農藥引起柑桔葉蟎再崛起現象之觀察

Abstract

自1950年代開始密集使用農藥防治柑桔病蟲害後，柑桔葉蟎已成為柑桔之重要害蟎，而天敵遭殺滅被認為是其發生崛起之主因。本研究即在觀察藥劑使用後，葉蟎在天敵影響較少之網室內，及野外田問棲群產生再崛起之現象。結果顯示在推薦濃度下，以加保利、甲基巴拉松、加保扶及馬拉松等藥劑處理者，均能促使柑桔葉蟎產生極顯著之再崛起現象。而波爾多、乙基巴拉松、撲滅松、大滅松及萬靈等處理，亦能促使葉蟎產生顯著增殖之現象。 施藥之次數與間隔，為影響此蟎大發生之主要因素。單次施藥促使此蟎蟎之增殖不明顯，若間隔21天再施藥一次，則施後一週其棲群密度便已顯著增高。然而每週施藥一次共施四次時，則此葉蟎之增殖更形猖獗。 另外，撲滅松等殺蟲劑在田間處理對葉蟎之增殖情形較網室者為顯著，故農藥殺滅天敵亦可能為促使此蟎再崛起之重要因素。 The citrus red mite, Panonychus citri (McGregor) has been one of important pests of citrus since intensive use of pesticides for controlling the insect pests and diseases of this crop in the years of 1950. Destruction of natural enemies was considered as the major factor inducing severe infestation of the mite. Present study was conducted to observe the nature of mite resurgence following pesticide applications both in a wirehouse. (natural enemies free) and field conditions. The results showed that the population of the mite increased significantly following the application of insecticides, such as 85% Carbaryl W. P., 50% Methyl parathion E. C., 40.64% Furadan F., 50% Malathion E. C., 4-4 Bordeaux Mixture, 47% Ethyl parathion E. C., 50% Sumithion E. C., 44% Dimethoate E. C., and 24% Lannate S. in their recommended cncentration. Among them, Carbaryl, Methyl parathion, Furadan, and Malathion induced a more severe outbreak of the mite than the others. Time and interval of pesticide application were the important factors affecting an outbreak of the mite. Single application of pesticide did not increase the mite population significantly. Two applications with 3 weeks interval increased the population clearly 1 week following the second spray, whereas four applications with 1 week interval induced a severe outbreak of the mite. On the other hand, the insecticides such as Sumithion which was observed to increase a greater mite population in the field than that was tested in the wirehouse conditions. Therefore, destruction of nature enemies was also an important factor in causing a resurgence of the mite.