Reducing the risk of onion bacterial diseases: A review of cultural management strategies

Abstract

AbstractOnion (Allium cepa L.) bacterial diseases can cause catastrophic crop losses. Chemical and biological control products are not curative and have mixed or limited efficacy at preventing onion bacterial diseases. Cultural management strategies, such as appropriate irrigation and nitrogen (N) management practices, can reduce the risk for bacterial infection and disease progression. This review synthesizes available literature on cultural management strategies to mitigate onion bacterial diseases and identifies knowledge gaps, promising strategies, and limitations. This synthesis revealed that high N fertilizer application rates, the use of overhead irrigation, and late‐season irrigation or rainfall, especially during field curing, can increase bacterial disease pressure. These factors contribute to conducive conditions for bacteria to colonize the foliage and neck of onion plants. Other in‐season strategies, such as reducing the total amount of irrigation or adjusting application rates of nutrients other than N, have not limited losses to bacterial bulb rots while maintaining desired yields. At the end of the growing season, appropriate timing of lifting bulbs (undercutting to sever the roots) and other practices that speed field curing can reduce the risk of bacterial bulb rots. However, it is less clear if topping (removing foliage) before or after curing influences bacterial bulb rots. Conflicting results reported for some cultural management strategies indicate that local conditions, such as climate and soil types, must be considered for optimizing practices to manage onion bacterial diseases. Advancing our scientific understanding and grower awareness of strategies that reduce onion bacterial diseases is a cost‐effective opportunity to avoid losses.