Crabapple scab disease develops from a fungus. It is the most common disease among apples and crabapples in Minnesota. Learn how to keep your trees healthy and scab-free.
Clean up leaf litter to help prevent crabapple scab
The fungus (Venturia inaequalis) can be a serious problem
The fungus (Venturia inaequalis) can be a serious problem where spring weather can be humid.
- Mid-season leaves appear to turn yellow with velvety black spots 1/4 inch or more in diameter.
- Leaf drop usually follows by midsummer.
- In winter it spreads among the fallen leaves.
- In the spring, spore producing structures in dead leaves continuously discharge into the air and blow onto the new foliage and flowers.
- The cycle repeats until the wood becomes affected.
- Infections grow into spots that can produce more spores within 9 to 17 days.
- Spores are spread by wind, splashing rain or irrigation throughout the tree canopy or to neighboring trees.
- The infection cycle can repeat many times throughout the growing season whenever leaves remain wet for several hours.
Controlling Crab Apple Scab
- Pick up all leaf litter around trees in fall.
- As new foliage appears in spring, spray the tree with a fungicide like Bonide's Fruit Tree Spray as directed. There are some species that have been bred to be immune to apple scab, do not use a fungicide on them. Know what type of crabapple you have.
- Keep your trees healthy by fertilizing with a "Ross" root feeder, a deep feeding system.
- Don’t overcrowd your trees. Allow them room for air movement.
- Prune to allow spaces between the branches, again allowing air movement for quicker drying.
- Remove suckers and upright and water sprouts at the base of your tree.
Crabapple ‘Royal Raindrops’
The experts at Gertens are always available to answer your questions!