Janice LeBoeuf, OMAFRA Vegetable Crop Specialist, Ridgetown
As tomato transplanting begins, it’s a good time to review the strategy for bacterial disease management.
For the field grower, ensure that your transplants have received the recommended copper spray program in the greenhouse. In the field, start to apply a registered copper fungicide within 7 days after transplanting – apply at least 3 applications at 7-day intervals to keep bacterial disease from gaining a foothold in the crop. This protects new growth and replenishes the copper that is washed off by rain and dews. If weather conditions are ideal for bacterial disease (wet weather), you may want to continue applications until early fruit set.
Growers’ decisions on extending the copper sprays may also depend on the end-use of the tomatoes (how many blemishes can be tolerated) and if the plants are under other stresses that may weaken them and make them more susceptible to disease.
The key to this strategy is early prevention and control of bacteria, before the population has a chance to build. Since we cannot predict the onset or severity of bacterial disease, early prevention and control strategies should be a part of your production system every year. Once bacterial disease symptoms are present, it is too late to start to think about control.
Many research trials across North America have shown that tank-mixing mancozeb with copper enhances bacterial disease control.
To review the greenhouse recommendation for tomato transplant production, a registered fixed copper fungicide should be applied according to label instructions, starting 2 ½ weeks after seeding, then every 5 days for a total of 5 applications. Apply in sufficient water to wet foliage just to runoff, not to drench the plug. This should be applied after the last watering of the day.
Notes: Always read and follow label directions. Most bacterial speck populations in Ontario are resistant to copper fungicides.
For more information on tomato bacterial diseases, see the OMAFRA factsheet Bacterial Diseases of Tomato.