Impact of Reduced Fungicide and Tillage on Foliar Blight, Fruit Rot, and Yield of Processing Tomatoes. Frank J. Louws, Department of Botany and Plant Pathology; Michigan State University, East Lansing 48824. Mary K. Hausbeck, Department of Botany and Plant Pathology, John F. Kelly, Department of Horticulture, and Christine Taylor Stephens, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 80:1251-1256. Accepted for publication 26 July 1996. Copy right 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1251.

The effect of reduced tillage, soil-surface crop residue maintenance, and reduced fungicide input on processing tomato yield and disease incidence was studied in 1990 to 1992. Fall-seeded rye was desiccated in strips in early spring; the remainder, after 1.2 m of growth. Strips were zone tilled (ZT) 35 cm deep with no soil inversion. The ZT system permitted desiccated inter-row rye residue to persist throughout the summer, providing approximately 90% cover of the soil surface. Tomatoes were transplanted into the prepared strips. The ZT system did not affect marketable yield or percent fruit with mold (1991 to 1992); but it decreased (1990), increased (1991), and did not affect (1992) defoliation caused by early blight (EB) compared to a conventional tillage production system using a moldboard plow, disk, or both. The fungicide, Bravo 720 (chlorothalonil), was applied as follows: none, weekly, or a full or reduced rate at intervals according to the disease forecasting model, TOM-CAST, Fungicide treatment did not enhance marketable yield compared to that of the unsprayed treatment. TOM-CAST-based treatments did not consistently provide control of defoliation compared to that in plots sprayed weekly. However, compared to weekly sprays, select forecast-generated spray schedules required 45 to 80% fewer applications to limit fruit mold incidence caused by Alternaria solani (EB), Colletotrichum coccodes (anthracnose), and Rhizoctonia solani (soil rot). Conservation tillage practices, soil-surface residue maintenance, and reduced fungicide input were integrated without compromising yield and management of disease, affording advantages of sustained farmland productivity.

Keyword(s): cover crop, disease forecaster, integrated pest management, sustainable agriculture, zone tillage