The effect of fungicide sprays on the incidence of apple canker (Nectria galligena) in Bramley's Seedling

Abstract

In two trials established between 1983 and 1990, copper oxychloride and prochloraz‐manganese applied at 5 and 50% leaf‐fall were as effective as phenylmercury nitrate, formerly used (but now banned) for the control of leaf‐scar infection by Nectria galligena. However, prochloraz‐manganese has not been developed for use on fruit. Autumn application of carbendazim gave inadequate control and thiophanate‐methyl, bitertanol and fenpropimorph were ineffective. Carbendazim applied as a spring‐summer treatment reduced canker development to a similar level to a spring‐summer dodine scab programme plus autumn copper oxychloride. Summer carbendazim + captafol was an outstandingly effective treatment, but since this trial the use of captafol as a fungicide in the UK has been prohibited. In the absence of an effective autumn treatment, penconazole alone or with captan, and myclobutanil preblossom with myclobutanil alone or with mancozeb post‐blossom tended to be less effictive than the standard programme (dodine pre‐ and dithianon post‐blossom). Carbendazim mixed with an effective scab fungicide such as dithianon therefore remains the recommended treatment in an orchard with a serious canker problem. In orchards where there is a limited risk of canker, a spring‐summer scab fungicide programme should prevent N. galligena infection at this time of year, with copper oxychloride applied at leaf‐fall, particularly after wet weather, to prevent leaf‐scar infection. Copyright © 1993, Wiley Blackwell. All rights reserved