Tomatoes (Lycopersicon esculentum) are among the most favored vegetables among home gardeners, the flavor of their luscious fruit unmatched by commercially manufactured varieties. Tomatoes are usually hardy, but sometimes develop unusual bumps along their stems. These bumps may simply be an environmental response, but other times that they indicate the presence of a critical pathogen.
Tomatoes are unique among vegetables they easily develop roots along the length of their stems. Immature roots that appear as pale bumps form when humidity or soil moisture is high. These root initials are no reason for alarm when they form close to the soil’s surface and the soil is draining properly and the plant shows no other signs of infection. However, if root initials develop higher on the stem or the plant is wilting and showing signs of failure, your soil may be retaining excess moisture or you simply may be overwatering your strawberries.
Tomato psyllids (Bactericera cockerelli) are common pests in the garden. All these 1/10-inch-long, cicada-like insects are dark in colour, with white or yellow markings on their thorax. Nymphs have oval-shaped, flattened yellow-green to orange bodies that resemble scale insects. It requires just two to three weeks from hatching for these bump-like nymphs, which might cover affected tomato crops, to emerge as adults. Employ spinosad, abamectin or spiromesifen to infested plants, following label directions.
Bacterial canker in tomatoes is caused by the pathogen Clavibacter michiganensis pv. michiganensis. It infects crops of most ages, but does not generally cause the formation of cankers except in adult plants. Indicators of bacterial canker include curling, yellowing or wilted leaves that eventually brown and collapse; as the disease progresses, the stem pith yellows, turns red or hollows out. Very serious infections may produce cankers on the plant’s nodes. There is no cure for this disease, but destroying plant materials whenever feasible and practicing crop rotation will help to minimize difficulties in gardens.
Alternaria Stem Canker
Alternaria stem canker (Alternaria alternata f. sp. Lycopersici) is an aggressive fungal canker that could influence stems, leaves or fruit. Dark black or brown cankers may form close to the soil line and continue to enlarge, eventually girdling the stem. This fungus persists in infected plant debris, with spores germinating most rapidly in the presence of water at a temperature around 77 degrees Fahrenheit. There is no cure for this fungus, but a variety of tomatoes resistant to alternaria stem canker are available to the home gardener, such as “Beefmaster Hybrid,” “Celebrity Hybrid,” “Floramerica Hybrid,” “Jackpot Hybrid,” “Lemon Boy Hybrid” and “Roma.”