THE EFFECT OF FUNGICIDE SPRAYS ON THE INCIDENCE OF APPLE CANKER (NECTRIA-GALLIGENA) IN BRAMLEY SEEDLING

In two trials established between 1983 and 1990, copper oxychloride an d prochloraz-manganese applied at 5 and 50% leaf-fall were as effectiv e as phenylmercury nitrate, formerly used (but now banned) for the con trol 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, biterta nol and fenpropimorph were ineffective. Carbendazim applied as a sprin g-summer treatment reduced canker development to a similar level to a spring-summer dodine scab programme plus autumn copper oxychloride. Su mmer carbendazim+captafol was an outstandingly effective treatment, bu t since this trial the use of captafol as a fungicide in the UK has be en prohibited. In the absence of an effective autumn treatment, pencon azole alone or with captan, and myclobutanil preblossom with myclobuta nil alone or with mancozeb post-blossom tended to be less effictive th an the standard programme (dodine pre- and dithianon post-blossom). Ca rbendazim mixed with an effective scab fungicide such as dithianon the refore 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 in fection at this time of year, with copper oxychloride applied at leaf- fall, particularly after wet weather, to prevent leaf-scar infection.