Assessing natural enemy and life-stage diversity on alfalfa aphid suppression

Alfalfa is the third most valuable field crop produced in the U.S., valued at over $9.3 billion. Four aphid species, including the spotted alfalfa aphid (Therioaphis maculate Buckton), cowpea aphid (Aphis craccivora C.L. Koch), pea aphid (Acyrthosiphon pisum Harris), and blue alfalfa aphid (Acyrthosiphon kondoi Shinji), are among the most serious pests in alfalfa production, typically managed using insecticides. Broad-spectrum insecticides can harm natural enemy communities, leading to pest outbreaks. Higher species richness of natural enemies is expected to increase aphid suppression. Most research, however, has focused on a single life-stage (i.e., adults) and many enemies in the community have immature life-stages that are predatory, differ in niche space and prey resources, and overlap with adult stages. Therefore, this project aims to investigate the impacts of natural enemy diversity across multiple life-stages on aphid suppression. A cage study will be conducted at the Leyendecker Plant Science Research Center at New Mexico State University in 2024. Using Lumite field cages, we will establish pea aphid populations and introduce combinations of natural enemies, including ladybeetles, Nabis sp., and Geocoris sp., in different life-stages (immature, adult, combination). Destructive sampling will be used to assess pest and enemy populations and alfalfa yield. The effect of natural enemy and life-stage diversity on aphid suppression will be evaluated using ANOVA. We predict that higher natural enemy diversity and including multiple life stages will enhance aphid suppression. Our findings will help growers manage alfalfa pests more effectively, reduce insecticide reliance, lower environmental costs, and mitigate insecticide resistance.