稻田小氣候與稻飛蝨發生關係之觀察

Abstract

一、五十八年第二期作及五十九年第一期作在臺北測量稻田中之水溫，稻株間水面以上垂直高度10、30、60及90公分處之溫度及濕度，並參照大氣之降雨量及氣溫資料，分析稻株間小氣候與稻飛蝨發生之關係。二、在稻株間之溫度一般顯較大氣溫為高，在稻株近水面10公分處及水溫，較其它各層小氣溫稍低，尤以在第二期較有現則，此現象可能受稻株生長茂盛覆蓋田面所致。三、第二期作稻株間之相對濕度分佈頗有規律，在近水面10公分處均較高，並順垂直高度而漸次降低。四、第二期作稻株間近水面10公分，由於稻株覆蓋而形成高溫多濕又日照少之特殊環境，故稻飛蝨常在此生境條件下生殖猖獗為害。五、本觀察期間僅兩期作水稻，在調查稻田中之稻飛蝨發生密度均極低，而卵寄生蜂之發生密度頗高，或由於卵寄生蜂抑制關係，故對此問題尚有待較長期觀察。 1. The survey hereby reported was carried out in Taipei in 1969 (2nd crop) and 1970 (1st crop). The air temperature and relative humidity reading were taken at 4 different niches (10, 30, 60 and 90 cm above water surface in the paddy field) between “hills” of the rice plant. For comparison, the rainfall, the air temperature in the open, the water temperature in the field, and the population density of the rice plant hoppers were also kept on record. 2. As a rule, the air temperature between the rice-hills was significantly higher than that in the open, and in generally, the temperature of the air near the water surface and that of the water were slightly- lower than at higher niches. The latter became more significant in the later parts of the growing season, because the rice foliage was then more prolific and formed an effective shade. 3. The relative humidity was highest near the water surface and decreased successively on approaching the open and the top of the rice plant. This phenonienon was particularly apparent in the 2nd crop. 4. Theoretically, the optimum niche for the breeding and multiplication of the rice plant hoppers is at the level of about 10 cm above the water surface, where both the temperature and relative humidity are high and the shade formed by rice foliage is most effective. On the other hand, as a result of accumulating population density of the rice plant hoppers, the outbreaks of these insect pests occurs usually in the 2nd crop. 5. During the two growing seasons under observation, the population density of the rice plant hoppers was very low while that of the egg-parasites, fairly high. It is suggested that further field surveys should be undertaken when the population density of the former is high, and that the population dynamics and ecological requirements of the egg-parasites should be investigated.