Dry rot in plants is caused by a fungus, typically the Phytophthora or Fusarium fungi. Dry rot affects many garden and vegetable plants, including potatoes, gladiolus and geraniums. By knowing the signs and symptoms of root rot, you can spot it and discard the affected plants before it spreads to your other plants. The fungus can be spread easily, including through the splashing of rain from one plant to another.
Observe plant growth. At times when your plants are getting enough water and food and they should be actively growing but are not, growth may be affected by dry rot.
Look at the stature of your plants and their foliage. They can become limp, bend and possibly fall over. Their foliage can wilt as well when suffering from dry rot, especially during hot weather, according to University of Maine Cooperative Extension.
Examine the stems of the plants. They can turn brown, soft and mushy. You might also notice some white or pink growth or dark spots there as well. The dry rot will work its way from the bottom of the plant up to the top.
Notice any difference in color leaves or flowers and any fruit. Plants with dry rot can grow darker leaves and have darker than normal flowers. Typically, though, the foliage begins to yellow beginning at the tips of the leaves and the flowers are smaller and do not open all the way. Fruit closest to the base of the stem can also decay, beginning on the side nearest the ground.
Look at the roots or root structures (such as potato tubers). Black, brown, decaying, dry, crumbly and mushy areas are all signs of root rot. So is the fungus itself, which can present itself in a multitude of colors including white, red and yellow. If your plant was bent over, it will most likely bend over away from the infected side of the roots. Cut open a sample root structure with a knife to check for these symptoms, especially before planting a box full of root structures like gladiolus corms that were stored for the winter.