Essential concepts for managing Xanthomonas in begonia — Part 2
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EmailCultural practices and chemical treatment of Xanthomonas in begonia.
In Part 1 of this series, we presented an overview of the Xanthomonas bacterial group, typical pathways of bacterial infection and how to recognize the symptoms of Xanthomonas in begonias. In Part 2, we will cover the cultural practices that reduce disease pressure and chemical treatments to prevent the spread of the pathogen.
Tools to limit Xanthomonas are limited; the primary focus should be on prevention. In some cases, plants may not display symptoms immediately after the initial infection, allowing the disease to go undetected.
Once Xanthomonas is detected in the greenhouse, management efforts must include excellent sanitation, cultural practices and likely chemical applications to slow further disease spread.
Cultural disease management
Scouting and rogueing
- Scout begonias at least once per week for symptoms of bacterial leaf spots.
- While wearing disposable gloves, place plants with symptoms in a garbage bag and remove them from the greenhouse.
- Avoid handling wet plant material.
Moisture management
- Minimize the time leaves are wet.
- Avoid watering late in the day or at night to prevent leaves from being wet for a long time.
- When possible, avoid overhead irrigation and apply water directly to the growing media (e.g., drip tape).
- Reduce humidity and ventilate the greenhouse as needed.
Isolation and prevention
- Separate plants based on cultivar and ship date Keep records of the locations of each cultivar in the greenhouse.
- Limit moving plants once they’ve been placed in the greenhouse.
Sanitation
- Wash hands frequently or use disposable gloves when handling plants.
- Disinfect tools between cultivars.
- Remove any plant debris, Xanthomonas can survive on dead leaves.
- Use disinfectant products to sanitize areas where infected plants had been growing (floors, benches, walls, etc.).
- Consider replacing the weed mat after a Xanthomonas outbreak.
Chemical disease management
There are products available that can help protect healthy plants from infection, many of which are included in the Greenhouse Disease Management Guide by Mary Hausbeck, PhD, a plant pathologist at Michigan State University. Products listed for bacterial disease control contain copper as an active ingredient. Bacteria may be resistant to copper, so it is important to integrate cultural strategies with copper application.
Copper-based products vary in their formulations and percentage of copper. When choosing a product, take note of the restricted-entry interval (REI), personal protective equipment (PPE) requirements, and crop tolerance information included on the product label. Test any unfamiliar products on a small number of plants to assess the visible residue that may affect crop marketability.
Part 3 will present some scenarios in a question-and-answer format and help you rogue through the crop to minimize losses.
Contact a member of the Michigan State University Extension floriculture team for additional information and technical assistance.
Reference to commercial products or trade names does not imply endorsement by Michigan State University Extension or bias against those not mentioned.
