Where to oviposit: Influence of host plants on Bagrada hilaris (Hemiptera: Pentatomidae) oviposition site selection

Bagrada bug, Bagrada hilaris (Hemiptera: Pentatomidae), is an invasive insect native to Africa, India, and Asia that was introduced to California in 2008. B. hilaris attacks a wide range of cruciferous hosts, including plants in genus Brassica, such as broccoli, cabbage and mustard, as well as other crucifers such as arugula and radish. Although B. hilaris prefers some host plants over others, each plant is susceptible to feeding damage that may significantly affect overall plant health and decrease market value of harvested crops. The ovipositional behavior of B. hilaris is unusual for Pentatomidae, as eggs are often deposited into soil. It is not clear what factors influence oviposition site selection and if host feeding preference affects oviposition behavior. We conducted a series of choice tests to determine the oviposition site preference of B. hilaris when provided with an array of host plants. Ten pairs of adult B. hilaris were added to choice arenas containing potted turnip, alyssum, cauliflower, broccoli, arugula and radish, as well as corn and a pot containing only soil. Over the course of 88 hours (approximately 3.5 days), we documented host selection by observing the number of individuals on each plant and/or soil surface at 2 hour intervals. At the conclusion of the trials, eggs were collected from the soil surrounding each host plant, as well as from the host plant itself. We found that B. hilaris preferred feeding on radish and turnip compared to all other hosts. Although corn is not considered a preferred host plant, we found that B. hilaris is able to feed upon corn. B. hilaris deposited nearly all eggs in the soil rather than on plant tissues, and oviposition site preference was primarily driven by host plant preference. Over the course of our experiment, B. hilaris deposited the most eggs in the soil of the turnip pot, followed by the blank pot containing only soil. Our observations indicate that feeding preference is important for oviposition site selection, although factors other than host preference may also play a role. Further research is needed to determine if these findings may be translated into field management practices.