Plants grown under physicochemicai stresses frequently become more susceptible to insects. We determined the effects of salinity stress at 1.0 and 1.2 S/m electrical conductivity on the magnitude and expression of resistance of rice (Oryza sativa L.) cultivars to So&atella furcifera (Horv~th) under glasshouse conditions using natural daylight of 12 h, 29/21 °C (day/night), and minimum 70% relative humidity. Salinity stress increased N, decreased K, and decreased the quantity of allelochemicals extracted as steam distillates from rice plants. Intake and assimilation of food, growth, adult longevity, fecundity, and population increase of the insect were significantly greater on plants grown at salinity level of 1.2 S/m than on unstressed control plants. Regardless of the level of stress, the difference between susceptibility of 'Taichung Native 1' (TN1) and resistance of 'IR2035-117-3' (IR2035) cultivars remained distinct. Painting of steam-distillate extract of resistant IR2035 plants on susceptible TNI plants made them less attractive and decreased food intake and assimilation by S. furclfera. In contrast, intake and assimilation of food increased significantly on IR2035 plants painted with TNI extract. Effects of physicochemical stresses, such as salinity, must be considered when breeding insect-resistant rice cultivats for salinity-prone areas. R ICE IS CULTIVATED under diverse climatic, hydrological, and edaphic conditions. The stability of rice production frequently is threatened by increases in pest incidence and the prevalence of physicochemical stresses, including salinity. Several species of insects affect the rice crop in South and Southeast Asia. Of these, the whitebacked planthopper is a major pest in Fiji, Japan, Korea, Vietnam, Thailand, India, and Pakistan (Khan and Saxena, 1986a). Under favorable conditions, the insect produces several generations per crop and inflicts heavy damage due to hopperburn (Pathak, 1968). In South and Southeast Asia, nearly 60 million ha of land are affected by salinity ranging from 0.4 to 1.8 S/m (Akbar, 1986). Higher levels of salinity are a major obstacle to high-grain yields on about 27 million ha of land in deltas, estuaries, and coastal fringes in Asia. These areas are physiographically and climatically suited to rice production, but grain yield is reduced drastically at salinity level of 1.0 S/re. Highyielding, semidwarf cultivars, which lack tolerance to salinity, are grown in inland saline areas, but lowyielding, salt-tolerant, traditional, tall 'indica' rices with long growth duration are cultivated in coastal saline environments (Akbar, 1987).
