Quaking aspen black spots dying - Ask Extension
We’ve ordered quaking aspen trees and have been battling these black spots in the leaves for the last couple years. We’ve tried been oil, fungicid...
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Quaking aspen black spots dying #868288
Asked May 13, 2024, 7:04 PM EDT
We’ve ordered quaking aspen trees and have been battling these black spots in the leaves for the last couple years. We’ve tried been oil, fungicide as soon as they started sprouting this year, ground treatments, and keeping the debris free from plants. We’ve also tried cutting off the heavily spotted leaves with clean scissors between each tree. The spots will develop within about a day or two and cover almost every single leaf. All to no avail and the trees continue to get more spots and even killed off a few of the smaller trees last year. The roots when we pulled them out were black and crumbling like they were heavily infected. We just got some new saplings this year and they started off with perfect green leaves and now they are also starting to get spots all over the leaves.
I don’t know if there is something in our grounds that are just not suitable for this kind of trees or if it’s the place we are getting the trees from. We’ve spent so much time and effort on these trees over the last three years trying to keep them alive and survive but seems like all of our efforts are fruitless. Is there a specific kind of fungicide we should be using, do we need to be doing a different ground treatment, is this kind of tree just not a suitable option for our area?
Shiawassee County Michigan
Expert Response
Good Morning,
It looks like Aspen leaf spot is caused by the fungus Marssonina. Symptoms of aspen leaf spot are dark brown or black flecks with either yellow halos or white centers on the leaves. Leaf petioles and terminal shoots may also be affected. Spots may merge to form large black patches on the leaves. The fungus overwinters in infected leaf debris on the ground and infected shoots.
Tree resistance is the best way to prevent foliar diseases. Several poplar hybrids or species are resistant to one or more of these diseases. Ask your local nursery for a resistant variety. Some aspens are resistant to leaf spots, but aspen production methods make it difficult to select trees for resistance. Because the disease rarely leads to mortality and management approaches are often impractical, management of Marssonina leaf blight is not often contemplated in forests managed for multiple objectives. In high-value sites, the most effective way to manage the disease is by planting or managing for resistant or tolerant
clones. Removing and destroying diseased material from trees and the ground may help reduce infections. Increasing space between trees may create a less favorable microclimate for spread and infection. Fungicides can be used to prevent infection, but they must be applied at bud break before infection occurs
Sanitation is an effective control for some foliar diseases. Fall removal of infected leaves, twigs and branches can reduce the amount of disease the next spring. Raking and destroying infected leaves can reduce Marssonina and Septoria leaf spot, ink spot and leaf rust. The shoot blight fungus overwinters in diseased stems and twigs, so it can be pruned out to reduce new infections.
Spraying will prevent only new infections; it will not cure leaves already infected. If an infection is developing on particularly valuable trees, or if there is good reason to believe an infection is imminent, the trees can be sprayed with fungicides. Trees that perennially have foliar diseases should be sprayed at bud break and then two or three times during the growing season at 12- to 14-day intervals. Check fungicide labels carefully since allowable uses and rates can change. Fungicides labeled for leaf spots should work well for all these diseases except for the rusts since they are in a different fungal group. Other fungicides may be required for rust diseases. Please follow label rates and directions when applying.
You can also have an arborist come out and assess your trees.
Find an Arborist (treesaregood.org)
Aspen and Poplar Leaf Spots - 2.920 - Extension (colostate.edu)
I hope this helps. Thanks for using our services.
It looks like Aspen leaf spot is caused by the fungus Marssonina. Symptoms of aspen leaf spot are dark brown or black flecks with either yellow halos or white centers on the leaves. Leaf petioles and terminal shoots may also be affected. Spots may merge to form large black patches on the leaves. The fungus overwinters in infected leaf debris on the ground and infected shoots.
Tree resistance is the best way to prevent foliar diseases. Several poplar hybrids or species are resistant to one or more of these diseases. Ask your local nursery for a resistant variety. Some aspens are resistant to leaf spots, but aspen production methods make it difficult to select trees for resistance. Because the disease rarely leads to mortality and management approaches are often impractical, management of Marssonina leaf blight is not often contemplated in forests managed for multiple objectives. In high-value sites, the most effective way to manage the disease is by planting or managing for resistant or tolerant
clones. Removing and destroying diseased material from trees and the ground may help reduce infections. Increasing space between trees may create a less favorable microclimate for spread and infection. Fungicides can be used to prevent infection, but they must be applied at bud break before infection occurs
Sanitation is an effective control for some foliar diseases. Fall removal of infected leaves, twigs and branches can reduce the amount of disease the next spring. Raking and destroying infected leaves can reduce Marssonina and Septoria leaf spot, ink spot and leaf rust. The shoot blight fungus overwinters in diseased stems and twigs, so it can be pruned out to reduce new infections.
Keep leaves as dry as possible to reduce the incidence of leaf spots:
- Irrigate in early morning so leaves can dry out.
- Keep sprinkler patterns adjusted so leaves don’t stay wet.
- Space trees apart to reduce humidity to help prevent leaf diseases.
Spraying will prevent only new infections; it will not cure leaves already infected. If an infection is developing on particularly valuable trees, or if there is good reason to believe an infection is imminent, the trees can be sprayed with fungicides. Trees that perennially have foliar diseases should be sprayed at bud break and then two or three times during the growing season at 12- to 14-day intervals. Check fungicide labels carefully since allowable uses and rates can change. Fungicides labeled for leaf spots should work well for all these diseases except for the rusts since they are in a different fungal group. Other fungicides may be required for rust diseases. Please follow label rates and directions when applying.
You can also have an arborist come out and assess your trees.
Find an Arborist (treesaregood.org)
Aspen and Poplar Leaf Spots - 2.920 - Extension (colostate.edu)
I hope this helps. Thanks for using our services.
