Foliar applications of mono-potassium phosphate fertilizer inhibit powdery mildew development in nectarine trees

Foliar applications of 1% solution of mono-potassium phosphae (MKP = KH2P04) fertilizer plus Triton X-100 (0.025%), sterol inhibiting (SI) fungicides, and an alternating treatment of phosphate fertilizer and SI fungicides inhibited development of the powdery mildew fungus Sphaerotheca pannosa on fruits and leaves of nectarine trees in 3 consecutive years. The effectiveness of the alternating treatments with an appropriate systemic fungicide and 1% solution of MKP was similar to that of the commercial treatment with the systemic fungicides alone. However, application of the systemic fungicides only, omitting the phosphate treatment when they were scheduled, was significantly less effective than either the phosphate or the alternation treatments. These results indicate that the use of phosphate fertilizer has a significant role in disease control, enabling up to 50% reduction with number of fungicide treatments required for powdery mildew control. These results were confirmed in a large-scale demonstration ...