苹果园混合覆盖植物对害螨和东亚小花蝽的影响

苹果园种植紫花苜蓿，为捕食性天敌提供了适宜的生存环境和补充猎物，使苹果园天敌数量增加，叶螨种群下降。夏至草是苹果园杂草的优势种，该杂草可提供天敌生存所需的花粉、花蜜和猎物，使东亚小花蝽发生时间提早，发育速度加快。在６月中旬前，东亚小花蝽可在夏至草上完成２代，在紫花苜蓿上完成１代。夏至草与紫花苜蓿的比例变化影响苹果园节肢动物物种数量，当混合植被中夏至草的覆盖度大于２５％时，对覆盖植物和苹果树冠捕食性天敌种群数量最为有利。夏至草与紫花苜蓿混合（１∶４），比单一紫花苜蓿上天敌的数量增加２～３倍，苹果树冠天敌数量增加７０％，苹果叶螨种群数量降低３０％

EFFECT OF THE COVER CROPS ON THE PEST MITE PANONYCHUS ULMI AND ITS PREDATOR ORIUS SAUTERI

Alfalfa was planted between the rows of apple trees with a view to providing eno ugh foods and/or better habitats for mite predators. it was found that the numbe r of natural enemies was increased and that of pest mites decreased. The white f lowered lagopsis is a dominant weed species in apple orchard. Orius sauteri occurred earlier and developed faster at the presence of the white flowered lago pss as the latter can provide enough pollen, nectar and prey as foods. Before mi d June, Orius sauteri developed 2 generations in the presence of the white flowered lagopsis, whereas only 1 generation was developed by planting alfalfa. The density of predator on the cover crop as well as on the apple trees increase d when the coverage of white flowered lagopsis was more than 25% in the orchards , the number of predator on the cover crops were 2 to 3 times and 70% increased on the apple trees in the orchard with both alfalfa and white flowered lagopsis (1:4) than that in the orchard with alfalfa alone.