Arborvitae browning - Ask Extension
See attached photos of brown branches on approximately 6 year old arborvitae. These were planted in a row, 8 feet on center.
We tried neem oil ove...
Knowledgebase
Arborvitae browning #814903
Asked October 22, 2022, 11:32 AM EDT
See attached photos of brown branches on approximately 6 year old arborvitae. These were planted in a row, 8 feet on center.
We tried neem oil over the summer.
Is this a pest or problem? What to do? It seems primarily in one or two trees out of five.
Thank you.
Harford County Maryland
Expert Response
This looks like normal old needle/foliage drop that occurs in autumn for many evergreens. While we think of such plants as evergreen, in reality they do shed their oldest growth every year, which is usually the lowermost and/or innermost foliage on the branches. Ohio State recently published an article about this phenomenon, which is also commonly noticed on white pine because it's so prominent.
No action is needed and the browning needles will fall on their own. You mention the use of neem earlier in the season...what were you treating the plants for? Neem is only effective as a contact-kill insecticide, meaning it only impacts any vulnerable pests that it touches during application; dried residues don't have much efficacy, nor is neem a good fungicide. Neem and other types of horticultural oil can damage plants if applied during the wrong weather conditions (too hot, for instance), so make sure it's being used according to label directions. Tip browning of needles on evergreens usually indicates an issue with soil moisture, which can either be drought stress or oversaturated soil, as either condition results in roots not being able to supply the foliage with enough moisture. To know when watering is needed, feel the soil about six inches down in the plants' root zones and water well only when it's becoming somewhat dry to the touch at that depth. The first year or two a plant is in the ground (the older the plant was upon installation, the longer this period will be) it should be monitored regularly for watering needs.
Make sure no stakes or other types of ties around the trunks are constricting growth, as this can also "choke" a plant's flow of moisture and nutrients. If the trees are still staked after this much time post-planting, remove them as they are no longer needed.
Although leaf damage does not heal, the small browned tips seen in the close-up photo should be obscured over time as new growth covers it up; as they dry out they also might crumble off on their own due to wind. Overall, the plants appear to be in very good condition and shouldn't need any special treatments (no pesticides, no fertilizer).
Miri
No action is needed and the browning needles will fall on their own. You mention the use of neem earlier in the season...what were you treating the plants for? Neem is only effective as a contact-kill insecticide, meaning it only impacts any vulnerable pests that it touches during application; dried residues don't have much efficacy, nor is neem a good fungicide. Neem and other types of horticultural oil can damage plants if applied during the wrong weather conditions (too hot, for instance), so make sure it's being used according to label directions. Tip browning of needles on evergreens usually indicates an issue with soil moisture, which can either be drought stress or oversaturated soil, as either condition results in roots not being able to supply the foliage with enough moisture. To know when watering is needed, feel the soil about six inches down in the plants' root zones and water well only when it's becoming somewhat dry to the touch at that depth. The first year or two a plant is in the ground (the older the plant was upon installation, the longer this period will be) it should be monitored regularly for watering needs.
Make sure no stakes or other types of ties around the trunks are constricting growth, as this can also "choke" a plant's flow of moisture and nutrients. If the trees are still staked after this much time post-planting, remove them as they are no longer needed.
Although leaf damage does not heal, the small browned tips seen in the close-up photo should be obscured over time as new growth covers it up; as they dry out they also might crumble off on their own due to wind. Overall, the plants appear to be in very good condition and shouldn't need any special treatments (no pesticides, no fertilizer).
Miri
