Efficacy of Wild Rice Extracts, Oryza officinalis Wall and O. punctata Kotschy for Controlling Brown Planthopper, Nilaparvata lugens (Stål)

Abstract

The National Rice Seed Storage Laboratory for Genetic Resources, Rice Department has collected wild rice varieties in Thailand, as a database collection for increasing productivity and utilization. The wild rice leaves contain bioactive compounds that can affect brown planthopper (BPH), an important rice insect pest in paddy fields. This research aimed to analyze of wild rice extract bioactive compound and to test the efficacy of wild rice extract for preventing and eliminating BPH i.e., repellent efficacy test, effects on inhibiting food intake, effects on the number of BPH nymph. In addition, the study of appropriate timing and concentration rate of wild rice extract were also observed. The results showed that some chemicals have been reported as larvicidal activity such as acetic neophytadiene, phytol, stigmasterol and dibutyl phthalate. Testing the efficacy of wild rice extract of Oryza officinalis had the highest repellent efficiency at 72.50 and 68.75% after 24 and 48 hours of spraying treatment respectively. The wild rice extract of O. punctata was able to inhibit BPH feeding and the amount of honeydew was 9.67 mg. Spraying both varieties of wild rice extracts on different rice varieties had different effects on the increasing of BPH nymph compared with distilled water treatment, especially when spraying wild rice extracts on PTB33 and Pathum Thani 1 (PTT1) which found lower number of BPH nymphs when compared to spraying on Taichung Native 1 and RD43. The optimum spraying period was every 15 days with 10% concentration rate. This study can be concluded that wild rice extract can be used as an alternative safe method for preventing and eliminating BPH, reducing the use of chemicals, and increasing value addition on wild rice varieties found in Thailand.