鳳梨粉介殼虫（Dysmicoccusbreoipes(Ckll.)）防治試驗

Malathion 50% EC and Aldrex-2 were both used for controlling the mealybug (Dysmicoccus brevlpes Ckll.) and ants respectively. Effective control of mealybug was obtained excellently by dipping the pineapple slips into malathion for 2 minutes at the concentration of 0.1% before planting. There were almost none of mealybugs found for as long as four to five months after the pineapple planted. It is the essential factor that if the pineapples were infested by mass colonies of mealybugs in the earlier months after planting, wilt would occur seriously in the early stage of the growing plants. Aldrex-2 was diluted into 100 times with water and sprayed at the rate of 4 kgs active ingredient per hectare on the soil surface of pineapple field for every three months. Ants control also gave the constant influence of reducing the mealybug population, however, gocd results of reducing the ants population were not gained obviously until the beginning of rainy season, during which pineapples were growing more rapidly. Shorter intervals of malathion applications during the early stage of growing pineapples revealed better results of mealybugs control than that of the treatments of longer intervals of applicaticns. 一、本試驗歷時三年完成，對於粉介殼蟲之防治，由各處理之調查結果，在鳳梨定植後八個月內，以浸苗之效果最為顯著，以後由於田間粉介般蟲之口漸傳佈，其成效顯因時間之延長而漸趨低落，但在定植後八個月左右粉介殼蟲蟲口密度之高低，對新植梂萎凋病發病程度，有顯著之決定作用。 二、防蟻之效果在最初七，八個月左右，並無顯著之成效，但自此以後若繼續施藥，其效果為諸處理中最顯著者，且隨時間之延長其效益彰。 三、灌藥次數多寡，其效果雖亦有差異，惟在不防蟻區較為顯著，一般以灌藥三次並加防蟻，其效果與單獨灌藥五次者並無顯著差異。至殺蟲劑之濃度以馬拉松（Malathion EC）之有效成份0.1 ％較0.05％為優。 四、粉介殼蟲之蟲口密度，雖因受氣候之影饗而有高舉現象，但鳳梨之生長情形亦可左右其密度。例如在鳳梨之新植株上，粉介殼蟲之棲息部位僅局限根部及靠近地面之基部，所以在雨期其蟲口密度易受降雨及土壤水分之影響而急劇下降，至雨期終止後其密度復漸增高。但在鳳梨之宿根株，粉介殼蟲之密度在雨期雖略受影響，但不若新植株上所受影響之甚，其原因可能係粉介般蟲在宿根株上棲息之位置離地面較高，而鳳梨植株亦較高大，植株之葉相互交錯，使粉介殼蟲有較多隱蔽之處，而免受雨水沖失或浸死之患。 五、螞蟻週年發生之消長，受氣溫之影響較為顯著，即在高溫時其密度甚高，在一，二月低溫期則趨下降，但為時甚暫。惟螞蟻發生密度受鳳梨生育之影響亦至鉅，即在鳳梨定植後六，七個月以內，因係在乾旱期，鳳梨發育遲緩，土面為植梂所遮蓋者甚少，而多曝露於陽光之下，所以螞蟻之密度甚低，但雨期來臨之後，鳳梨發育旺盛，葉部將大部份之上面遮蓋，因此螞蟻之密度即隨之而增高