Stem Canker (Stem Rot)
Stem cankers are what the name is, they form on stems from a fungus similar to white and yellow leaf spot. Weather can affect the way stem cankers can live; wet humid weather is what makes this fungus thrive. Canker fungus is caused and entered the same white and leaf spot fungus enters the plants, it enters through an open cut, wound, pruned wound, or pest infestation that has caused damage by eating leaves or chewing on the stem’s or stalks and can be transferred through rain. It can also get in through susceptible plants that have been wounded through environmental factors like animal attacks, pruning, LST (Low Stress Training), and using cutting utensils that are not sanitary that may have fungus or bacteria on them. Damage to the plant occurs in the form of a yellowish-brown discoloration on the lower portion of the stalk. Later, the leaves turn yellow and fall off, and the plant dries out and dies.They form mostly on the stems, but severe cases spotting starts to form on the leaves from internal tissue being cut of nutrients and water. In between nodes is where stem cankers start to form, and move up the plant, around the 3rd, 4th and 5th node is where it will mainly affects the plants. Stems will have brown lesions; eventually have a dark reddish-brown sunken canker in the stem. Sometimes if severe the wound may reopen and appear split in the middle of the area of the wound on the stem and can also create a buldge. The lesions can extend up the plant over 3 or 4 nodes, once this happens the plant starts to wilt from vascular uptake being cut. This gets confused with root rot when the plant starts to wilt, and leaves turn yellowish brown and or spots, because the stem canker does not show itself yet once this starts to happen. Once the stem canker has been observed and if not treated, the leaves will start to wilt with yellow, white and brown spots, similar to white and yellow leaf spot. When plants are affected by this, the plant is more susceptible to more fungus and viral infections, from air borne spores.
Prevent and Control
Preventing stem cankers is about the same way other fungus problems, making sure you treat wounds to your plant with H202, making sure your plants are free of pest’s and if you use tools to LST (low stress training) your plants pruning, and training, make sure all tools are sterilized before and after using them. Spraying your plant with fungicides in the months or times this fungus spreads. It’s very important that you catch this fungus before it gets to bad, once the damage has been done to the plant; the only way to get rid of this is to chop the plant down and treat the area that has been infected. Planting other plants near and or around this area can and will re-affect other plants when a new season starts.
Once your plant does have this, using fungicides until it is gone is crucial; if the canker has worsened foliar feeding is a must to help keep the plants vigor, strength and stamina in fighting the fungus. Stem cankers take over by slowly reducing the plants uptake and thus takes over the susceptibility of the plant and the fungus then takes over and worsens more quickly. Using anyone of these products will help control or eliminate stem cankers. (If the plant is to bad, nothing can save it and the plant must be cut down and tools sanitized to stop the spread of the fungus.) (Note: When using chemical and or organic control methods, do not spray the buds, and for health and safety reasons, stay away from spraying around the buds if all possible.)
