叶螨为害苹果树的产量损失估测

1987—1989年研究苹果全爪螨(Panonychus ulmi)与山楂叶螨(Tetranychus viennenses)为害对苹果产量的影响。结果表明:①叶螨为害后,叶片的各项生理指标皆有反应,其中以光合作用强度最敏感;②叶螨为害对果实质量无显著影响,但不同螨量的果实体积之间存在明显差异;③平均累积雌成螨螨日(MDi)与平均减产率(Qi)之间有正相关关系,为害当年表现出果实变小单果重减轻,次年表现出花量减少,果实数下降。1987与1989年以苹果全爪螨为主,减产率分别为3.31%—11.25%与2.89%—10.75%。1988年以山楂叶螨为主,减产率为2.36%—13.48%;④上年受害树次年继续测产,看出叶螨的持续影响更为严重。以苹果全爪螨为主的持续减产率第二年达2.0%—86.2%;第三年的影响又相对减轻。以山楂叶螨为主的减产率第二年为-14.4%—69.4%。

EVALUATIONS OF THE DAMAGE OF TWO SPIDER MITE SPECIES TO APPLE TREE

In 1987-1989,the damage of European red mite Panonychus ulmi(Koch)and hawthorn spider mite Tetranychus viennensis Zacher to thephysiology and fruit yield of apple tree were studied.The results wereas follows:1.All the physiological indices of apple leaves were affected bythe damage of the two spider mites,in which the photosynthesis in-tention was most sensitive.2.There was no significant effect of spider mites on the fruitquality,but were obviously different among the fruit sizes damaged bydifferent mite number.3.There was positive correlation between mean accumulated fe-male mite day and mean yield loss rate.The fruits became smaller andlighter,but no decrease in fruit number,in the year that mites dam-aged;while in next year,the effect was expressed as the decreasedflower and fruit number.The yield loss rates in 1987 and 1989 werechiefly caused by the European red mite ranged from 3.31%-11.25% and2.89%-10.75%,respectively;while those in 1988,chiefly due to haw-thorn spider mite,ranged from 2.36%-13.48%.4.The successive mite effects in second year became more severe,the yield loss rate chiefly caused by European red mite ranged from2.0%-86.2%;and those chiefly caused by hawthorn spider mite rangedfrom -14.4%-69.4%.The effects in the third year were alleviated.