ISHS Acta Horticulturae 695: I International Symposium on Tomato Diseases
CONTROL OF EARLY BLIGHT OF TOMATO WITH GENETIC RESISTANCE AND CONVENTIONAL AND BIOLOGICAL SPRAYS |
| Authors: | T.A. Zitter, J.L. Drennan, M.A. Mutschler, M.J Kim |
| Keywords: | Alternaria tomatophila, early blight, Lycopersicon esculentum, tomato, genetic resistance, fungicides, biological control |
| Abstract:
Most tomato cultivars (Lycopersicon esculentum) are very susceptible to foliar infection with early blight (EB) caused by Alternaria tomatophila. Limited studies have compared the use of conventional and biological fungicides for early blight control, and the contribution of early blight resistance (EBR). For the conventional fungicide trials, the cultivar Supersonic was sprayed weekly with chlorothalonil (Bravo Ultrex), pyraclostrobin (Cabrio) alternated with Bravo Ultrex, the biological agent Bacillus subtilis (Serenade) + copper hydroxide (Kocide), B. pumilus (Sonata) + Cabrio in 2002, and Serenade + Cabrio in 2003. In an adjoining field in 2002, we tested two homozygous EBR tomato lines, a heterozygous EBR hybrid, and a susceptible tomato line. Sonata was applied alone or combined with Cabrio, plus an unsprayed control. In 2003 we evaluated tomato homozygous and heterozygous for EBR, and two susceptible tomato lines using Serenade + Kocide alone or alternated with Cabrio, plus an unsprayed control. Both 2002 trials were inoculated with the dark phenotype of A. tomatophila, while the light phenotype was used in 2003. The 2002 growing season was hot and dry, limiting EB development in both trials. In the fungicide trial, Bravo Ultrex and Serenade + Kocide provided good control, while Sonata + Cabrio gave excellent control. In the germplasm trial, Sonata alone did not provide adequate control for any genotype, while the Cabrio/Sonata treatment provided excellent control for all tomato entries. Early blight was much more severe in 2003 when the light phenotype was used. In the fungicide trial, Serenade + Cabrio provided slightly better control than Bravo Ultrex, but Serenade + Kocide did not provide adequate control. There were significant differences among both the chemicals and genotypes tested. Serenade + Kocide provided good control for both the heterozygous and homozygous EBR lines, while Cabrio alternated with Serenade + Kocide performed well with all genotypes, and was significantly better for the homozygous EBR line. | |
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