Bacterial Canker Present in Ohio Tomato Fields

This article was written by Dr. Francesca Rotondo.

This article has been reposted from the Fruit, Vegetable & Specialty Crop News, to view the original article, click HERE!

Bacterial canker (BC), caused by Clavibacter michiganensis, affects both tomato and pepper plants. The disease is seedborne and can be introduced through infected seed or transplants. It spreads through mechanical transmission during pruning and other field or greenhouse operations. The bacterium thrives with high humidity and warm temperatures, and heavy rainfall further contribute to its spread and secondary infections.
In tomatoes, bacterial canker is more severe because the bacterium invades the vascular system. Early symptoms include stunting and wilting, followed by open cankers on the stem. When stems are split open, a thin, reddish-brown discoloration is visible in the vascular tissue, especially at the base and nodes. Secondary symptoms include browning of leaf edges (“firing”), upward curling of leaflets, and small, tan fruit lesions with a white halo, known as “bird’s-eye” spots. (Figure1)
In peppers, the infection is not systemic. It primarily causes foliar symptoms and affects fruit, leading to yield reductions (Figure 2). Canker-infected pepper fields can also serve as sources of inoculum for nearby tomato fields.

Figure 1. Characteristic symptoms caused by bacterial canker in tomato: wilting (A), vascular discoloration (B) and bird-eye lesion on fruit (C

Figure2. Typical symptoms caused by bacterial canker on pepper leaves (A) and fruits (B)

Managing bacterial canker is challenging once it is present. Prevention and sanitation are crucial for an effective management:
• Start with certified and disease-free seeds and transplants
o sanitize seed using hot-water treatment (ohioline.osu.edu/factsheet/hyg-5818).
• Disinfect all tools and equipment to prevent contamination
• Regularly scout for symptoms, and destroy infected plants
• Rotate crops, avoiding tomatoes in infected fields for 3-4 years
• Ensure fields are free of weeds or volunteer tomato plant
• Reduce stresses with balanced nitrogen, improved soil organic matter, and well-drained soil
• Copper fungicides and streptomycin should be applied before transplanting to the field, and copper fungicides can help slow the disease’s progression during the growing season

In 2019 and 2021, the Vegetable Pathology Laboratory (Dr. Sally Miller and Dr. Francesca Rotondo) conducted trials to assess the natural resistance of different pepper varieties (bell pepper, banana, and jalapeño). In 2019, the percentage of marketable fruits was significantly higher in jalapeño and banana varieties compared to bell pepper (80% vs. 60%) (Table1a). In 2021, chili varieties had the highest percentage of marketable fruits (95%), followed by jalapeño (88%), banana (82%), and bell pepper (75%) (Table 1b).

Table 1: results from the field variety trials conducted in 2019(a) and 2021 (b)

In 2021, the Vegetable Pathology Laboratory also evaluated the efficacy of biorational products against bacterial canker in pepper seedlings in two independent greenhouse trials. Theia, Regalia (giant knotweed extract), and Howler reduced BC severity by 78%, 73%, and 68%, respectively, in the first trial. Similar results were observed in the second trial, with Regalia, Howler, Theia, Vacciplant (laminarin), and Stargus (Bacillus amyloliquefaciens F727) reducing disease severity by up to 80% This research was funded by the Ohio Vegetable & Small Fruit Research & Development Program (OVSFRDP).