Apple Scab on my Crabapple

Do you have Crabapple that lost all of its leaves early last Summer? If so, you are not alone. The culprit is a foliar disease called Apple Scab, and last year was a huge year for it. Apple scab is a fungal pathogen that causes splotched leaves, flowers, fruits, and eventually defoliation of members of the rose family. You may have also seem symptoms on your Hawthorne, Pear, Mountain Ash, Apple, or Serviceberry tree. It is especially worse following particularly cool, wet Springs, like the one we saw in 2024.

Apple scab spores float in on the wind and infect your tree’s leaves just as buds are opening up in early Spring. The spores embed themselves in the leaves while they are young and tender and have weaker defenses. Then, as the season progresses, symptoms start to show up when the weather becomes warmer. You may first notice dark spots on leaves, flowers, or fruits of trees in late Spring or early Summer, then the tree may begin to drop leaves as Summer progresses. Some trees may wind up losing every last leaf during bad years, as we saw in our area last Summer. Many Crabapples have enough energy reserves to survive a total defoliation once, but multiple years of defoliation can cause extreme stress and eventually death of trees if left untreated. The good news that we have effective treatments that can get the issue under control.

Prevention

Apple scab is treated with a series of preventative fungicide sprays that stop fungal spores from embedding in the young leaves. These are foliar sprays that are professionally applied by our arborist technicians. The first round is typically timed shortly after the young leaves start to emerge in early Spring. Subsequent rounds of spray are then applied about 10-14 days apart, with adjustments made to avoid applications during peak bloom time. Your arborist may prescribe between 2 and 5 rounds of spray, depending on the species and conditions of your tree. The spray formulations are adjusted from year to year to avoid resistance to repeated use of the same products. We also practice Integrated Pest Management methodologies and use products with minimal toxicity.

Our technicians are trained to pay attention to their surroundings and avoid spraying anything other than your trees. We gladly move birdfeeders, lawn furniture, bird baths, and we cover anything that cannot be moved. We closely watch for pedestrians, cyclists, and anyone else nearby. Weather patterns are closely watched as well. We do not spray in high winds or rain, so the exact day of your applications can often change on short notice. We are always happy to answer any questions you have about how these sprays are applied.

If you wait until you see symptoms of Scab on your tree, it is often too late to treat that year, but fret not. You can always get in touch with your arborist to schedule sprays for the following Spring. Preventative treatments are designed to protect that’s year’s foliage, so they are recommended annually.

Now is the time to sign up for preventative treatments. Contact Tree Health Management today!