Sometimes, when the land is too weedy the crop is abandoned. The demands of transplanting and manual weeding, and increasing shortages of labor, have encouraged the move to direct seeding in rrigated and rainfed lowlands. Weeds become a major issue in these systems because rice and weeds emerge at the same time, and weed control by flooding is difficult in seedling rice. Some are herbivores that feed on the rice plant, others are parasitic disease organisms. Although only a few pest species cause sufficient yield reductions to require intensive control measures, they are frequently cited as major constraints to rice production.
Actual losses are much lower.
But considering the myriad opportunities for pest-crop interactions, such outbreaks can be considered as rare events. When these outbreaks occur, however, farmers suffer substantial economic losses. BPH destroyed 200,000 ha of rice between 1975 and 1980. In Indonesia, a virus disease destroyed 100,000 ha between 1972 and 1975 in South Sulawesi alone. In the early 1900s, ricefield insects and diseases caused widespread famine in Japan and China.