Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT.
Western Triangle Agricultural Research Center, Conrad, MT.
J Econ Entomol. 2020 Aug 13;113(4):1982-1989. doi: 10.1093/jee/toaa097.
Host plant traits strongly affect survivorship of insect herbivores, and host suitability is especially important for the wheat stem sawfly, Cephus cinctus Norton, which spends its entire egg, larval, and pupal periods in a single stem. Measuring larval survival inside stems from egg hatch through diapause-mediated dormancy is a potential measure of population size for the next year but is also useful in assessing effects of growing season precipitation and temperature. Larval growth is synchronized with host plant growth, and the larva cannot switch hosts. Thus, incorporating plant physiological time, as growing degree days (GDD), may yield a better prediction of larval survival. Therefore, we assessed wheat stem sawfly survival from early larval growth to the beginning of autumnal diapause in barley cultivars selected from across feed, forage, and two- or six-row malt groups. Field experiments were conducted in Gallatin and Chouteau counties, Montana, in 2016 and 2017. We used Kaplan-Meier estimation to assess larval survival among cultivars. We found that the survival of pre-diapause larvae was greatest in 'Hockett' (36.5%) and lowest in 'Celebration' (15.4%). Precipitation and temperature during the growing season affected temporal patterns for larval survival across study sites. Adjusting survivorship curves using site-specific GDD accumulation allowed cultivar-specific survivorship to be estimated more precisely for each site, despite differing environmental influences. Our findings suggest that measuring wheat stem sawfly survival across barley cultivars and standardizing by site-specific GDDs may provide better recommendations on barley cultivars that impede wheat stem sawfly population growth and reduce economic losses.
寄主植物的特性强烈影响着昆虫食草动物的生存能力，而寄主的适宜性对小麦茎蜂（Cephus cinctus Norton）尤为重要，因为它的卵、幼虫和蛹期都在一个单一的茎中度过。测量从卵孵化到休眠诱导休眠期间幼虫在茎内的存活率，是预测来年种群数量的一种潜在方法，同时也有助于评估生长季节降水和温度的影响。幼虫的生长与寄主植物的生长同步，幼虫不能更换寄主。因此，将植物生理时间（生长度日，GDD）纳入其中，可能会更好地预测幼虫的存活率。因此，我们评估了从小麦茎蜂幼虫早期生长到秋眠开始的存活率，研究对象是从饲料、草料和二棱或六棱麦芽组中选择的大麦品种。2016 年和 2017 年在蒙大拿州的加拉廷县和乔特奥县进行了田间试验。我们使用 Kaplan-Meier 估计来评估品种间幼虫的存活率。我们发现，预休眠幼虫在“霍基特”（36.5%）中的存活率最高，在“庆典”（15.4%）中的存活率最低。生长季节的降水和温度影响了研究地点幼虫存活率的时间模式。尽管环境影响不同，但使用特定地点的 GDD 积累来调整存活率曲线，可以更精确地估计每个地点的特定品种的存活率。我们的研究结果表明，测量小麦茎蜂在大麦品种间的存活率，并通过特定地点的 GDD 进行标准化，可以更好地推荐那些阻碍小麦茎蜂种群增长和减少经济损失的大麦品种。
