果苔螨在乾县北部的发生及药剂防治试验

Occurence of Brown Mite and Test of Its Chemical Control In North part of Qianxian County

果苔螨是渭北旱塬果区的偶发性螨类,1991年在乾县北部严重发生,苹果园受害株率73％。果苔螨一年发生4～6代,以卵在果树主、侧枝阴面、叶痕、剪锯口、果台等处越冬。越冬卵于4月下旬达孵化盛期,5月上中旬成螨大量发生,主要分布于树冠内膛。6,7月份是全年为害的严重时期。于越冬成螨期喷药可有效压低螨口密度,药剂可用20％灭扫利2500～4000倍液、2.5％功夫2000倍液,40％氧乐果3000倍液及40％乐果2000倍液,防效均在90％以上。

The brown mite,Bryobia rubrioculus (Scheuten), is a sporadic pest in orchardson the arid plain. In 1991, the occurence of brown mite was very serious in the northernpart of Qianxian County. Concenquently, 73% of apple orchards were seriously affected.The mite completes four to six generations a year, and overwinters as eggs in the shade sideof branches, leaf marks, pruning wounds, fruit support, etc. The hatching peak of theoverwintered eggs is late in April, The adult mites are abundant in early to middle May.mainly in the inner part of canopy. June and July are the seriously damaging season. Appli-cations of chemicals can effectively suppress the mite population densities. For the chemi-cals, we can choose 20% of fenpropathrin (Meothrin X 2 500 to 4 000), 2.5% of cy-halothrin (Kung Fu, X 2 000), 40% of omethoate (Folimat, X 3 000), or 40% of di-amethoate (Rogor, X 2 000). The control efficiency of all the chemicals was over 90%.