USDA-ARS Red River Valley Agricultural Research Center, Biosciences Research Laboratory, 1605 Albrecht Blvd, Fargo, ND 58102-2765, USA.
J Econ Entomol. 2012 Feb;105(1):14-9. doi: 10.1603/ec11210.
Synchronizing Megachile rotundata (F.) nesting activity with alfalfa bloom is essential for ensuring optimal pollination for alfalfa seed production. This is achieved by timing the initiation of spring bee incubation so that adults will emerge -2 wk before peak bloom. If weather conditions change so as to delay the bloom, bee managers will commonly expose the developing bees to a period of low-temperature incubation to slow their development. We have previously demonstrated survival during low-temperature incubation can be significantly increased by using a fluctuating thermal regime (FTR) where the bees receive a daily pulse at 20 degrees C. A FTR incubation protocol is composed of a number of different components, such as the base and pulse temperatures, and the duration and frequency of the pulse. In this investigation, the effect of the duration of the pulse (5-120 min) and the frequency of a pulse (twice daily to weekly) on the survival of developing M. rotundata was examined. A pulse as short as 5 min at 20 degrees C increased survival of the developing bees as compared with the constant 6 degrees C controls. Increasing the pulse duration induced a further increase in tolerance to 6 degrees C. As with the pulse duration, increasing the pulse frequency from once weekly to twice daily had a significant effect on improving the bees tolerance to low-temperature incubation. This investigation further strengthens the argument that a FTR protocol is superior to using a constant low-temperature exposure for interrupting the spring incubation of M. rotundata.
同步巨型熊蜂（F.）筑巢活动与紫花苜蓿开花期对于确保紫花苜蓿种子生产的最佳授粉至关重要。这可以通过控制春季蜂孵化的开始时间来实现，以使成虫在盛花期前 2 周出现。如果天气条件发生变化导致花期延迟，蜂管理人员通常会使发育中的蜜蜂暴露在低温孵化期，以减缓其发育。我们之前已经证明，通过使用波动热环境（FTR）可以显著提高低温孵化期间的存活率，在这种环境中，蜜蜂每天在 20°C 下接受一次脉冲。FTR 孵化方案由多个不同的组件组成，例如基础和脉冲温度以及脉冲的持续时间和频率。在这项研究中，检查了脉冲持续时间（5-120 分钟）和脉冲频率（每天两次到每周一次）对发育中的巨型熊蜂的存活率的影响。与 6°C 的恒定对照组相比，20°C 下短至 5 分钟的脉冲可提高发育中蜜蜂的存活率。增加脉冲持续时间可进一步提高对 6°C 的耐受性。与脉冲持续时间一样，将脉冲频率从每周一次增加到每天两次对提高蜜蜂对低温孵化的耐受性也有显著影响。这项研究进一步证明了 FTR 方案优于使用恒定的低温暴露来中断巨型熊蜂的春季孵化。
