spraying methods on plants and insects. Seven plant-derived organic farming materials (EFOM-8, -10, -12, -13, -19, -20, and -26) with high insecticidal effects when sprayed directly on the insect’s body rather than on the plant were selected. In the indoor rice pot test, all 7 EFOMs showed an insecticidal rate of over 73.3% under irrigated conditions. Notably, EFOM-13 and EFOM-20 demonstrated much higher insecticidal rates, ranging from 1.5 to 1.8 times, in irrigated conditions compared to drained conditions. In the semi-paddy field test, EFOM-10 (80% garlic extract), EFOM- 13 (62% neem extract), and EFOM-26 (70% sophora extract+28% ethyl alcohol+2% pyrethrum extract) exhibited a higher control value of 88.9% in the irrigated paddy on the 7th day, surpassing the control values in the drained paddy by 1.4 to 1.9 times. The control value in the irrigated rice paddy field sprayed with EFOM-10 reached 86.2% on the 7th day, which was 1.4 times higher than 61.9% in the drained paddy. Taken together, the findings suggest that direct contact of the insect’s body with sufficient amounts of spray solution and the maintenance of paddy irrigation can enhance the controlling effect of EFOMs. These findings will be valuable in developing an optimal S. luridacontrol strategy for application in rice paddy fields in the near future.

Scotinophara lurida is one of major sap-sucking pests in an organic rice farming paddy fields in Korea. Several Poaceae grasses (e.g, rice, barley etc) have been known as a host plant. To find out a true host plant of S. lurida, the developmental characteristics such as weight gain and developmental duration were checked on total eight grasses species including rice and corn. In the results, weight of the fifth nymphal stage was the highest value in the barnyard millet and rice plant. In addition, nymphal duration was the shortest value in the barnyard millet and rice plant. But, in corn and common millet plant, S. lurida nymphs could not complete the development to the adult stage. These results suggest that six Poaceae grasses including rice and barnyard millet out of eight test grasses are close related to true host plants of S. lurida.

Because Scotinophara lurida has the habit of living under the rice plant, an introduction of a method for efficient control when spraying eco-friendly organic materials is needed. In this study, we investigated the density of S. lurida in drained- and irrigated-paddy field after spraying an organic material containing garlic bulb extracts, which has high insecticidal activity in S. lurida in direct spraying test in glass tube. As a result, an irrigated rice paddy showed a control effect of 66.4% after 3 days of spraying and 86.2% after 7 days, while a drained rice paddy showed a control effect of 33.9% after spraying and 61.9% after 7 days. These results suggest that effective control can be achieved in irrigated rice fields if organic farming materials are evenly sprayed and reach to the body of S. lurida. It is remained to study how irrigated water do contribute to increase the insecticidal effect in the future.