Local and systemic control of powdery mildew (Leveillula taurica) on pepper plants by foliar spray of mono-potassium phosphate

A foliar spray of 1% (w/v) solution of the fertilizer mono-potassium phosph ate (MKP) (KH2PO4) on the upper surfaces of lower leaves of greenhouse-grow n peppers induced local and systemic control against Leveillula taurica, as compared with control plants. This protection was expressed by a reduction in the leaf area covered with sporulating colonies and in conidial product ion on leaf tissue, 24 or 48 h post-treatment, when MKP was applied on lowe r leaves of plants that had been exposed to the source of inoculum. Foliar application of MKP, initiated before or after exposure to heavily diseased plants as the source of inoculum, was effective in controlling powdery mild ew. Application of MKP efficiently suppressed powdery mildew as expressed b y inhibition of the development of new sporulating colonies, as well as the conidial production of the fungus on infected tissue. Microscopic examinat ion indicated destruction of both hyphae and conidial structures on MKP-tre ated leaves. The efficacy of MKP in controlling powdery mildew on greenhous e-grown plants was compared with a sterol-inhibiting systemic fungicide. Bo th treatments significantly inhibited powdery mildew as compared with non-t reated control plants, although the fungicide-based treatment seemed to be slightly more effective (not significant) in controlling the disease. Phosp hate solutions were not phytotoxic to plant tissue and did not affect the y ield, as compared with the fungicide treatment. However, a lower yield was recorded for the non-treated control plots because of mildew infection on l eaves. These data indicate that MKP spray may be applied as an alternative practice for the control of powdery mildew in peppers. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.