Anthracnose Disease In Modesto Ash Trees

Modesto is the home of the original Modesto Ash tree (Fraxinus velutina), also known as the “Old Grandad”. It was once believed that this variety is the bastion against diseases. However, anthracnose disease in Ash trees eventually revealed that these trees have their weakness. The good news is that you can manage and treat this disease, even though eradication is usually not possible. 

Keep reading to find out more about Modesto ash tree problems and what you can do to prevent them from happening!

Anthracnose Disease in Ash Trees – Everything you Need to Know

About the Disease

Anthracnose disease in ash trees is caused by a fungus that affects many other plants too. However, specific plants, such as Modesto ash trees, are pathogen-specific hosts for individual anthracnose fungal strains. 

To be more specific, the fungus that attacks ash trees is called Gnomoniella fraxini. Its growth is promoted by cool and wet spring weather and it causes shoot and leaf blight. In addition, some trees will lose all their leaves due to the disease and premature defoliation. 

Some tree services Modesto consider that the treatment is ineffective after the symptoms are already developed. Still, chemical pest and preventive cultural management treatments may stop the disease from spreading to a certain degree. 


Infections caused by fungus continue unabated when infected leaves drop. This is why it is very important to move them away as soon as you notice the symptoms. You have to rake up fallen leaves to help break the life cycle of it and to solve Modesto ash tree problems to some degree.

Stressed and under-fertilized trees are more susceptible to this disease. We recommend hiring a tree service California company to help you with fertilizing and watering schedule during periods of low rainfall. Regular maintenance can significantly strengthen the tree against the infection. 

Water the tree with about an inch of water every week. Do so around the tree’s drip line, and follow the directions on the label when it comes to fertilizing. Prevention is the key to helping your ash trees fight off the disease and stay healthy during the whole year. 

Chemical Treatment

Chemical treatment can be very useful with Modesto ash tree problems with anthracnose. It is very effective, but you have to apply the chemicals at the right time. Most arborists recommend three applications of protectant fungicidal sprays. 

The first spraying should be of lime sulfur when buds begin to swell, just before they open. The second and third sprayings should be based on chlorothalonil fungicide mixed with water. Just follow the label directions and you should be just fine. 

The second spraying is applied when buds are open enough that they are revealing green tips. Once the buds are halfway open, you can be sure that you can apply the third spraying. 



Q: How do you treat anthracnose on ash trees?

A: You can treat anthracnose on ash trees in Modesto with chemicals and by improving their overall health. Prevention is the key to beating every type of disease. Still, regular watering and scheduled fertilizer use can successfully fight off the disease in just a few sprayings. 

Q: What are the symptoms of anthracnose?

A: The most common symptoms of anthracnose in Modesto are sunken spots or lesions of various colors on fruits, stems, and leaves. In addition, some types of infections can also develop cankers on branches and twigs. The severity of the infection will depend on the causative agent and the host. 

Q: What fungicide is used for anthracnose?

A: Experts recommend using chlorothalonil fungicide for anthracnose in Modesto. The fungicide should be diluted in water according to the label directions and applied properly. The spraying should be scheduled at specific intervals, so we recommend hiring an arborist to do it for you.

Q: Can anthracnose kill trees?

A: Anthracnose disease doesn’t kill trees in Modesto. However, repeated infections can significantly weaken the tree and make it susceptible to other, deadly diseases. In addition, refoliation can be quite tough on already stressed trees. Make sure to boost the vitality of your tree and promote new growth. 

Q: What does anthracnose look like?

A: The symptoms of anthracnose in Modesto will vary from host to host. Still, the most common symptoms are irregular spots and dead areas on leaves. These dead areas usually follow the veins of the leaves and block the necessary nutrients.

Local Tree Experts Overview

Anthracnose disease in ash trees is not deadly, and that’s what’s important. However, you should monitor your trees a few times a year for symptoms. If you notice any, make sure to contact your local arborist as soon as you can to spot the disease from spreading and weakening your tree further. Water, fertilize, and spray with a fungicide to promote the good health of your trees!

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