Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2016
Publication Date: 3/16/2016
Citation: Herlihy, M.V., Talamas, E.J., Weber, D.C. 2016. Attack and success of native and exotic parasitoids on eggs of Halyomorpha halys in three Maryland habitats. PLoS One. 11(3):e0150275.
Interpretive Summary: Brown marmorated stink bug (BMSB) is an invasive Asian pest, now widespread and causing damage to vegetable, fruit, and field crops in North America, as well as being a nuisance by overwintering in buildings. To manage this pest problem, we must discover the best methods to suppress populations, including biological, chemical, behavioral, and cultural controls. Some of the most important biological controls for stink bugs are tiny beneficial parasitoid wasps which kill stink bug eggs by laying their own eggs in them, producing wasps instead of bugs. We placed so-called sentinel BMSB eggs in three habitats -- woods, orchard, and soybean field -- to test what egg parasitoids would attack the bug eggs, and whether the wasps could develop and emerge successfully from BMSB eggs. Freezing the sentinel eggs killed the bug embryos and allowed the parasitoids to develop more easily, giving a measure of their maximum potential parasitism. These were compared to live eggs, from which some parasitoids were incapable of developing and emerging. Four species of native North American parasitoid wasps developed and emerged from over 20% of frozen egg masses, but fewer than 3% of fresh (live) egg masses, showing that native parasitoids were virtually incapable of successfully parasitizing live BMSB eggs. To our surprise, we also detected a non-native parasitoid from Asia, which was not previously known in North America. This species did successfully parasitize and emerge from BMSB eggs, as it is known to do in Asia. Parasitoid species, native and non-native, were found to specialize in specific habitats. Our results will help to determine if the current group of native egg parasitoids, along with the newly-discovered Asian wasp, is capable of suppressing BMSB populations in North America, based on habitat specialization, possible future adaptation of native parasitoids to BMSB, and spread of the non-native wasp species. This research will be of interest to researchers, pest managers, and growers of crops damaged by BMSB.
Technical Abstract: Egg parasitoids of the exotic invasive brown marmorated stink bug, Halyomorpha halys (Stål), were investigated using lab-reared fresh (live) and frozen (killed) lab-reared sentinel egg masses deployed for 72h on foliage in three habitats -- woods, orchard, and soybean field -- in Maryland, USA, in summer 2014. Four native hymenopteran species, Telenomus podisi Ashmead (Scelionidae), Trissolcus euschisti (Ashmead) and Tr. brochymenae Ashmead (Scelionidae), and Anastatus reduvii (Howard) (Eupelmidae), developed and emerged from H. halys eggs. One exotic parasitoid, Trissolcus japonicus (Ashmead) emerged, providing the first known occurrence of this species in North America. Native parasitoids emerged from frozen eggs significantly more often than from fresh eggs (89.3% of egg masses and 98.1% of individual eggs), whereas the exotic Tr. japonicus did not show a similar difference, strongly suggesting adaptation to H. halys as a host by Tr. japonicus but not by the native species. Parasitoids were habitat-specific: all three Trissolcus species were significantly more likely to occur in the woods habitat, whereas Te. podisi was found exclusively in the soybean field. Futher investigations are required to elucidate evolving host-parasitoid relationships, habitat specificity, and non-target effects of Tr. japonicus over the expanded range of H. halys in North America.