Integrated management of downy mildew of basil

The downy mildew of basil, which is caused by Peronospora belbahrii, is one of the most devastating basil diseases throughout the world, and management programmes with a limited use of fungicides are necessary to control it. In order to develop efficient integrated disease management programmes, the efficacy of alternative products (calcium oxide, zeolite, orange oil with ascorbic acid, potassium phosphites and bicarbonate), applied in different spray programmes in trials carried out under artificial and natural infestations with the pathogen, has been tested. Various combinations of the treatments were chosen, on the basis of the efficacy of the single products, for further testing in experiments carried out in the presence of natural pathogen infestation and under a reduced crop density. The effect of the tested programmes on downy mildew severity (% of affected leaf area), disease development (AUDPC) and yield (fresh weight of plants) was evaluated. Calcium oxide, K-phosphite and orange oil with ascorbic acid generally provided the most consistent disease control (58%, 40% and 26% efficacy, respectively), when used alone under severe disease pressure, compared to the inoculated control. Spray programmes based on calcium oxide, applied 2 to 4 times, in succession to one application of azoxystrobin, and under a reduced crop density, were the most efficient treatment in the presence of a natural infestation by the pathogen; this IPM programme reduced downy severity as much as 80%, providing the same effect as a conventional chemical programme based on the alternation of azoxystrobin, fluopicolide + propamocarb and mandipropamid.