木芙蓉上亚利桑那跳小蜂对扶桑绵粉蚧的寄生研究

Parasitism of the Cotton Mealybug Phenacoccus solenopsis Tinsley by Parasitoid Wasp Aenasius arizonensis (Girault) on Hibiscus mutabilis L.Plants

扶桑绵粉蚧Phenacoccus solenopsis Tinsley是我国重要观赏和药用植物木芙蓉上的主要害虫之一,但迄今对其被优势天敌亚利桑那跳小蜂Aenasius arizonensis (Girault)(班氏跳小蜂A.bambawalei Hayat)的寄生情况了解甚少。为此,自2017年开始,在浙江兰溪西部的一个木芙蓉种植区开展了为期四年的调查,每年6—9月,分批从木芙蓉植株上采集3龄若虫及未产卵雌成虫,于室内观察寄生情况;并于其中两年观察了不同生境中的寄生情况,探讨了寄生季节变化的动态特征及相关影响因素、杂草促进寄生的途径以及增强该粉蚧自然控制的措施。结果表明,在前期(6—7月)寄生率总体上较低,其中两年最高分别仅有38%和32%,另外两年也很少发现被寄生个体,而且该时期寄生率年份间存在明显波动。而在后期(8—9月),寄生率相对较高,且具有从8月上旬开始逐步上升这一显著特点。观察期间,最高寄生率均出现于各年份9月下旬,四年中分别为89%、62%、55%和13%,年份间差异十分明显。生境类型可对寄生水平产生较大影响,与木芙蓉地块内和杂草稀疏的田埂相比,杂草丛生的田埂上和路边区域中粉蚧被寄生率相对较高;另外,在毗邻田块的路边地段,9月上旬的寄生比例一定程度上高于距离木芙蓉地块较远的路边地段。本研究表明,木芙蓉上亚利桑那跳小蜂对扶桑绵粉蚧的控制作用随年份和季节剧烈变化,一些生境诸如杂草较多的地段有利于增强其控害作用。

The cotton mealybug,Phenacoccus solenopsis Tinsley,is one of major insect pests of Hibiscus mutabilis L.,an important horticultural and medical plant in China.However,so far little is known about levels of its parasitism by Aenasius arizonensis(Girault)(=Aenasius bambawalei Hayat)(Hymenoptera,Encyrtidae),which is a dominant natural enemy of this mealybug.Since 2017,we investigated this issue for four years in a H.mutabilis growing region in western Lanxi,Zhejiang province by collecting nymphs and adult females at intervals during June to September from H.mutabilis plants and observing for parasitism rates in the 3rd instar nymphs and un-ovipositional females in the laboratory.Moreover,the parasitism of two years was compared between different habitats.This study was aimed to discover seasonal dynamics of parasitism and responsible factors,possible approaches of weeds in promoting parasitism,and measures to be taken to enhance biological control of the mealybug.During early seasons(June and July),the overall parasitism rate was much low,with the highest being only 38% and 32% respectively in two of the four years while few parasitized individuals occurred in the other two years.Moreover,during this season the parasitism fluctuated evidently between years.During late seasons(August and September),however,the parasitism rate was much higher,increasing since early August.The highest parasitism rates were observed in late September,89%,62%,55% and 13% respectively in the four years,which differed remarkably among years.Habitat could affect parasitism level to a great extent.As compared with the mealybugs collected from H.mutabilis fields and the levees with sparse weeds,those collected from weed-dense levees and roadsides were parasitized at higher rates.In addition,the parasitism rate was higher to certain degrees at the roadsides neighboring to H.mutabilis fields as compared to those far from fields.In conclusion,the natural control of A.arizonensis against P.solenopsis on H.mutabilis varies tremendously with years and seasons,and it can be potentially enhanced in some habitats such as those abundant with weeds.