Efficacy of organic disease control products on common foliar diseases of tomato in field and greenhouse trials

Abstract

Organic vegetable production continues to increase, while the knowledge about how to best manage foliar diseases in this system has lagged. Several combinations of organically certified products with different modes of action were evaluated for potential to manage foliar diseases of tomato in two field sites with different climatic conditions over two years, and in a greenhouse setting. Early blight, Septoria leaf spot and bacterial spot foliar diseases were naturally present in the field trials, while greenhouse plants were artificially inoculated with a virulent isolate of Alternaria solani, causal agent of early blight. The copper product Badge X2 (23.82% copper oxychloride and 21.49% copper hydroxide), significantly lowered disease levels in all field and greenhouse trials. The biological control product Prestop (Gliocladium catenulatum J1446), significantly lowered early blight disease levels in all field trials and two out of three greenhouse trials. Alternating Serenade Opti (B. amyloliquefaciens QST 713 (syn. B. subtilis QST713), with Regalia (extract of Reynoutria schalinensis) did not consistently lower disease levels compared to the untreated control in field trials. However, Serenade Opti alone lowered early blight disease levels in two out of three greenhouse trials. Sil-Matrix (potassium silicate 29%), and Regalia, applied alone and in combination were generally ineffective in both field and greenhouse trials. An alternation of Oxidate 2.0 (27.1% hydrogen dioxide and 2.0% peroxyacetic acid), which was used to lower the microbe populations on tomato foliage after which Sustane, an aerobically composted turkey litter, was applied to promote colonization by beneficial bacteria, did not consistently lower disease levels compared to the untreated control in greenhouse and field trials. Results of these trials indicate that the biological product Prestop is an effective alternative to copper for the control of early blight, but not necessarily other common foliar diseases in tomato.