European Hornbeam brown leaves - Ask Extension
Hello. As shown in the pictures attached, the newly planted European hornbeam has brown spots and margins all over the place. Could you please let me ...
Knowledgebase
European Hornbeam brown leaves #885570
Asked September 17, 2024, 12:48 PM EDT
Hello. As shown in the pictures attached, the newly planted European hornbeam has brown spots and margins all over the place. Could you please let me know what it could be, bacteria? Fungus? And is there any treatment available? It had some brown spots when I bought it, but became much worse only three days later.
Howard County Maryland
Expert Response
This looks mainly like scorch, a symptom of roots staying too dry (usually, though over-watering can also cause it). A very minor amount of fungal leaf spot infection might be present (and if so, we can't determine which fungus may be responsible), but nothing that needs to be treated and which is not concerning, especially given how soon leaves will be shedding for autumn/winter. Is the tree being monitored for watering needs closely? Newly-planted trees often need watering at least once a week, if not more often, depending on soil drainage and weather. The linked page provides guidance for watering. Was the tree's root ball loosened up well prior to planting (if grown in a pot) or was any burlap or cage/ties around the root ball removed prior to planting (if sold burlapped instead of potted)? If not, that can hamper the establishment process and make watering (and monitoring for watering as well) more difficult to do without accidentally over- or under-watering the root zone.
When plants contract leaf spot infections, they are almost always minor in terms of their impact on long-term plant health, and no fungicide can cure them. (For the few leaf spots caused by bacteria, fungicide rarely has any impact on them, because they are very different organisms.) While fungicide use sometimes will suppress infection if used preventatively at the start of the growing season, they usually require multiple re-applications and don't always work fully (if rain interrupts a spray schedule, for example, allowing infection to take place). Not only would thorough coverage of all plant surfaces be needed for best efficacy of such a spray, but residues may risk harm to pollinators or other organisms, so for these reasons, we usually do not recommend their use.
Fortunately, trees in particular rarely contract leaf diseases that pose more of a threat to their overall health than just a temporary eyesore when symptoms are widespread, and European Hornbeam doesn't tend to be vulnerable to many significant pests or diseases. Keeping plant stress to a minimum, like alleviating drought by watering as needed, will also help to discourage those pests and diseases that can take advantage of plants under stress.
Miri
When plants contract leaf spot infections, they are almost always minor in terms of their impact on long-term plant health, and no fungicide can cure them. (For the few leaf spots caused by bacteria, fungicide rarely has any impact on them, because they are very different organisms.) While fungicide use sometimes will suppress infection if used preventatively at the start of the growing season, they usually require multiple re-applications and don't always work fully (if rain interrupts a spray schedule, for example, allowing infection to take place). Not only would thorough coverage of all plant surfaces be needed for best efficacy of such a spray, but residues may risk harm to pollinators or other organisms, so for these reasons, we usually do not recommend their use.
Fortunately, trees in particular rarely contract leaf diseases that pose more of a threat to their overall health than just a temporary eyesore when symptoms are widespread, and European Hornbeam doesn't tend to be vulnerable to many significant pests or diseases. Keeping plant stress to a minimum, like alleviating drought by watering as needed, will also help to discourage those pests and diseases that can take advantage of plants under stress.
Miri
