Spirotetramat for controlling Hemadas nubilipennis within a blueberry integrated pest and pollinator management program

The blueberry stem gall wasp, Hemadas nubilipennis, is a native pteromalid distributed across eastern North America that creates galls on infested young shoots of blueberry plants. In recent years, populations of this native sporadic pest have increased dramatically in fields of susceptible cultivars. In response, some infested fields have been removed and replanted with resistant cultivars, but this is a very expensive approach to reducing infestation. To provide an alternative, we have evaluated potential insecticide options in replicated small plot trials and at commercial blueberry farms. Broad spectrum pyrethroids and methomyl have shown efficacy in both contexts, but their use is restricted due to toxicity to bees during bloom, when H. nubilipennis is active. Neonicotinoids applied after bloom were found to be ineffective, whereas the tetramic acid insecticide spirotetramat applied as a foliar application after bloom was found to significantly reduce the number of galls per bush and to also prevent wasp development within the galls. Here we report on replicated and large scale demonstration tests of this treatment for control of H. nubilipennis as an approach to prevent the recent economic impacts and reduce the need for replanting blueberry fields.