Within-nest distribution of Mondontomerus spp. (Hymenoptera: Torymidae): Impact on osmia cornifrons (Hymenoptera: Megachilidae) propagation for pollination

Monodontomerus spp. (Hymenoptera: Torymidae) is a parasitic wasp of solitary Megachilidae, such as Osmia spp. (Hymenoptera: Megachilidae). Monodontomerus eggs are laid inside nest cells of the host bee and when the eggs hatch the host bee larvae is consumed by the developing wasps; this makes Monodontomerus a key pest in Osmia propagation for orchard polliantion. To determine spatial pattern of Monodontomerus parasitism within Osmia cornifrons nest bundles, ten bundles of 100 cardboard nest tubes were placed in a blueberry orchard in Independence, WV in May. The nest bundles were then brought into the lab in October, and the number and location of Monodontomerus oviposition holes was recorded for each nest. The spatial distribution of oviposition holes was analyzed using geostatistics in GS+ version 9. The average number of holes per nest was 1.2 ± 1.43. The best fit model for the variogram was exponential (nugget = 0.295; sill = 0.712; range = 10.77). The spatial pattern of the holes showed Monodontomerus preferred nests on the outer perimeter of the nest bundle. The results of this study indicate that when managing Osmia in cardboard tube bundles, Osmia bee nests on the outside of the bundle are highly susceptible to parasitism by Monodontomerus.