A cut stem on this tomato plant indicates that the plant is infected with a bacterial disease. Bacterial canker (Clavibacter michiganensis pv michiganensis) is one of the most destructive tomato diseases in Massachusetts. Initial symptoms first affect the lower leaves causing leaf curling, wilting, chlorosis and shriveling. The pathogen spreads throughout the plant and causes poor growth, wilt and plant death. Stems can split resulting in open breaks or cankers and can break easily. Secondary infections occur from water splash onto foliage, stems and fruit. Spots occur on green fruit and are very characteristic: white to yellow spots, with raised brown centers.
Management: Garden retailers and greenhouse tomato growers are advised to purchase locally grown tomato plants that have been started in the northeast from certified, disease-free seed or treated seed (hot water, hydrochloric acid, calcium hypochlorite etc.). Control bacteria populations that may be present on the leaf surface of transplants in the greenhouse. Note that young transplants may not display symptoms of bacterial diseases. Inspect and remove suspected transplants. Contact your University plant diagnostic laboratory for confirmation. Avoid damaging leaves by watering. Bacteria on the surface of tranplants can be effectively controlled by sprays of copper hydroxide or streptomycin in the greenhouse. Bacteria survive as long as there is any infected crop debris: promptly remove and destroy affected plants and crop debris. Sanitize any tools (clippers, knives) used on the crop with a disinfectant.