Common Plant Diseases

• Powdery Mildew:
  You often will find powdery mildew on the leaves of squash, cucumber, and even tomato plants. Powdery mildew is a fungus; you can identify it if your plant leaves look as if they have been dusted with flour or are white. The fungi will spread and absorb the nutrients from the plants, causing the leaves to turn brittle.
• Alternaria Stem Canker:
  Alternaria stem canker is a common disease found in tomato plants. It appears as a black or dark brown lesion on the stems or fruit, and causes the leaves of the plant to fall off. Routinely check your tomato plants for the fungus. If it appears, try an organic fungicide. If disease persists, remove the entire plant to prevent spreading.
• Bacterial Leaf Spot:
  Bacterial leaf spot will occur in wet weather or watering conditions increase. It appears as spots on the leaves causing discoloration which can spread and cause leaves to die. Use a fungicide to kill the bacteria and stop the spread.
• Mosaic Virus:
  Mosaic virus can look like discoloration in your plants causing yellow, white, and green spots on your leaves. This discoloration will be raised and look like blisters on the leaves. Mosaic virus also can be indicated if your plant has stunted growth and has leaf deformities.  Since there is no cure for mosaic virus, the entire plant will need to be pulled from the garden and tools used to dispose of the plant will need to be sanitized.

Resources

You may see different plant diseases and pests in your garden depending on your location. The USDA has information on diseases and pests you may find in your garden.