Enhancing Natural Pest Resistance in Apple Orchards through Understory Plant Communities and Fruit Chemistry

Commodities

Practices

Apple orchards in the southeastern United States face persistent pressure from insect pests that reduce fruit quality, increase production costs, and drive reliance on chemical inputs. Codling moth (Cydia pomonella) and plum curculio (Conotrachelus nenuphar) are among the most economically damaging pests in apple production, often requiring repeated insecticide applications and raising concerns about resistance evolution and environmental impacts. A more sustainable alternative is to boost natural plant immunity through practices such as cover crops and precision fertilization strategies, but the mechanistic understanding of how these practices influence fruit-level resistance to insect pests remains limited. This project will evaluate whether increasing understory plant communities, in combination with precision nutrient management guided by plant sap analysis, enhances apple fruit chemical defenses and reduces pest damage. Using an established research orchard at Virginia Tech, the study will examine two ground management practices (herbicide and cover crop mixtures) with two nutrient managements (conventional and precision regenerative). Apple fruit will be assessed for pest damage and analyzed for targeted phenolic and terpenoid compounds in both skin and pulp tissues. Laboratory bioassays will quantify resistance to codling moth and plum curculio and link pest responses to fruit chemical composition. By integrating understory communities, nutrient management, fruit chemistry, and pest performance, this research will determine whether ecologically-based practices can strengthen natural plant defenses in apple orchards. Results will inform sustainable orchard management strategies that reduce reliance on chemical inputs while maintaining fruit quality, yield, and economic viability for apple growers in the southern United States.

This project aims to determine whether increasing understory plant communities enhances the natural resistance of apples to pests through changes in fruit chemistry under different nutrient management regimes. We hypothesize that increasing understory plant communities, combined with precision nutrient management, enhances apple fruit chemical defenses, leading to reduced pest damage by codling moth and plum curculio while maintaining yield and fruit quality.

To test this hypothesis, we will pursue the following objectives:

Obj. 1: Quantify the effects of ground management systems (cover crops vs herbicides) and nutrient management systems (conventional vs precision regenerative) on fruit chemical defenses, including phenolics and terpenoids

Obj. 2: Evaluate pest responses to fruit across these management systems by assessing codling moth and plum curculio performance in laboratory bioassays.

Obj. 3: Determine whether variation in fruit chemistry explains pest damage patterns by linking phenolic and terpenoid concentrations to pest performance and damage across treatments.