应用排除法分析两种天敌对桔全爪螨的控制作用

采用排除法，分析桔园中两种主要天敌对桔全爪螨的控制作用。试验表明，在一定益害数量比例条件下，尼氏钝绥螨或深点食螨瓢虫，均可在短期内发挥控制作用，将桔全爪螨种群数量控制在较低的密度。当尼氏钝绥螨：桔全爪螨为１：２０时，１个月后猎物密度从２６头／叶降至１头／叶以下，而对照中则保持在２０头／叶。当深点食螨瓢虫：桔全爪螨为１：２５时，１个月后猎物数量从２９头／叶下降至９．５头／叶。两种天敌共同作用时，猎物

EFFICACY OF AMBLYSEIUS NICHOLSI AND STETH ORUS PUNCTILLUM AS NATURAL ENEMIES OF CITRUS RED MITE

The predaceous mite Amblyseius nicholsi and the lady beetle Stethorus punctillum, are 2 main natural enemies of the citrus red mite, Panonychus citri . Their efficacy were studied in Guizhou province from June to July, 199 1. The results showed that in all three levels of natural enemies/prey ratio, the densities of the prey were suppressed in a short time by either A. michol si or S. pumctillum alone, and decreased dramatically by both predators . When the ratio of the predaceous mite and the lady beetle/the citrus red mit e was 1/20 and 1/25, the densities of the prey decreased from 26 per leaf to 0 .8 and from 29 per leaf to 9.0 respectively in about 30 days; and when the ratio s of the predaceous mite/the lady beetle/the red mite were 1/0.5/30, the den sity of the prey decreased rapidly from 24 per leaf to 0.2 in 27 days only.