EFFECT OF COMPOST WATER EXTRACTS ON GRAY MOLD (BOTRYTIS-CINEREA)

Water extracts of fermented mature composts prepared from animal sources (cattle manure and chicken-cattle manure) and a plant source (grape marc) were tested in growth chamber experiments for their ability to control leaf grey mould on tomato and pepper plants and grey mould on grape berries. Disease was reduced by 56-100% by extracts after a fermentation that lasted more than 10 days. In some cases, even a shorter fermentation time was sufficient. Addition of nutrients to the fermenting mass did not generally improve disease control. Pasteurization of the extracts nullified their efficacy in part and only in some cases. Two bacterial strains isolated from the extracts controlled grey mould effectively. Dilution of the extracts (25-fold) resulted in retention of their efficacy only when they were prepared from grape marc compost. In an experiment conducted under commercial greenhouse conditions, extract of cattle manure compost reduced tomato leaf grey mould significantly (p < 0.05) compared with the water control, but superior disease suppression was achieved with the fungicide vinclozolin. In another experiment, involving a heavy natural powdery mildew (Leveillula taurica) infestation on tomato leaves, partial control of the disease was obtained by all extracts tested.