Concern about Hawthorn tree - Ask Extension
I planted a hawthorn tree in my yard this spring. It has been doing well but I now see that the leaves are turning brown and lacy. What is going on...
Knowledgebase
Concern about Hawthorn tree #840734
Asked July 14, 2023, 4:52 PM EDT
I planted a hawthorn tree in my yard this spring. It has been doing well but I now see that the leaves are turning brown and lacy. What is going on with the tree and can it be treated?
Thank you!
Wicomico County Maryland
Expert Response
This is chewing damage from an insect, and given the style of damage (skeletonization of the foliage) and time of year, adult Japanese Beetles or one of their scarab-family relatives is likely. Japanese Beetles are often seen during the day whereas several other scarab beetles tend to feed at night, so if you don't see any obvious culprits hanging around on the tree during the day, check it after dark with a flashlight. Another possibility is caterpillars, though they tend to be visible either in groups or webbing when damage is this prominent.
We discourage pesticide use on trees, especially native species with benefits to the local ecosystem like Hawthorn provides, but a few lower-toxicity insecticides might be effective to prevent further damage. Even so, this is only an eyesore with regards to the plant's long-term health as beetle feeding like this does not cause them serious harm and does not require treatment.
The fruits and a few leaves are exhibiting a rust infection, a very common fungal disease that many members of the rose plant family (Hawthorn, Serviceberry, Apple, Crabapple, etc.) can contract. Prevention of infection via fungicides would be needed each spring (over the course of several applications) as the rust spores are blowing around off of infected wild junipers, but this is not practical and could risk harming pollinators visiting the Hawthorn blooms around the same time. Although the spread and severity of plant fungal diseases is highly weather-dependent, Hawthorns and other host trees can be infected routinely each year but not necessarily suffer many consequences other than a mild eyesore if spores on fruits or spots on leaves are abundant. A fungicide cannot cure an existing rust infection, so once spores appear on the Hawthorn host during the growing season, nothing can be done for the rest of that year.
Miri
We discourage pesticide use on trees, especially native species with benefits to the local ecosystem like Hawthorn provides, but a few lower-toxicity insecticides might be effective to prevent further damage. Even so, this is only an eyesore with regards to the plant's long-term health as beetle feeding like this does not cause them serious harm and does not require treatment.
The fruits and a few leaves are exhibiting a rust infection, a very common fungal disease that many members of the rose plant family (Hawthorn, Serviceberry, Apple, Crabapple, etc.) can contract. Prevention of infection via fungicides would be needed each spring (over the course of several applications) as the rust spores are blowing around off of infected wild junipers, but this is not practical and could risk harming pollinators visiting the Hawthorn blooms around the same time. Although the spread and severity of plant fungal diseases is highly weather-dependent, Hawthorns and other host trees can be infected routinely each year but not necessarily suffer many consequences other than a mild eyesore if spores on fruits or spots on leaves are abundant. A fungicide cannot cure an existing rust infection, so once spores appear on the Hawthorn host during the growing season, nothing can be done for the rest of that year.
Miri
Thank you for this information. I don't see any active eaters during the day, so I will check tonight. I prefer not to use pesticides and fungicides. Given what you have said, do you think doing nothing is a reasonable approach? I am laying out a pollinator garden right next to the tree and I don't want to negatively impact any pollinators that will be there.
Thank you. Maggi
Hi Maggi,
Yes, doing nothing in this case is a reasonable approach and is the best way to avoid any accidental harm to pollinators in the garden. It's possible the leaf damage will worsen for a little while longer while the insects in question (beetles, caterpillars, whichever they prove to be) are out, but as long as the tree's roots remain healthy and the trunk undamaged (from other injuries, as these leaf-chewing insects won't cause other problems) it will leaf back out normally next year. The closer we get to autumn, the less likely the tree will produce any more new and replacement leaves for this year, but that's normal and not concerning, just a short-term aesthetic issue.
Miri
Yes, doing nothing in this case is a reasonable approach and is the best way to avoid any accidental harm to pollinators in the garden. It's possible the leaf damage will worsen for a little while longer while the insects in question (beetles, caterpillars, whichever they prove to be) are out, but as long as the tree's roots remain healthy and the trunk undamaged (from other injuries, as these leaf-chewing insects won't cause other problems) it will leaf back out normally next year. The closer we get to autumn, the less likely the tree will produce any more new and replacement leaves for this year, but that's normal and not concerning, just a short-term aesthetic issue.
Miri
