Grape Vine Disease/Affliction Identification Help?
I planted a grapevine at the beginning of the summer and it has had very little growth, all leaves remain small, and all of the early foliage has cankered, with red and dead brown spots. The garden has full sun all day, and the soil was tested last year and fertilized accordingly—all other plants do well. Any diagnosis or advice would be appreciated.
Montgomery County Maryland
The spots on the foliage are symptoms of black rot disease. This is a common fungal disease in grapes. https://extension.umd.edu/hgic/plants/diseases-grapes. There is no curative treatment for black rot once you see the symptoms. Grapes are susceptible to this disease when the youngest shoots first emerge to 4-5 weeks after they bloom. Management of black rot has to be done preventatively at the beginning of the growing season. We recommend that you follow a spray schedule in the spring and begin sprays when new shoots are 1-2 inches long. You can find the spray schedule, and recommend products, for grapes in this publication from Virginia Tech. http://pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/456-018%2003%20Home%20Fruit.pdf
In addition, clean up affected plant material and throw it in the trash (do not compost it). This will help to reduce the fungal inoculum (which could serve to reinfect the plants next year). Remove weeds from the area to improve air circulation. Removing weeds will also help to reduce competition for water and nutrients.