Managing diseases of organic tomatoes in greenhouses and high tunnels

Production of tomatoes in greenhouses and high tunnels has increased in popularity significantly in the last decade. Both provide the option of off-season production and expansion of markets over traditional outdoor field systems. While greenhouse tomato culture tends to be very high-tech and capital-intensive, high tunnels expand the growing season in both spring and fall with much lower capital investments. Greenhouse and high tunnel systems pose unique pest management challenges. The “protected culture” of greenhouse and high tunnel production may result in lower incidence of diseases exacerbated by rainfall, such as Septoria leaf spot and bacterial spot and speck. However, diseases that are uncommon in open fields may appear under protected culture. Botrytis blight/gray mold, white mold (timber rot) and leaf mold are among the most important of these diseases. Late blight may also occur under cool, moist conditions, while powdery mildew has occurred in many greenhouses under drier conditions.