Apple scab is a serious disease of apple and crabapple trees. Apple scab (Venturia inaequalis) attacks both leaves and the fruit itself. It doesn’t kill the tree. Scab will cause cosmetic blemishes on the fruit.
The first signs of apple scab often are not immediately noticed. Signs include:
- Twisted and puckered leaves that have black, circular scabby spots on the underside
- On the top of the leaves the spots look velvety having an olive-green, sooty appearance.
- The spots may join and cover the whole leaf.
- Severely infected leaves become twisted and puckered and may drop early in the summer.
The fruit on the trees, will get what look like scabs or blemishes on the fruit.
- Scabby spots are sunken and tan and may have velvety spores in the center. As time goes on, they become larger and turn brown and corky.
- Infected fruit becomes distorted and may crack allowing entry of secondary organisms.
- Severely affected fruit may drop, especially when young.
If Apple Scab is not addressed on infected trees severe defoliation over several years can occur weakening the tree and allowing for other vulnerabilities, like high winds, to damage or kill the tree.
This disease favors wet, cool weather that frequently happens in spring and early summer in NJ. Apple scab spores overwinter primarily in fallen leaves and in the soil. Fungal spores are carried by wind, rain or splashing water from the ground to flowers, leaves or fruit. During damp or rainy periods, newly opening apple leaves are extremely susceptible to infection. The longer the leaves remain wet, the more severe the infection will be. Apple scab spreads rapidly between 55 to 75 degrees Fahrenheit, which is very likely New Jersey spring weather.
Choose resistant varieties when possible.
- Honeycrisp, Akane, and Suncrisp have decent resistance to apple scab, but are not immune.
- Liberty, Winecrisp and Galarina and Nova Spy were cultivated to be apple scab resistant.
Steps need to be taken to treat Apple scab both to save the tree, and to prevent the spread of the fungal spores to nearby trees. Hiring the professionals at Precision Tree Landscaping to both prevent and get rid of Apple Scab will give your trees a long and fruitful life.
- Rake under trees and destroy infected leaves to reduce the number of fungal spores available to start the disease cycle over again next spring.
- Water in the evening or early morning hours to give the leaves time to dry out before infection can occur.
- Spread a 3- to 6-inch layer of compost under trees, keeping it away from the trunk, to cover soil and prevent splash dispersal of the fungal spores.
- For best control, spray liquid copper soap early, two weeks before symptoms normally appear, s and repeat at 7- to 14-day intervals up to blossom drop. Remember that the longer the leaves remain wet the more severe the infection can be.
- Spray with a fungicide when the tree’s buds are barely green at the tips. Continue spraying the fungicide at two-week intervals until the weather becomes warm and dry.
- The best fungicides available for scab control at this time of the early season are the broad-spectrum protectants.
Yes, the fruit of the apple can be eaten, but look for recipes where the apples will be peeled and cooked.
Apple Scab needs to be nipped in the bud, literally, check your trees early and often, hire right tree professionals to get the right treatment at the right time to eradicate Apple Scab from your trees. And enjoy your healthy trees.