Also known as Phytophthora
Crown Rot is caused by the Phytophthora fungus, which attacks the roots and, most notably, the crown of African Violets. African Violets are most susceptible to Crown Rot when allowed to sit in soil that is heavy and soggy. In almost all cases, Crown Rot is fatal. The best control for Crown Rot is, therefore, prevention.
These symptoms indicate that the crown is rotting. If your African Violet has these symptoms, it probably has Crown Rot.
In almost every case, Crown Rot is fatal. As heartbreaking as it may be, the best treatment is to simply throw the plant away, pot and all. For those intent on saving the plant, however, there is still slim hope with a lot of time and some fairly radical procedures. First, isolate the infested plant. If possible, move it to another room altogether. Next, you must remove any dead or dying tissue from the leaves, stems and roots. To get to the roots, remove the plant from its pot and gently shake off all the soil. Wherever you have removed unhealthy tissue, dust with sulfur to help prevent further infection. Next, repot the plant in fresh, sterilized soil. Until the plant has fully developed a new rootball, you will need to use a smaller pot size in order to minimize the risk of overwatering. When choosing a potting soil, select one that is very light and porous. An ideal potting soil will primarily consist of block-harvested, sphagnum peat moss. Before repotting, treat the soil with a fungicide, such as Benomyl. Do not overwater. At this point, your best hope is to use a self-watering device that allows you to water from the bottom. At all costs, avoid getting any water on the leaves or crown. Finally, do not begin fertilizing until the plant is well on its way to recovery. Depending on the condition of the plant, it may be four to six weeks before any fertilizer is recommended.
Prevention is always your best bet for successfully controlling Crown Rot. By adhering to the following guidelines, you will give your African Violets the best chance for eliminating any threat of Crown Rot.
Do not overwater. This is the greatest danger to African Violets. Overwatering leaves the soil soggy, a condition that is ripe for the development of Crown Rot. Water just enough to keep the soil damp. Always allow any excess water to drain. If you are using a self-watering device, which employs capillary wicking, make sure the pot is not in direct contact with the water. Also, it is strongly recommended that you only use wicks supplied by the manufacturer of the watering device.
Do not let the soil dry out completely before watering. Repeated, sudden changes in the availability of water can cause the same effects as overwatering.
Do not use a pot size that is larger than what your African Violet needs to form a tight rootball. If the pot size is too large, your Violet will not be able to absorb all the water, leaving the plant susceptible to the soggy conditions in which Crown Rot thrives.
Make sure the pot you use provides adequate drainage. If you are using a plastic pot which has no holes, you can easily add holes yourself with a soldering iron or by simply heating up a screwdriver and pushing it through the bottom of the pot. If you are using a terra cotta pot which has no holes, you can add holes with a drill. For 4-inch pots, use a 1/8-1/4 inch bit and drill from the bottom. Do not press too hard. Go slowly and let the drill do the work.
Use a light, porous potting soil. An ideal potting soil will consist of block-harvested, sphagnum peat moss. Such a potting soil allows any excess water to drain away from the roots. Be sure to pasteurize your potting soil.
Maintain good air circulation around your plants. Keep your growing area clean, and remove spent flowers and leaves as you find them.
Finally, you should strongly consider using a recommended self-watering device. Such devices use capillary action to draw the right amount of water into the soil. This prevents both overwatering and underwatering. For miniatures, there is the MiniWell (fits 1-inch pots) and the Optimara WaterShip (fits 2-inch pots). For larger African Violets, there is the MaxiWell (fits 4-inch pots) and the Watermaid (fits various sizes up to 6 inches.) Each of these self-watering devices is available at a number of hardware and discount stores. In addition, they can also be ordered online from the Selective Gardener, a mail order supplier that specializes in plant care products for African Violets.
Important Note on the Use of Pesticides
Please note that almost all pesticides are formulated for specific uses and conditions. When applied incorrectly, pesticides can cause ill health or damage to plants. Therefore, when using any kind of pesticide or chemical treatment, always apply as indicated on the product label.
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