飞虱虫疠霉和新蚜虫疠霉对桃蚜的毒力比较

通过飞虱虫疠霉（Ｐａｎｄｏｒａｄｅｌｐｈａｃｉｓ）和新蚜虫疠霉（Ｐ，ｎｅｏａｐｈｉｄｉｓ）对桃蚜（Ｍｙｚｓ　ｐｅｒｓｉｃａｅ）毒 力的生物测定，证实了两种近缘虫疠霉对三日龄若蚜的毒力。两种虫疠霉各包括８个剂量处理，每剂量 接种８８～２１６头若蚜，接种后逐日观察感病死亡数并确诊死因，所获时间－剂量－死亡率数据经模型拟合 分析，结果表明两种虫疠霉具有相似的剂量效应，但飞虱虫疠霉的杀蚜速率比新蚜虫疠霉快。接种后３ ～７ｄ飞虱虫疠霉的ＬＤ５０值分别为１２． ８１，２． ９０，１． ７９，１． ２７，０． ９０个孢子／ｍｍ２，新蚜虫疠霉的ＬＤ５０值分 别为１６． ９６，１． ３０，０． １８，０． ０７，０． ０４个孢子／ｍｍ２．两种虫疠霉的ＬＴ５０值在＞３个孢子／ｍｍ２的剂量下相 似（３．０～３．５ｄ），但低剂量下差异较大。这些毒力指标表明，飞虱虫疠霉是可以与新蚜虫疠霉匹敌的杀 蚜真菌。

Comparison of the virulence of Pandora delphacis and P. neoaphidis (Entomophthorales) to the green peach aphid Myzus persicae.

The two fungal species, Pandora delphacis and P. neoaphidis, were bioassayed for their viru- lence toward the green peach aphid , Myzus persicae For inoculation , batchers of 3-day-old nymphs on detached cabbage leaves (88~216 nymphs per batch) were exposed to spore shower , resulting 8 dosages of each pathogen. The nymphs were examined daily for mortality after inoculation. The resulting data were fitted to a time-dose-mortality model , yielding the parameters for time and dose effests of the two fungal species. Pandora delphacis killed the aphid pest more rapidly than P. neoaphidis though both had similar slopes for dose effect. The estimates of LD50 on days 3-7 after inoculation were 12. 81 , 2. 90, 1.79 , 1.27 and 0. 90 spores/mm2 for P. delphacis, and 16. 96, 1. 30, 0. 18, 0. 07 and 0. 04 spores/mm2 for P. neoaphidis , respectively. The estimates of LT50 for the two pathogens were similar at the dosages of more than 3 spores /mm2 but differed at the lower dosages. The virulence indices indicate that P. delphacis is a promising microbial agent for aphid control competitive with P. neoaphidis.