Growing great grapes requires some work, but the results well worth it. The flavor of a locally grown grape far exceeds that of grocery store varieties. Imagine what it would be like to harvest juicy Golden Muscats or full-bodied Concords just outside your backdoor! One of the biggest problems grape growers face, however, are fungal diseases. Here are some tips to keep fungus under control.
1. Choose a Regional Varietal
Select grape varieties hardy in your part of the country and with an innate resistance to fungal issues, such as brown rot and powdery mildew. Talk to local grape growers or your county extension office for help narrowing down a selection.
2. Give Your Vines a Hard Pruning
Properly pruning your grape vines can also stave off an onslaught of fungal issues. This practice is best done at the start of spring, in mid- to late-March. Remove all existing vines all the way back to the plant’s main trunk. If you can’t bear to remove all the vines, you can prune back to the second growth node. Because grapes fruit on new wood, the harder the pruning, the better.
When pruning, always use clean, sharp pruners when making any cuts. Disinfect them with a 10-percent bleach solution before working with another grape plant. Never work when vines are wet, as fungal spores are easily spread in wet conditions. Check that leaves and vines are completely dry before working with them. Dispose of all cut vines properly. Do not let them lie in the vineyard, as they can serve as vectors for disease organisms.
3. Increase Air Circulation
Properly spaced grape vines are less prone to fungal issues, as good air circulation allows the foliage to dry more quickly. Keep that in mind when siting any new plants. A summer pruning, timed when the fruits are about a 1/4 inch across, also increases air circulation. To do this, remove any vines covering the developing fruit clusters, as well as those shooting up and away from the plant.
4. Catch Fungus Problems Early
Be on the lookout very early in the season for signs of fungal issues. Wet spring weather promotes fungal growth, and when these conditions are present, there’s a good chance that fungal diseases will become problematic. Putting your orchard or backyard plants on a regular organic spray program early in the season is key to keeping fungal issues at bay. Although copper products are often recommended for this, I prefer using a biological fungicide based on Bacillus subtilis. One common brand is Serenade. It’s available as both a powder and a liquid, and it works to kill a large number of common fungal organisms on fruits, vegetables and vine crops. The rate and frequency of application depends on the targeted fungal organism, but all are listed on the product’s label.