Control of the Foliar Disease, Septoria lycopersici, in Organic Tomato Production

Abstract

Disease management in organic tomato production poses one of the greatest challenges for organic producers in humid climates. Both organic and conventional tomato growers have relied on copper (Cu) fungicides to control many diseases, including Septoria lycopersici common in tomato production. Concerns have been raised regarding the use of Cu fungicides, because of their potential to cause plant damage and toxicity to beneficial organisms. The objectives of this research were to: 1) investigate the efficacy of compost tea made from either windrow composted cattle manure (WCCM) or vermicomposted cattle manure (VCM), and 2) compare the efficacy of organic fungicides with conventional fungicides to control S. lycopersici in organic tomatoes. Treatments included 1) a control, 2) a conventional treatment in which fungicide applications of Bravo plus Cu and Quadris plus Cu were alternated, 3) copper fungicide (Champion), 4) Serenade™ Fungicide (Bacillus subtilis), 5) WCCM compost tea, and 6) VCM compost tea. Disease pressure was mostly from the bacteria speck/spot complex. Disease severity was significantly (P < 0.05) reduced and marketable yield was 60% higher with the two Cu treatments (No. 2 and 3), compared to other treatments. A follow-up greenhouse experiment is in progress and will be presented with the field data.