It’s that time of the year when our Extension office gets inundated with calls about vegetable garden problems. It seems like problems are starting earlier this year. In fact, it’s so early in the season that there really shouldn’t be many insects and diseases affecting vegetables—yet. Most insects and diseases take time to build up their population to a point that damage becomes noticeable around early to mid-summer.
Interestingly, I believe many of the problems we are seeing now are associated with planting too early in the season. We caught a lucky break in April this year without seeing a late freeze event. Officially, our last frost was on April 10 according to the Rome weather station. However, early morning temperatures dipped down into the low to mid-30’s several times toward the end of April and quickly rebounded into the 70’s and 80’s during the daytime. Incredibly, we saw highs top 84F degrees on March 30 and April 6.
Many folks started planting their gardens in early April this year during the warm sunny spring days we enjoyed. This is very tempting when the garden centers are full of beautiful vegetable transplants—that were grown in a greenhouse. Unfortunately, any plants that were put in the ground in early April were stressed by the extreme fluctuations in temperatures. Also, the soil temperatures were slow to warm above 65F degrees until the last week of April. That threshold is the key to allowing summer vegetables to rapidly establish new roots and begin taking up essential nutrients.
Anything that was planted before the last week of April was likely stunted and stressed in cool, moist soil. This cool-temperature stress makes plants more susceptible to disease problems earlier in the season. Also, when vegetables are growing slowly, they often experience nutrient deficiencies. We’re seeing many vegetable samples that are stunted and nutrient deficient right now. Many home gardeners don’t put enough fertilizer on their vegetables and/or their soil pH is too low (or some cases too high) for the nutrients to become available.
A pH of 6.0 to 6.5 is recommended for all vegetables except Irish potatoes, which require a pH of 5.0 to 5.5. Most vegetables need initial fertilizer at planting time, and again after they have begun to mature. Some vegetables, such as corn, need to be fertilized by side dressing after the plants are about knee high. Vegetables are classified as light, medium or heavy feeders, based on their fertilizer needs for each group.
Heavy feeders include potatoes and tomatoes, which require a 10-10-10 fertilizer at a seasonal rate of 35 pounds per 1,000 sq. ft. Medium feeders include cucumbers, beans, squash, peppers, okra, and sweet corn, which require a 10-10-10 fertilizer at a seasonal rate of 20 pounds per 1,000 sq. ft. Southern peas are considered light feeders and only need a 6-12-12 fertilizer at a seasonal rate of 10 pounds per 1,000 sq. ft. Be sure to split the fertilizer into two or three smaller applications about a month apart during the growing season. If your soil test shows low levels of secondary nutrients such as magnesium or manganese, consider using a fertilizer that includes primary, secondary, and micronutrients. These are usually sold as “super rainbow” 10-10-10 fertilizer at local feed and seed stores. You don’t need a fertilizer with these extra nutrients every year, unless a soil test shows there is a deficiency. If you haven’t done a soil test in a few years, contact our Extension office for more information about submitting a sample to our lab at UGA. We also have several vegetable gardening publications available for free at our website: extension.uga.edu/publications. Type the word “vegetable” or the name of a specific vegetable into the site search engine to find more information. One very helpful publication (with pictures) is titled, “Troubleshooting Vegetable Production Problems in the Southeast.”