Entomology
Permanent URI for this communityhttp://hdl.handle.net/1903/11813
Browse
2 results
Search Results
Item UNDERSTANDING NON-TARGET INSECTICIDE IMPACTS AND OPPORTUNITIES FOR BIOLOGICAL CONTROL IN FIELD CORN(2024) Cramer, Maria; Hamby, Kelly; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Natural enemies can be important regulators of pest populations, replacing chemical pesticides, or where compatible complementing them. To effectively incorporate these biological control services into crop production, we need to understand how pesticides and other management practices impact natural enemies, pests, and their interactions with one another. Using Mid-Atlantic field corn production systems, I evaluated at-planting insecticides and transgenic Bt corn hybrids as tools for insect pest control. In addition, I quantified their impact on predation and on carabid beetle communities. Carabid beetles may be important predators of pest slugs; therefore, I also examined carabid-slug interactions. Finally, I investigated whether a novel pest-management technique (RNAi) could travel up the food chain through pests to predators. At-planting insecticides provided limited pest-management benefits in a three-year field study across Maryland, suggesting that their use could be scaled back to reduce environmental and economic costs. Field and lab experiments revealed carabid beetles are diverse and abundant in corn fields, and a slug predatory carabid species may exert non-consumptive effects on a pest slug. Finally, I determined that a predatory lady beetle species is likely less susceptible to RNAi oral exposure in the adult stage. However, RNAi may still pose risks to predators via trophic exposure. My work supports the adoption of current and future corn pest management practices that protect natural enemies, enhancing biological control ecosystem services and their associated environmental benefits.Item Consequences of omnivory and alternative food resources on the strength of trophic cascades(2007-07-10) Frank, Steven David; Shrewsbury, Paula M; Denno, Robert F; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Omnivorous predators that feed on prey and plant resources are recognized as an important component of food webs but their impact on herbivore populations and trophic dynamics is unpredictable. Feeding on food items from multiple trophic levels increases the reticulate nature of food webs and the labile role of omnivores in promoting trophic cascades. Using carabid beetles in a corn agroecosystem, this research explored the interactive effects of predator guild (omnivore or carnivore) and the trophic origin of alternative food resources (seeds or fly pupae) on the control of herbivores (black cutworms) and plant survival. I demonstrated that the trophic guild and feeding performance of carabids can be predicted from their mandibular morphology. Carnivorous carabids, using mandibles with sharp points and a long shearing edge, kill and consume caterpillars more efficiently than omnivores that have mandibles with wide molar areas adapted for consuming prey and seeds. Omnivore preference for seeds and pupae further reduced their consumption of cutworms, which resulted in increased plant damage, ultimately dampening trophic cascades. In open field plots the abundance of omnivorous carabids and ants increased in response to seed but not pupae whereas neither subsidy affected the abundance of carnivorous predators. Pupae subsidies reduced predation of cutworms by carnivores and omnivores, consequently reducing seedling survival. However, in seed subsidized plots omnivorous predators switched from seeds to higher quality cutworm prey. Thus, predation of cutworms increased with cascading positive effects for seedlings. This research demonstrated that omnivorous carabids interacted more strongly with alternative food resources, particularly seeds, than carnivores. In addition, this difference can be linked to morphological differences that reduced omnivore efficiency as predators suggesting omnivores may be less effective agents of biological control. However, increased tenure time and aggregation to plant resources by omnivores helped restore trophic cascades, and should enhance biological control. Understanding the predacious behavior of omnivores in resource diverse environments is essential to predicting their role in trophic dynamics. I provide evidence that the trophic origin of alternative food drives the strength of this interaction and the extent to which omnivores promote trophic cascades.