Barker Gary M, Addison Paul J
New Zealand Pastoral Agriculture Research Institute, Ruakura Agricultural Research Centre, Hamilton, New Zealand.
J Econ Entomol. 2006 Apr;99(2):273-87. doi: 10.1603/0022-0493-99.2.273.
The South American curculionid Listronotus bonariensis (Kuschel) is an important pest of pastures in New Zealand. Population census data were gathered for L. bonariensis in northern New Zealand pastures during 1980-1983 in the absence of parasitism and again in 1991-1996 after the introduction and establishment of the braconid parasitoid Microctonus hyperodae Loan as a biological control agent. M. hyperodae achieved high rates of parasitism, with 75-90% of overwintering L. bonariensis parasitized within 3 yr of the parasitoid establishing at a site. Multistratum analysis of variance (ANOVA), with allowance for variation in host plant resource (numbers of Neotyphodium-free grass tillers), indicated reduction in the abundance of L. bonariensis life stages in the early part of life cycle. Although providing evidence for suppression of L. bonariensis, these analyses indicated the regulatory role of M. hyperodae was weak because L. bonariensis populations continued to exhibit marked intergenerational variability in abundance. Analyses of life tables indicated larval + pupal survival contributed most to intergenerational changes in abundance, irrespective of presence or absence of M. hyperodae. However, the density dependence of the stage survivals was modified in the presence of the parasitoid, with loss of density-dependent mortality in overwintering adults and increased density dependence in population natality. Regression analyses indicated dual contribution of parasitism and host plant resource to regulation of population natality and population trend in L. bonariensis. We conclude that M. hyperodae is a useful adjunct to host plant resistance in reducing the economic status of L. bonariensis populations in northern New Zealand pastures.
南美象甲类昆虫巴西豆象（Listronotus bonariensis (Kuschel)）是新西兰牧场的一种重要害虫。1980 - 1983年期间，在新西兰北部牧场未发生寄生现象时收集了巴西豆象的种群普查数据，1991 - 1996年，在引入并建立了茧蜂科寄生蜂新西兰牧草象甲茧蜂（Microctonus hyperodae Loan）作为生物防治剂之后再次进行了普查。新西兰牧草象甲茧蜂实现了很高的寄生率，在寄生蜂在某一地点定殖后的3年内，75% - 90%的越冬巴西豆象被寄生。考虑到寄主植物资源（无内生真菌的草茎数量）变化的多因素方差分析（ANOVA）表明，在生命周期早期，巴西豆象各虫态的数量有所减少。尽管这些分析为新西兰牧草象甲茧蜂对巴西豆象的抑制作用提供了证据，但这些分析表明，新西兰牧草象甲茧蜂的调控作用较弱，因为巴西豆象的种群数量在世代间仍表现出显著的变化。生命表分析表明，无论有无新西兰牧草象甲茧蜂，幼虫 + 蛹的存活率对世代间数量变化的贡献最大。然而，在有寄生蜂存在的情况下，各虫态存活率的密度依赖性发生了改变，越冬成虫的密度依赖性死亡率消失，种群出生率的密度依赖性增加。回归分析表明，寄生和寄主植物资源对巴西豆象种群出生率和种群趋势的调控具有双重作用。我们得出结论，在降低新西兰北部牧场巴西豆象种群的经济危害程度方面，新西兰牧草象甲茧蜂是寄主植物抗性的一种有效辅助手段。
