Garlic as a companion plant for suppressing Myzus persicae infestation in Brassica rapa

Companion planting, the practice of growing different plant species together, can be a sustainable pest management strategy. However, the specific role of garlic as a companion plant for Brassica in aphid suppression, particularly against Myzus persicae (Sulzer) (Hemiptera: Aphididae), is not well understood. This study investigated the potential of planting garlic (Allium sativum L., Asparagales: Amaryllidaceae) with Brassica rapa L. (Brassicales: Brassicaceae) to reduce M. persicae infestations and explores its impact on the biocontrol agent Harmonia axyridis Pallas (Coleoptera: Coccinellidae). We hypothesized that the combination of A. sativum and B. rapa would synergistically reduce aphid infestations compared to Brassica monocultures. To test this, M. persicae performance was evaluated on Brassica plants under three conditions: a single Brassica plant (B), two Brassica plants (BB), and a Brassica plant with garlic (BG). Parameters such as aphid survival, fecundity, developmental time, and population increase were measured. Additionally, Y-olfactometer bioassays assessed the behavioral responses of M. persicae and H. axyridis. The results showed that the BG combination significantly reduced aphid survival, fecundity, and population growth while delaying developmental time compared to B and BB. M. persicae preferred volatiles from B and BB plants, while H. axyridis was more attracted to BG volatiles, indicating garlic's potential to enhance biocontrol agent recruitment. This study highlights the potential of garlic as a companion plant to improve Brassica crop protection against M. persicae and enhance the effectiveness of biocontrol agents.