Knowledgebase
Brown leaf spots on Apple tree #869378
Asked May 20, 2024, 10:23 PM EDT
Lane County Oregon
Expert Response
There are a few fungal pathogens (Alternaria alternata, Stemphyllium, and Aureobasidium) that have been found in western Oregon that cause leaf spots. The spots typically start as small purple or brown spot that grow into bigger spots with a light brown center and dark purple border. The spots are observed in the same location on both sides of the leaves. This looks similar to frogeye leaf spot (Botryosphaeria obtusa), but this has not been detected on apples here in Oregon. Generally, no control measures are required since it does not affect the fruit. You can prune out infected limbs, and rake up and dispose of fallen fruit and leaves and any mummified fruit that remains on the tree at the end of the season. Other than that, try to keep the tree healthy. Make sure you are pruning properly, and that the tree has water during the dry summer months. With regards to the leaf curl/cupping, that can be a number of things, including under or over watering, extreme temperatures, nutrient deficiency, insects like aphids or mites, or fungal diseases like apple scab, among other issues. Make sure the trees are receiving sufficient water and that you have well-drained soils. We have had some low nighttime temperatures recently, but typically the tree would recover once the weather event has passed. Most likely it is a water issue, but I suggest you inspect the leaves for aphids or webbing (spider mites). Look for symptoms of apple scab (and keep an eye on the leaf spots to see if they grow or change in appearance). If you see additional symptoms or a change in symptoms, you can reply to this and send a few more photos.