Tomatoes are prone to damage by many foliar, fruit and root diseases. While producing tomatoes in high tunnels protects them from diseases spread by rainsplash such as bacterial spot and Septoria leaf spot, diseases favored by high humidity, including Passalora leaf mold and Botrytis grey mold, can be exacerbated. Producing tomatoes year after year in high tunnels often results in a slow decline over the years in crop productivity due to a buildup of soilborne tomato pathogens. In Ohio, corky root rot, black dot root rot, Fusarium wilt, Verticillium wilt and root-knot nematode are quite common. Our fact sheet describing these diseases can be found here. Our research has shown high levels of these diseases in Ohio high tunnel tomatoes.
If tomatoes have been produced year after year in the same place, even if there are no obvious aboveground symptoms, a few plants in the high tunnel should be dug up as the season comes to a close and their roots washed off and inspected. Healthy roots are abundant and white with an intact taproot and many smaller feeder roots. Plants with corky root rot, for example, may have rotted tap roots and banded dark or “corky” lesions.
What to do if tomato roots appear diseased?
First, find out which diseases/pathogens are present. The Ohio State University Vegetable Pathology Lab and the USDA-ARS Application Technology Research Unit in Wooster are offering free soil testing this Fall for soilborne tomato pathogens. See the flyer here: Soil_testing_flier_1Sep2022
Secondly, consider management tactics for next season. Anaerobic soil disinfestation (ASD) is a non-chemical soil treatment that reduces the populations of soilborne plant pathogens. It is very suitable for conventional and organic high tunnels but should be done while the soil is fairly warm; in Ohio this means ASD treatment should begin by late September. More information on ASD can be found here (factsheet) and here (step by step video).
Once the pathogens have been identified, growers can also choose disease-resistant rootstocks and produce or purchase grafted seedlings. Information on rootstocks and propagators can be found here (see Resources).