稻細蟎之發生與氣象關係及其防治研究

Abstract

稻細蟎因水稻不稔症于民國65年突然大發生，而被指認是造成不稔症的主因以來。依據調去，每年發生既普遍，密度又很高，然于68年卻普遍減低，且不稔症發生的面積也僅限于局部某些地區，其原因何在，尚無資料可尋。本場于67年開始從事稻細蟎的發生與水稻揮秧期別及氣象因子關係調查，發現67、68兩年之氣象因子有所不同，是否與稻細蟎之發生有關，頗值檢討。又稻細蟎的越冬與藥劑防治結果亦一併報告之。 依據試驗田附近設立氣象站之資料顯示，67年4月中旬至6月中旬平均氣溫較68年約高2~3℃，67年的全年相對濕度也較68年高，尤其在4月下旬至7月下旬正是稻細蟎開始發生的時機，兩年之相對濕度在此期間相差更為顯著。至於兩年之降雨量情形也有差異，即67年的梅雨期及雨季都比68年早，雨量也較豐富。 稻細蟎至目前為止，尚未發現有其他寄主，二期作水稻收割後，尚能繼續生存於未收穫之活稻株至翌年2月，在越冬期問均可發現卵、幼蟎及成活蟎。然而附近雖種有秧苗，但仍未發現有遷移至秧苗上。空氣中稻細蟎的初期發現，67年為5月初，68年則在5月底。而稻株上的稻細蟎約在空氣中測到後1個半月才被發現。 由於今年（68）稻細蟎密度太低，供試5種藥劑間無顯著差異，但仍以47%乙基巴拉松乳劑效果最佳，其次是50%甲基巴拉松乳劑。至於防治適期試驗，因于水稻抽穗時正遭颱風侵襲，因風害而無法調查稔實率。但從稻細蟎防治情形看，在水稻孕穗期開始施用47%乙基巴拉松乳劑1000倍，而後隔14天再施藥1次，將可抑制稻細蟎密度的增高。 Since 1976, because of the abrupt occurrence of rice sterility, the rice tarsonemid mite (Steneotarsonemus spinki) was recognized as the main factor causing rice sterility. According to the investigation, the annual population was usually very high since then. However, the population declined and the rice sterility occurred only limited in some areas in 1979. The reason remained unknown. In 1978, an investigation was made to detect the relationship between the occurrence of rice tarsonemid mite, rice transplanting stages, and meteorological factors. It was found that the meteorological factors were different in 1978 and 1979. It was postulated that meteorological factors were probably the main factor influening the occurrence of tarsonemid mite. According to the data collected from the meteorological station near the experimental field, it showed that from the middle of April to June in 1978, the average temperature was 2-3℃ higher than that of the same period in 1979. The relative humidity year around in 1978 was also higher than that of 1979. The relative humidity from late April to July, the critical time for the occurrence of tarsonemid mite was particularly different between these two years. The precipitation was also different particularly; the rainy season in 1978 was thus obtained. So far, no other host for rice tarsonemid mite was found. After second crop of rice was harvested, egg, larva or adult tarsonemid mites were found to overwinter on the unharvested living rice plant until the next Feburary, and would not migrate to the nearby rice seedlings. Air-borne rice tarsonemid mites were first found in early May, and were found on rice plants at one and one half month later in 1979. Because of low population of the rice tarsonemid mites in 1979, the effect of five tested chemicals were found not different significantly. However, 47% ethyl parathion E. C. was the most effective, followed 50% methyl parathion E. C. Two applications of 47% ethyl parathion E. C. at the rate rate of 1: 1000 started from the initial booting stage, with 14 days of meterval could effectively inhabit the population increase of rice tarsonemid mite.