Apple trees are a beloved addition to many gardens and orchards, providing beautiful blossoms in the spring and delicious fruit in the fall. However, they are susceptible to a variety of pests and diseases that can affect their health and productivity. If you’ve noticed something amiss with your apple tree, it could be due to one of several common issues. Let’s explore some of the most prevalent problems: ambrosia beetles, fire blight, powdery mildew, and cankers, along with how to treat each of them. Continue reading to learn answers to the frequently asked questions: what’s wrong with my apple tree?

Ambrosia Beetles

Ambrosia beetles are small, invasive insects that bore into the wood of apple trees, creating tunnels where they cultivate fungal gardens for food. The presence of these beetles can cause significant damage, leading to wilting, dieback, and even tree death.

Signs of Ambrosia Beetle Infestation:

  • Small entry holes in the bark
  • Sawdust-like frass (insect excrement) around the base of the tree
  • Wilting or yellowing leaves


  1. Monitoring and Early Detection: Regularly inspect your apple trees, especially in early spring when beetles are most active.
  2. Pruning: Remove and destroy infested branches to prevent the spread.
  3. Insecticides: Use insecticides specifically labeled for ambrosia beetles. Apply treatments early in the season when beetles are active.
  4. Tree Health: To reduce susceptibility, maintain tree health through proper watering, fertilization, and mulching.

Fire Blight

Fire blight is a bacterial disease that affects apple trees, causing branches to appear scorched. It spreads rapidly during warm, humid weather and can devastate an orchard if not controlled.

Signs of Fire Blight:

  • Blossoms, leaves, and twigs that appear burned or blackened
  • Oozing cankers on branches
  • Shepherd’s crook appearance (curved tips of branches)


  1. Pruning: Remove infected branches at least 8-12 inches below the visible symptoms. Disinfect pruning tools between cuts.
  2. Antibiotics: Apply a copper-based or streptomycin spray during bloom to reduce infection rates.
  3. Resistant Varieties: Plant fire-blight-resistant apple tree varieties when possible.
  4. Sanitation: Remove and destroy fallen leaves and debris to reduce sources of infection.

Powdery Mildew

Powdery mildew is a fungal disease that coats leaves, buds, and fruit with a white, powdery substance. It thrives in warm, dry conditions and can weaken apple trees, reducing fruit quality and yield.

Signs of Powdery Mildew:

  • White or grayish powder on leaves, buds, and young fruit
  • Curled or distorted leaves
  • Stunted growth


  1. Fungicides: Apply fungicides labeled for powdery mildew at the first sign of infection. Reapply as recommended.
  2. Pruning: Remove and destroy infected plant parts to reduce spore spread.
  3. Spacing and Air Circulation: Plant trees with adequate spacing and prune to improve air circulation, reducing humidity around foliage.
  4. Resistant Varieties: Choose apple varieties that are resistant to powdery mildew.


Cankers are dead areas on the bark of apple trees caused by fungal or bacterial infections. They can girdle branches or trunks, leading to dieback and potentially killing the tree.

Signs of Cankers:

  • Sunken, discolored, or cracked areas on the bark
  • Oozing sap or gummy substance
  • Dieback of branches above the canker


  1. Pruning: Remove and destroy infected branches during dry weather. Cut several inches below the canker.
  2. Fungicides: Apply fungicides as a preventative measure, especially after pruning or injury.
  3. Tree Health: To reduce susceptibility, keep trees healthy with proper watering, fertilization, and pest control.
  4. Avoid Wounds: To prevent infection entry points, minimize wounding from pruning, mechanical damage, or pest activity.

Caring for an apple tree requires vigilance and timely intervention to address pests and diseases. You can keep your apple trees healthy and productive by understanding the signs and treatments for ambrosia beetles, fire blight, powdery mildew, and cankers. Regular monitoring, proper cultural practices, and the use of appropriate treatments are key to managing these common issues. With attentive care, your apple trees can continue to thrive and provide bountiful harvests for years to come.