How to Cure Black Rot in Grapes
For an avid grape grower, the term black rot has a negative connotation. Black rot (Guignardia bidwelli) is a fungal disease that occurs in grapes grown in a hot and humid climate. This fungal disease has the ability to ruin an entire crop of grapes if it is allowed to spread unchecked. Fortunately, there are both cultural and chemical ways to rid your plants of this disease.
Look for characteristic dark circles on the leaves, dark raisin-like berries and lesions on the leaves and shoots of the grapes to confirm it is black rot. Before you can begin curing the rot, you must diagnose that what you are dealing with is in fact black rot.
Cut off the obviously affected parts of the grape vine with a sterile knife. Remove all spotted leaves and the black, mummified grapes. Be extremely thorough and make sure you remove all parts of the plant that are affected by the black rot.
Place fans in the growing area to keep the plants dry. This will help prevent the rot from spreading to other sections of the plant and will help dry out the newly cut parts of the plant. Black rot is quite contagious and is easily spread by water dripping from one affected part of the plant to another. Drying the plants as quickly as possible after watering or rainfall helps keep the disease in check.
Apply a paste of cinnamon mixed with cooking oil to the remaining tissues of the plant. This paste -- when applied to the newly cut sections of the plant -- seals the wound and keeps it dry.
Apply a fungicide, such as myclobutanil or captan according to the directions on the label.
Re-apply the fungicide at two-week intervals until the black rot has been cured. In the meantime, carefully examine the plant and use a sterile knife to remove any additional affected areas. Apply the fungicide paste to the new cuts to help them heal.
Things You Will Need
Fungicide (myclobutanil or captan based)
Elyse James began writing professionally in 2006 after deciding to pursue a career in journalism. She has written for "The Algonquin Times" as a general assignment reporter and published blogs and articles on Webcitybeat. James holds a Bachelor of Journalism from the University of Ottawa.