Effect of Apple Root Sucker, on Density and Dispersal of Spider and Predatory Mites

Abstract

The results from Perry apple orchard (in northern Utah, 1992) show that the spider mites could migrate from ground vegetation through tree root sucker, tree trunk, and then into tree canopy. Leaves of root sucker let the overwintering spider mite establish their first population there, and did appear to contribute to the higher spider mite densities in tree canopy The total percentage of spider mites was found higher and the relative density of total predatory mites was found lower in treatments with root suckers. The movement in mid-July and outbreak in early August of mites might be due to disturbed cultivation on ground covers. In addition, the score method used in this experiment could give the similar population density estimates. 依1992年在北猶他蘋果園所作之調查，顯示葉蟎之族群可從地上植被經由樹基之吸芽及樹幹，然後遷移至樹冠之葉片上。位於樹基之吸芽葉片，能提供越冬蟎類於春天開始活動時之棲所與取食需求，進而造成以後樹上蟎類的大發生。整體而言，在留有吸芽之樹上，可發現較高比率之葉蟎數，而其捕食蟎之密度相對較低。在7月中旬之蟎類大發生與大遷移，可能與地面植被之耕培行為有關。另外， 在本試驗中所使用之積分估算法，能相當準確的估算蟎數。