Tomato production in Ohio protected culture systems is hindered by a soilborne disease complex consisting of corky root rot (Pyrenochaeta lycopersici), black dot root rot (Colletotrichum coccodes), Verticillium wilt (Verticillium dahliae), and root-knot (Meloidogyne hapla and M. incognita). In a survey of 71 high tunnels, C. coccodes was detected in 90% of high tunnels, while P. lycopersici (46%), V. dahliae (48%) and Meloidogyne spp. (45%) were found in nearly half of high tunnels. Anaerobic soil disinfestation (ASD) with wheat bran (20.2 Mg/ha) plus molasses (10.1 Mg/ha) and grafting onto ‘Maxifort’ or ‘Estamino’ rootstocks were evaluated in high tunnels on five farms. In post-ASD bioassays using trial soils, root and taproot rot severity were significantly reduced following ASD, and root-knot galling was also reduced by ASD. Soilborne pathogenic fungi were isolated less frequently from bioassay plants grown in ASD-treated soils than control soils. Similar results were observed in tomato plants grown in high tunnels. Root rot was significantly reduced by ASD in nearly all trials. Corky root rot severity was highest in non-grafted plants grown in non-treated soils, while the lowest levels of corky root rot were observed in Maxifort-grafted plants. Black dot root rot severity was higher or equivalent in grafted plants compared to non-grafted plants. Root-knot severity was lower in plants grown in ASD-treated soils in high tunnels compared to plants grown in control soils, but grafting did not significantly decrease root-knot severity. However, soil treatment did not significantly impact yield, and grafting led to inconsistent impacts on yield.

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Streptomycin is the primary method used to control apple blossom infections caused by Erwinia amylovora in the United States (US). Improper use of streptomycin can contribute to resistance development in E. amylovora and other epiphytic bacteria in the apple tree. Streptomycin resistant (SmR) E. amylovora strains have been reported in several apple production states in the US, however, the prevalence and genetic basis of E. amylovora resistance in Ohio (OH) orchards is reported for the first time in this study. While most strains isolated from OH were sensitive to streptomycin, 7.8% had a resistant phenotype with a minimum inhibitory concentration (MIC) of 500 or 2500 µg/ml. Resistance was conferred by the linked strA-strB genes on the non-conjugative plasmid pEA29. Only one strain (MIC=2500 µg/ml) did not have the linked strA-strB genes or a mutation in codon 43 of rspL. Epiphytic bacteria, including other species of Erwinia and species of Pantoea, with a resistant phenotype were also recovered from apple blossoms. Epiphytic isolates (44%) were resistant up to 500 µg/ml and 56% up to 2500 µg/ml. The genetic basis for resistance of a subset of epiphytic bacteria (n=54) was confirmed to be through the presence of the plasmid transmitted gene pair, strA/strB.

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