Chemical treatments for control of decay in pruning wounds

Wound treatments were evaluated, in the laboratory and the field, for their effect on beech and poplar tissue (phytotoxicity) and on the growth and colonisation pattern of micro-organisms. Three types of treatment were examined: a physical barrier or sealant, a sealant plus fungicide and a fungicide alone. Greatest phytotoxicity was shown by materials normally employed as timber preservatives and the least by sealants. Generally colonisation by fungi and bacteria was little delayed by most treatments with the exceptions of Santar (sealant plus mercuric oxide) and Australian Arborseal (sealant plus captafol). However, colonisation by basidiomycetes was generally delayed by treatment, but its overall intensity was reduced only by Santar and Lac Balsam (sealant). Some treatments had a selective effect on the species of micro-organisms colonising a wound - thus wounds treated with carbendazim derivatives were most likely to be colonised by basidiomycetes and Alternaria spp. Treatment with Santar discouraged most micro-organisms with the exception of Phoma spp. No sealant provided a visually intact cover for longer than 12 months: even wounds with apparently intact cover occasionally had fruit bodies of decay fungi present on them. The chemicals triadimenol, triadimefon, carbendazim and thiophanate methyl were still present in fungicidal amounts in wounds up to at least 157 days. Both Santar and triadimenol prevented the growth of Trametes versicolor from inoculum plugs in wounds of apple trees.