Spring Forward: molecular detection of early season predation in agroecosystems

Agroecosystems undergo disturbance early in the season and host simple food webs that are often comprised of pests, generalist predators, and alternative prey. This is a critical time because predator: pest ratios are highest, in favor of predators, and most likely to affect the trajectory of pest populations, a concept we describe as early season predation. Conservation biological control of these pests utilizes on-farm management schemes to increase predator populations, in part, by providing or enhancing alternative resources. These resources may include beneficial alternative prey that sustains predators prior to pest arrival, but if predator affinity for this alternative prey is strong, pest suppression may be disrupted. Early in the season, when the abundance of pests is low compared to alternative prey, predators do not typically consume prey in direct proportion to their relative abundance, often feeding at disproportionately high rates on “rare” prey items. Therefore, molecular tools, such as gut content analysis, have been used to reveal trophic linkages and decouple the relationship between prey abundance and consumption. Using molecular techniques, numerous studies across different agroecosystems have determined that early season predation occurs regularly and may contribute to pest control and is probably most effective for pests with the potential for exponential population growth, where suppression early in the season may be essential to prevent these outbreaks. Studies incorporating molecular tools and field studies can provide insight for growers to create successful conservation biological control programs utilizing generalist predators in early season predation.