Green Circle Growers Blog

How to Identify Plant Fungal Diseases

Green Circle Growers - Friday, June 10, 2011

The wet spring is taking a toll on garden plants. In many gardens, fungal diseases seem to be blooming faster than the flowers (see our previous post). The forecast of more wet, humid weather doesn’t bode well for garden lovers. Once fungus takes hold, horticulturists say that, in most cases, there is little gardeners can do but wait it out. Even though plants look unsightly, well-established plants should weather the storm without permanent injury. Removing heavily diseased plants and giving your garden a good dose of broad-spectrum fungicide early next spring should return your garden to its normal beauty next year.

Here’s how to identify common fungal diseases:

  • Anthracnose leaf blight affects the foliage of trees and shrubs but rarely causes permanent damage. Leaves may become discolored and brown spots usually appear along leaf veins. Dogwood and sycamore trees are most at risk but should survive if the fungus does not attack the stem tissue.
  • Septoria is a serious fungal disease that primarily affects vegetables and grains and can destroy plants. Plant leaves and stems will exhibit black or brown spots. Hot weather can cause plants to drop their leaves. Defoliation is particularly damaging to tomato plants. The fungus is highly contagious and infected plants should be removed promptly.
  • Botrytis, also called “gray mold,” primarily attacks flowers and can kill plants in severe cases. Identified by patches of fuzzy gray mold, this fungus also causes leaf spots, withered flowers and bud rot. Spacing plants to allow plenty of air circulation is the best way to prevent this fungus.
  • Root rot is a major plant threat. It thrives in saturated and poorly-drained soils. Sodden roots disintegrate, leaving plants with non-functioning roots. Damage may not be noticed until hot, dry weather arrives and plants collapse. Dying plants should be removed and the space replanted next year with plants from a different family.