THE ADVANTAGE OF TBZ PLUS IPRODIONE TREATMENT FOR CONTROL OF GRAY MOLD DECAY OF CELERY CAUSED BY THE HETEROGENIC SPORE POPULATION OF BOTRYTIS-CINEREA IN ISRAEL

A combined TBZ - iprodione treatment was mole effective in inhibiting growth in vitro of Botrytis cinerea isolates obtained from decayed celery than either of the fungicides applied separately. This was exhibited for both TBZ-resistant and TBZ-sensitive isolates. TBZ at 500 mu g ml(-1) plus iprodione at 1000 mu g ml(-1) reduced celery decay beyond the reduction obtained by each fungicide alone. When applied prior to inoculation, the combined treatment prevented decay by the TBZ-sensitive/iprodione-resistant isolates and reduced initial decay by the TBZ-resistant/iprodione-sensitive isolates to 3-10% of the level without treatment. Under natural infection conditions iprodione showed better decay control than TBZ, and at 1500 mu g ml(-1) it reduced initial decay during prolonged storage to 3% of the no-treatment level. Although TBZ (500 mu g ml(-1)) or iprodione (1000 mu g ml(-1)) applied separately reduced decay significantly, the combination of lower concentrations of each fungicide was sufficient to eliminate decay development almost totally. The combined treatment also inhibited decay by Sclerotinia sclerotiorum, which contributed 3% of the total soft rot in stored celery.