THE RICE BROWN PLANTHOPPER: Feeding Physiology and Host Plant Interactions

Rice, Oryza sativa L., is an ancient cereal crop domesticated about 10,000 years ago along the hilly tracts south of the Himalayas (8). Because of the long history of its cultivation and its widespread dispersal, rice is probably the most genetically diversified among the world's cereal crops. In all Asian countries, rice is by far the most important staple food crop, and approxi­ mately half of the people on earth obtain the majority of their caloric intake from rice. Among the rice herbivorous insects, the brown planthopper, Nilaparvata lugens (Stal) (hereafter BPH), is one of the most notorious pests. It causes economic damage to the rice crop directly by feeding ( 116) and also indi­ rectly by transmitting grassy stunt (8 1) and ragged stunt virus diseases (54). The BPH is a small (2-3.5 mm in body length), brownish, sucking insect, belonging to the suborder Homoptera, series Auchenorrhyncha, super­ family Fulgoridae, and family Delphacidae. Members of the genus Nilapar­ vata are characterized by several lateral spines on the hind basi-tarsus (69). The adult shows density-dependent wing dimorphism with macropterous and brachypterous forms (20). Macropterous adults have the ability to migrate over long distances. The BPH is endemic to the tropical oriental region, but its habitat can temporarily expand as far north as Japan and Korea every summer through long-distance massive migrations from the tropics (46). The BPH is a monophagous insect restricted to cultivated rice and its allied wild forms such as Oryza perennis and O. spontanea (45). Thus, the seasonal occurrence and relative abundance of the BPH depend largely upon cropping patterns and intensification of rice cultivation.