Plant Pathology Infobytes

June 18, 1998
Fatal Attraction: Southern Stem Blight and Vegetable Crops

It's generally at this time during the gardening season when southern stem blight causes problems for susceptible garden plants. Tomatoes, peppers, lima and green beans, as well as other vegetable crops, are often killed by this fungus disease.

Southern stem blight shows up in gardens following hot, humid weather, since these conditions allow the southern blight fungus to attack garden plants. The first symptom of stem blight is leaf yellowing, followed by rapid wilt and plant death.

There are several pests which may cause plant yellowing, wilt, and death of garden plants, but it's easy to determine if southern blight is responsible. A diagnostic symptom of the disease is the presence of white fungus growth on the lower stem and nearby plant debris.

This growth it most easily observed several days after a rain. Numerous smooth, round, light tan to dark brown seed-like structures called sclerotia are usually formed in the mat of fungus growth. The sclerotia generally aren't too difficult to locate and are about the same size as mustard seed.

Other than removal of diseased plants (be sure to remove the sclerotia and soil for several inches around the base of diseased plants as well), there is little that can be done to control southern blight until after the gardening season is over. To prevent southern blight from "knocking your garden plants dead" in future seasons practice the following control recommendations:

  • Remove disease plants from your garden. Don't add this type material to your compost pile.moved from the garden.
  • This summer or fall, remove remaining crop debris from the garden area following final crop harvest. This will insure you'll remove additional diseased plants you may have missed earlier in the season.
  • This should be followed by burial of any remaining crop debris by plowing the soil to a depth of at least six inches. Plowing is an important practice since it insures that carryover sclerotia are buried. Sclerotia serve as the source of future southern blight outbreaks, so burial means they won't be around to cause problems in the next gardening season. Crop residue burial has the additional benefit of helping to reduce the incidence of other vegetable diseases as well.
  • Next spring, use corn as a rotation crop for areas of the garden where southern blight was especially severe. Corn is one of the few vegetable crops not affected by southern blight.
  • Before planting, wrap lower stems of tomato and pepper transplants with aluminum foil to protect them from attack by the southern blight fungus. Check with the County Extension Office County Extension Office for details on this technique.
  • Consider using a soil fungicide such as Terraclor 75 WP at planting time. This fungicide is recommended for southern blight control on vegetable crops such as tomato and pepper.
  • During the season, avoid throwing soil against the lower stems of the plants when cultivating.
  • Control foliar diseases since the southern blight fungus tends to first grow on fallen leaves before moving on to plant stems.


Written by the late Dr. Frank Killebrew

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