5.22.24 Privet hedge help - Ask Extension
Our privet hedge was beautiful (4ft tall/2 ft wide with prolific growth. Hedge is 30 years old and otherwise very healthy. We have cut it back to help...
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5.22.24 Privet hedge help #869659
Asked May 22, 2024, 4:54 PM EDT
Our privet hedge was beautiful (4ft tall/2 ft wide with prolific growth. Hedge is 30 years old and otherwise very healthy. We have cut it back to help it thrive every 5 summers or so. Suddenly we noticed some yellowing and brownish spots in the leaves. When shook the branches the interior leaves quickly fall. In some places it is becoming denuded due to the amount of leaf drop. We had this last summer as well, but much latter in the summer. Hence, why we even recognized it. Last year, eventually the dropping stopped and new growth started. I tried checking for thrips and though some insects were seen there was nothing abundant. Unsure if we should use the "wait and see" method again this summer or to treat. Despite the heavy rains the soil is not too wet nor too dry.
Advice? Fungicide or insecticide and, if so, which ones? Nothing?
Baltimore County Maryland
Expert Response
We have been receiving a few reports this season (and last year) about privet hedges shedding leaves, though we have not been able to concretely identify the cause yet. As you noted, sometimes a thrips infestation contributes to defoliation, but other sources of stress could as well. The leaf spot is probably not responsible, though even if a fungicide were warranted (we do not feel that it is), it won't be able to cure an existing infection; they can only help to prevent new infections as spores land on leaves. An insecticide is similarly not recommended, both because we can't positively confirm which pest (if any) is causing damage, and because most options would involve spraying foliage, of which there is not much left to bother treating, given the circumstances. Sometimes insect-damaged foliage is more prone to phytotoxicity (plant tissue damage from chemical exposure), meaning that if it were to happen, even more leaf lesions or leaf drop could occur after treatment.
For now, it is a wait-and-see situation with regards to foregoing treatment and monitoring the plants for indications of new symptoms. Since all privets are invasive plants in our region (none are native anywhere in North America, and multiple species have colonized natural areas in Maryland), we have not studied their pest and disease issues extensively, and would recommend replacement over attempts at treatment when plants decline.
If you want to keep the hedge for now, you can try rejuvenation pruning, which is the drastic removal of all branches down to about a foot or two off the ground to force regrowth. If the root system is still healthy and vigorous, regrowth should gradually fill back in. If you have a leaf blower (since the foliage is too small to rake out), blow out the fallen leaves and dispose of them to avoid having them harbor any pests or disease spores by lying under the shrubs. Keep monitoring them for watering needs, feeling the soil about six inches deep and watering thoroughly when it becomes somewhat dry to the touch at that depth.
If you prefer to replace them, we can share ideas for replacement plants if you can provide more information about the site conditions. (For example, how much direct summer sun they get, if deer browse in the yard, what mature size they need to stay without relying on pruning, and how well the soil drains.)
Miri
For now, it is a wait-and-see situation with regards to foregoing treatment and monitoring the plants for indications of new symptoms. Since all privets are invasive plants in our region (none are native anywhere in North America, and multiple species have colonized natural areas in Maryland), we have not studied their pest and disease issues extensively, and would recommend replacement over attempts at treatment when plants decline.
If you want to keep the hedge for now, you can try rejuvenation pruning, which is the drastic removal of all branches down to about a foot or two off the ground to force regrowth. If the root system is still healthy and vigorous, regrowth should gradually fill back in. If you have a leaf blower (since the foliage is too small to rake out), blow out the fallen leaves and dispose of them to avoid having them harbor any pests or disease spores by lying under the shrubs. Keep monitoring them for watering needs, feeling the soil about six inches deep and watering thoroughly when it becomes somewhat dry to the touch at that depth.
If you prefer to replace them, we can share ideas for replacement plants if you can provide more information about the site conditions. (For example, how much direct summer sun they get, if deer browse in the yard, what mature size they need to stay without relying on pruning, and how well the soil drains.)
Miri
