It is prime time for the early vegetable harvest for gardeners and farmers alike in North Georgia. However, if you venture out to the garden one cool dewy morning and notice that your plants have not fared as well as you expected, here are a few common ailments that may be causing trouble.
In tomatoes, two of the most common reported ailments are blossom end rot and late tomato blight. Blossom end rot is not actually a disease, rather it is a nutrient deficiency common in tomatoes. It occurs when the tomato fruit does not get enough calcium to aid its growth. The fruit becomes soft at the blossom end, and is then susceptible to a secondary infection, causing loss of the fruit. The best way to fix this problem is to add calcium to the soil, using products like lime or gypsum prior to planting, or by calcium nitrate fertilizer after the problem is noticed. If you have blossom end rot, a soil test before applying fertilizer is a good idea to see how much calcium should be added to the soil.
Late blight will also begin to affect tomatoes this time of year as the growing season is at its warmest. It is caused by the Phytophthora fungus. Signs of late blight are yellowing to brown dead spots on the leaves, stems and fruit of tomatoes. Plants that are treated earlier in the progression of this disease are likely to survive it, although they may not produce as well. The best treatment for late blight is to remove plants that have excessive damage (and be sure to burn them or tie them in a trash bag and throw them away) and spray the rest of them with a fungicide listed for late blight on tomatoes, such as Daconil or Bravo (chlorothalonil is the active ingredient).
On vegetables like squash, cucumbers, gourds, zucchini, beans and peas, mildew is a common disease that slows production and makes the plant less healthy. There are two common types in North Georgia: Powdery and Downy mildew. Powdery mildew is identified by large gray-white patches on the upper side of the leaves, whereas downy mildew causes many smaller light green to yellow patches on the leaves. The treatment for both diseases is the same: Remove heavily damaged plants to the burn pile or garbage, and spray with Daconil or Bravo (chlorothalonil is the active ingredient).
Before using, any pesticide always read the label and follow its instructions fully. The label is the law.
Another problem during extended wet periods of the growing season is root rot. This disease can affect most plants, but there are different groups of fungi that cause it depending on the plant. Common symptoms include an unhealthy-looking plant, combined with gummy, black roots, and a stem that is easily broken from the ground at the base. The reason the infection begins is usually due to excess moisture in the soil, or inadequate drainage of the soil. For the vegetable garden, the most effective way to control it is to prevent it. If you planted something there last year that got it, plant that thing in a drier area of the garden next year. If you use mulch, while it has many benefits, it may be holding too much moisture in the soil. When you water plants, remember to water deeply and less frequently, and let the soil surface become dry for a day or two before watering again.
If you suspect any of these ailments to be troubling your garden, or have any other questions or concerns related to agriculture, landscape or natural resources, please feel free to contact your County Extension office or email Jacob.Williams@uga.edu.