Parthenocarpic cucumbers were grown in polyethylene tunnels under commercial conditions and fertilized with N ndash; P ndash; K 7:3:7. During two winter seasons when nitrate level in the fertilizer was low, the addition of potassium to the fertilizer significantly reduced the incidence of fruit grey mould caused byBotrytis cinereaPers.:Fr. by 27 ndash; 33, whereas adding calcium generally reduced grey mould by 35 ndash; 50. The fungicide treatments, diethofencarb and carbendazim (at 0.25ensp;g∙Lminus;) reduced grey mould by 39 and 50, respectively. In the 2nd year stem infection withB.cinereawas decreased by 50, 50, or 60 by treatment with potassium, fungicide, or calcium, respectively. Only the calcium treatment was significantly different from the basic fertilizer control. Calcium treatments were effective on cucumber crops only under high relative humidity at two out of four sampling dates. The effect of calcium could not be separated from high nitrate level associated with its use in cucumber plantings. Potassium enrichment reduced natural incidence of downy mildew (Pseudoperonospora cubensis). Neither ion reduced incidence of powdery mildew (Sphaerotheca fuliginea)in cucumber crops. Disease reduction and increased yield of an eggplant crop were obtained by the addition of calcium to the fertilizer. Grey mould of pepper was reduced by 50 ndash; 60 by adding calcium, but pepper yield was not increased. A single application of calcium sulphate alone or with calcium dihydrogen phosphate to glasshouse plants resulted in a reduction of grey mould in pepper and eggplant artificially inoculated withB.cinerea.Key words:Botrytis cinerea,Pseudoperonospora cubensis,Sphaerotheca fuliginea, calcium, nitrate, potassiu
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