Alfalfa mosaic virus in chile peppers: status, management prospects, and research needs

Abstract Alfalfa mosaic virus (Martellivirales: Bromoviridae) is transmitted by several aphid (Hemiptera: Aphididae) species and is known to infect over 600 different plant species worldwide. In 2019, Alfalfa mosaic virus was documented in chile peppers, Capsicum spp. L. (Solanales: Solanaceae), in Colorado for the first time and has caused major yield losses since. The disease has recently also caused severe losses to chile pepper production in California. Symptoms of Alfalfa mosaic virus in chile peppers include severe vein and leaf deformation, leaf curling, and mosaic chlorosis and necrosis of leaves. Infected plants may also exhibit deformities and discoloration of fruit, reducing both yield quality and quantity. Aphids that transmit Alfalfa mosaic virus do so in a nonpersistent manner, which means that the virus is limited to the aphid mouthparts and can be acquired and transmitted within seconds to minutes. Aphids that transmit the virus in Colorado chile peppers do not colonize or habitually feed on the crop but instead infect peppers by inserting their mouthparts into plant tissue while testing plants for host suitability. The nature of the virus and its aphid vectors in chile peppers makes effective management of Alfalfa mosaic virus difficult for Colorado farmers. Here, we summarize pepper production in the United States, Alfalfa mosaic virus distribution and its impact, and the mechanism of Alfalfa mosaic virus transmission. Lastly, we review current management strategies for Alfalfa mosaic virus, discuss potential risks of infection, and identify future research needs for integrated pest management program to suppress this disease in peppers.