| Popis: |
Rice is cultivated on about 2,000,000 ha of land, and its production is by far the largest among all crops in Japan. One of the most serious rice pests in Japan was the rice stem borer, Chilo suppressalis, whose population density has begun to decrease rapidly since the early 1970s (Hirai 1994). Consequently the insect has become a minor and local pest. On the other hand, outbreaks of the rice leaffolder, Cnaphalocrocis medinalis, have increased in frequency since the late 1960s, and therefore this insect has now become one of the major rice pests (Wada and Kobayashi 1980). The brown planthopper, Nilaparvata lugens, is also one of the major rice pests in Japan. Since ancient times there have been numerous records of brown planthopper outbreaks, which sometimes have caused severe famine (Dyck and Thomas 1979). |
