Carrot virus Y (CarVY) is a newly described potyvirus that causes a foliar and root disease in carrots which seriously diminishes yield and quality. It infects crops in most commercial carrot producing areas of Australia. Infection sometimes reaches very high incidences within individual crops resulting in their being abandoned due to unmarketability of the roots. A range of commonly grown carrot cultivars were all susceptible. CarVY symptoms in carrot foliage are chlorotic mottle, marginal necrosis or reddening and generalised chlorosis of leaves, increased subdivision of leaflets giving a 'feathery' appearance and plant stunting. Roots from plants infected early are stubby showing severe distortion and knobliness, while those from plants infected late are thin with little distortion. The known host range of CarVY is narrow and the key infection sources for spread by aphid vectors to newly sown crops are infected 'volunteer' carTots and adjacent infected carrot crops. Continuous irrigated carrot production in sequential plantings on the same farm all-year-round results in massive infection with the virus, while discontinuous production results in low incidences. Exposure of young carrot plants to peak aphid populations initiates early epidemics. Case histories showing how control measures affected CarVY incidence are described for one farm that deployed them compared with one that did not. An integrated control strategy devised for sustainable management of CarVY in carrot crops is described. Preliminary tests indicate that seed transmission of CarVY may occur at low levels in carrot, so introduction of the virus to isolated sites may be from inadvertent sowings of contaminated carrot seed. (C) 2003 Elsevier B.V. All rights reserved.