Comparison of paint and gel formulations for the treatment of Nectria cankers on apple trees

Abstract

SUMMARYA gel formulation containing carbendazim and triadimefon completely eradicated infection from scraped or unscraped cankers and none became re‐infected. Paint formulations containing mercuric oxide or octhilinone completely eradicated infection from scraped cankers but 30–50% of unscraped cankers receiving these treatments became re‐infected. Scraping alone encouraged callus tissue formation but did not greatly reduce infection.Fungicide moved from gels into the wood beneath cankers and persisted there for up to 6 months; movement of fungicide from mercuric oxide or octhilinone paints was minimal.Carbendazim was more effective than thiophanate‐methyl and xanthan gum than sodium alginate or alginate ester as fungicide and gel component respectively. Rainfall shortly after treatment probably aided movement of fungicide from gels into the wood but salt formation, by incorporation of acid, did little to improve fungicide performance.Unequivocal assessment of efficacy of canker treatment requires data on canker area changes, movement and persistence of active ingredient in the wood and extent of re‐infection after 12 months.