Alfalfa Mosaic Virus (AMV) on Pepper

Pepper Diseases<strong>Alfalfa</strong> <strong>Mosaic</strong> <strong>Virus</strong>Aphid-Transmitted Bacilliform <strong>Virus</strong>Found worldwideSymptomsThe foliage has a distinct bright yellow to white mosaicthat sometimes causes large areas of interveinal leaftissue to be bleached in appearance. Chlorotic linepatterns and veinal necrosis also may occur. Generally,the leaves are not distorted in shape. If infected whenyoung, the plants may be stunted and their fruit will bemisshapen.World Vegetable CenterConditions for Disease Development<strong>Alfalfa</strong> mosaic virus (<strong>AMV</strong>) is found most commonly inpepper crops that have been planted near alfalfa, cloveror other legumes. It is generally considered to be aminor threat to pepper production.Transmission by seed is the primary means ofestablishment of the virus while aphid transmission ismore important for the subsequent spread in fieldplantings. <strong>AMV</strong> is transmitted by many species ofaphids including the green peach aphid, Myzuspersicae. The aphid can acquire the virus by feeding onan infected plant for less than a minute and can transmitHow to Identify <strong>Alfalfa</strong> <strong>Mosaic</strong> <strong>Virus</strong>Bright yellow to white mosaic patterns on interveinal regions of leaves;sometimes large areas may be affectedBleaching of leavesWritten by Ray Cerkauskas, Visiting Scientist from Agriculture and Agri-Food Canada. Edited by Tom Kalb. Photos by J.M. Poulos, V.Stravato, J.C. Waterson and R.I. Muhyi. Published by AVRDC – The World Vegetable Center; P.O. Box 42, Shanhua; Taiwan 741; ROCtel: (886-6) 583-7801; fax: (886-6) 583-0009; email: avrdcbox@avrdc.org; www: www.avrdc.org

it as quickly, but the aphid actually retains the virus foronly a short period of time. The virus is also readilytransmitted mechanically and by grafting.ControlPepper varieties resistant to <strong>AMV</strong> are not available.Various control measures are required because<strong>AMV</strong> is transmitted by seed, aphids, and mechanically.Control measures must take into account the disease’swide host range (alfalfa, pepper, tomato, tobacco, potato,clover, many cucurbits and beans, and several othercrops and weeds) and numerous aphid vectors.Use virus-free pepper seed. Check transplants forany symptom development and discard those withsymptoms. One or two transplants on either side ofthe affected plants should also be discarded. Avoidtouching or handling healthy plants after handling plantssuspected of virus infection. Wash hands with soapafterwards or use disposable gloves when handlinginfected plants.<strong>AMV</strong>-infected vegetable seedlings are potentialprimary sources of the virus. Cover seedlings with meshsize of 32 or higher to prevent aphids. Do not clip ordamage young seedlings since this increases thepossibility of mechanical transmission of the virus fromcontaminated tools or hands.Aphid control may be difficult because the virus istransmitted very rapidly by these insects. Use fastactinginsecticide sprays since aphids may move toother nearby unsprayed plants when disturbed.Disinfect tools, stakes, and equipment before movingfrom diseased areas to healthy areas. Work in diseasedareas last, after working in unaffected parts of a field.Other less effective measures include: plantingbarrier crops that are not susceptible to <strong>AMV</strong> such ascorn, applying sticky traps, or covering the ground withan aphid deterrent material like aluminum foil strips.Another control strategy is to grow trap crops nearbythat attract aphids and then spray these plants with acontact insecticide to destroy the aphid populations.Also, spray the pepper crop with mineral oil to delayvirus spread in the field by interfering with aphidtransmission of the virus.For more information on the production ofpepper and other vegetables, go to.AVRDC Publication 04-5902004