Fungal disease suppression by inorganic salts: A review

This paper reviews the scientific literature on the topic of fungal disease suppression by applications of inorganic salts as alternatives to synthetic fungicides on a global scale for both protected and field crops. Where data were available, the comparative efficacy of inorganic salts with conventional fungicide products is discussed. In total, published evidence was found for 34 inorganic salts (mainly bicarbonates. phosphates, silicates, chlorides and phosphites) that were able to reduce the severity of 49 fungal diseases (of the foliage, stem, fruit, tuber, root and post-harvest) in 35 plant species (vegetables, cereals, fruit crops, root/tuber crops, ornamentals and native plants). The most studied and best controlled disease with inorganic salts was powdery mildew of cucurbits [Sphaerotheca fuliginea (Schltdl.) Pollacci 1913 or Erysiphe cichoracearum DC. 1805: up to 99% efficacy], wheat [Blumeria graminis (DC.) Speer 1975 (f. sp. tritici)] and grapes [Unarm la necator (Schwein.) Burrill 1892]. The next best evidence for disease control was for wheat septoria blotch (Septoria tritici Berk. & M.A. Curtis 1874), rice blast [Magnaporthe grisea (T.T. Hebert) M.E. Barr 1977], potato late blight [Phytophthora infestans (Mont.) de Bary 1876] and several other Phytophthora spp. The published evidence suggests that these 34 inorganic salts are generally less effective than conventional fungicides and could not fully replace them. However, their integration in a disease management strategy may enable a reduction in the number of conventional fungicide applications required. The potential for the inclusion of inorganic salts in fungal disease management programmes merits further investigation and greater regulatory innovation in the near future. (C) 2010 Elsevier Ltd. All rights reserved.