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褐飞虱(NilaparvatalugensStal)和白背飞虱(SogatelafurciferaHorvath)是我国水稻的两种重要迁飞性害虫,主要虫源皆来自亚洲中南半岛;最初的虫源地在湄公河三角洲,直接迁出地为红河三角洲。湄公河三角洲地处热带,全年各月平均气温25~28℃;月降雨量悬殊,旱季(11~4月)可数月滴水不落,雨季(5~10月)若月降雨量超过200mm即成洪涝。红河三角洲地处亚热带,3~4月常受我国冷空气的影响。这两种热带性害虫,适宜取食和繁殖的温度下限为22℃,正与它们的迁入主峰降落地带的月平均气温巧合。对褐飞虱不利的为洪涝而对白背虱不利的为干旱。在湄公河三角洲,9~10月若出现洪涝,来年褐飞虱将不致成灾,若无洪涝即可猖獗。11~12月的月降雨量超过90mm,来年白背飞虱将猖獗而且对褐飞虱也有利;若酷旱则两种飞虱都将受到抑制。在红河三角洲,当月平均气温3月低于20℃或4月低于22℃都将使两种飞虱的迁入期延迟约半个月,尤其4月的低温还可使两者在迁入我国之前少繁殖1代。
Nilaparvata lugens Stal and Sogatelafurcifera Horvath are two important migratory pests of rice in China. The main insect pests are all from the Indochinese Indochinese Peninsula. The primary source of the insects is the Mekong Delta, which is the red river delta. The Mekong Delta is located in the tropics. The annual average temperature is 25-28 ℃ throughout the year. Monthly rainfall is poor. In dry season (11-4 months), drip can not fall for several months. If monthly rainfall exceeds 200mm in May to October Into flood waterlogging. Red River Delta is located in the subtropical, 3 to 4 months often affected by the impact of cold air in our country. The two tropical pests, suitable for feeding and breeding temperature limit of 22 ° C, is coinciding with the monthly average temperature of their main peak drop zone coincides. Detrimental to the brown planthopper, it is droughty for the flood but for the white-backed lice. In the Mekong Delta, if floods occur between September and October, the Nilariporum will not cause disaster in the coming year, and rampant will be possible without floods. The monthly rainfall from November to December exceeds 90 mm. In the coming year, the white -backed planthopper will be rampant and also beneficial to the brown planthopper. In the case of cool drought, both planthoppers will be suppressed. In the Red River Delta, if the average temperature of the month is below 20 ℃ in March or below 22 ℃ in April, the migration period of the two planthoppers will be delayed by about half a month. In particular, the low temperature in April will allow both to move in Less breeding in China before 1 generation.