Controlling Xanthamonas on Hiemalis Begonias
The thought of Xanthamonas strikes fear into the heart of every Begonia propagator but to growers just growing finished crops the problem can be controlled if you have good cultural practices. It is only spread by physical contact and splashing water from infected plants that are exhibiting symptoms. If you are propagating there is much more to be concerned about because it can be spread while taking cuttings even on infected plants that aren’t showing symptoms and the propagation area with mist and overhead watering greatly increases the chance of spreading the bacteria. Zerotol injected into mist water will control spread in propagation beds but will not cure infected cuttings.
A plant that is infected with Xanthamonas can not be cured of the disease but you can prevent the spread to other plants if you are aware of the problem and act responsibly. As soon as symptoms are noticed on a plant it should be thrown out so that it can not contaminate other plants. You want to be careful not to touch the infected plant parts and wash your hands after dumping the plant (do not put it in your compost pile). You may want to throw away the plants next to the infected plant too if there was plant to plant contact or if there was splashing water between the plants. A weekly spray of Kocide (a copper fungicide) will reduce the chance of spread from plant to plant by water or contact. Phyton 27 also works well for one application but repeated sprays may cause phytotoxicity. The copper sprays are no longer beneficial once the plants are spaced and no longer watered overhead because the potential for spread is gone.
When Xanthamonas is detected you want to remove the diseased plants as soon as possible but before you do make sure to show your employees that work in the begonias what the symptoms look like. This will help them recognize it the next time before they spread it more. Remember: removing the infected plants is the key to controlling Xanthamonas.
Greenhouses with condensation drip problems are bad for all crops but since splashing water is one of the main methods of Xanthamonas spread these conditions can ruin a whole crop if Xanthamonas is present. If you find any infection be sure to move the crop to a dry spot.
Xanthamonas Begoniae is different than the Xanthamonas that infects Geraniums or other plants so you don’t need to worry about it spreading to any other plants except other begonias. The bacteria lives only in begonia tissue, but may stay dormant in a plant without showing symptoms for some time. It may also survive in dead plant parts, on the ground or on pots, for a few months, so when you throw away an infected plant it is best to throw away the pot too.
Another thing you can do to reduce spread is to make sure that the foliage is dry when you are planting or doing any grooming or pinching of the begonias. If the plants or your hands are wet and Xanthamonas is present the water will greatly increase the chance of spread. Periodic hand washing (with soap or an alcohol product or a chlorine product) when working in the crop pinching or spacing will also reduce the chance of spread ( remember to dry your hands after washing).