Buteler Micaela, Peterson Robert K D, Hofland Megan L, Weaver David K
Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, 334 Leon Johnson Hall, MT 59717.
Environ Entomol. 2015 Dec;44(6):1571-80. doi: 10.1093/ee/nvv128. Epub 2015 Aug 14.
This study investigated the dynamics of parasitism, host plant resistance, pathogens, and predation on the demography of wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), developing in susceptible (hollow stem) and resistant (solid stem) wheat hosts. This study is also the first to investigate the prevalence and impact of cannibalism on wheat stem sawfly mortality. Wheat stem sawflies were sampled in two commercial wheat fields over 4 yr from the egg stage through adult emergence, and multiple decrement life tables were constructed and analyzed. Cannibalism, host plant resistance, or unknown factors were the most prevalent factors causing egg mortality. Summer mortality of prediapause larvae ranged from 28 to 84%, mainly due to parasitism by Bracon cephi (Gahan) and Bracon lissogaster Muesebeck, cannibalism, and host plant resistance. Winter mortality ranged from 6 to 54% of the overwintering larvae, mainly due to unknown factors or pathogens. Cannibalism is a major cause of irreplaceable mortality because it is absolute, with only a single survivor in every multiple infested stem. Subsequent to obligate cannibalism, mortality of feeding larvae due to host plant resistance was lower in hollow stem wheat than in solid stem wheat. Mortality from host plant resistance was largely irreplaceable. Irreplaceable mortality due to parasitoids was greater in hollow stem wheat than in solid stem wheat. Host plant resistance due to stem solidness and parasitism in hollow stems cause substantial mortality in populations of actively feeding larvae responsible for all crop losses. Therefore, enhancing these mortality factors is vital to effective integrated pest management of wheat stem sawfly.
本研究调查了在易感（空心茎）和抗性（实心茎）小麦寄主上发育的小麦茎蜂（Cephus cinctus Norton，膜翅目：茎蜂科）的寄生、寄主植物抗性、病原体及捕食作用对其种群动态的影响。本研究也是首次调查同类相食现象对小麦茎蜂死亡率的发生率及影响。在4年时间里，从卵期到成虫羽化，在两块商业化小麦田中对小麦茎蜂进行采样，并构建和分析了多重递减生命表。同类相食、寄主植物抗性或未知因素是导致卵死亡的最常见因素。滞育前幼虫在夏季的死亡率为28%至84%，主要原因是被麦茎茧蜂（Bracon cephi (Gahan)）和光滑茎茧蜂（Bracon lissogaster Muesebeck）寄生、同类相食以及寄主植物抗性。越冬幼虫的冬季死亡率为6%至54%，主要原因是未知因素或病原体。同类相食是不可替代死亡率的主要原因，因为它是绝对的，在每个被多个幼虫侵染的茎中只有一个幸存者。在 obligate 同类相食之后，空心茎小麦中取食幼虫因寄主植物抗性导致的死亡率低于实心茎小麦。寄主植物抗性导致的死亡率在很大程度上是不可替代的。空心茎小麦中由于寄生蜂导致的不可替代死亡率高于实心茎小麦。茎的实心度导致的寄主植物抗性以及空心茎中的寄生现象，在造成所有作物损失的活跃取食幼虫种群中导致了大量死亡。因此，增强这些死亡因素对于小麦茎蜂的有效综合虫害管理至关重要。
