Tag leaf spotting

Another installment in our series of posts where Texas Tree Surgeons answers your tree questions. Are you having problems with your trees and want to know what’s wrong? Let us know!

Dear Texas Tree Surgeons,

A lot of my bushes, especially the red tip photinias, are starting to wilt and have reddish-brown spots on their leaves. What can I do about that?

Red Tip Photinias have long been a staple of North Texas flowerbeds and hedgerows. Hardy and fast-growing, the evergreen shrub can be trimmed to various heights and forms a good privacy barrier with its broad leaves. New growth has red leaves, giving the red tip photinia its name. Unfortunately, red tip photinias are particularly susceptible to leaf spot diseases.

This fungus Entomosporium mespili causes leaf spot on all members of the rose family, including red tip photinias. Starting as a red, brown, or black dot on leaves, the leaf spot expands outward as the fungus grows. Eventually, the red spots turn into a gray area rimmed by red. As the fungus spreads, it disrupts vascular function in the leaves, which eventually fall. The fallen leaves collect moisture at the base of the shrub, increasing fungal growth. As wet conditions continue, the fungus can spread its spores within water droplets, such as splashing from rain or irrigation. Left unaddressed, the fungus will spread throughout the photinias, causing wilting and dieback.

Environmental control

The first line of defense against fungal leaf spot, as with many fungal diseases, is to monitor watering and drainage. Fungi thrive in wet conditions of a moderate temperature, so the spring and fall are when we see the most activity. In periods of wet weather, the clay soil common to much of North Texas can hamper proper drainage, causing the area around the red tip photinias to become waterlogged. This moisture, mixed with the fallen and decaying organic material creates the ideal conditions for fungal growth. Even if the soil drainage cannot be improved, it is important to curtail watering so as not to make the situation worse.

In addition to moisture, the fallen photinia leaves contribute to the growth of the Entomosporium fungus. Keeping the area around the plants clear of debris can help slow fungal progression. In a similar way, dense foliar growth on the interior of the red tip photinias can collect moisture. Where possible, thin out dense areas to allow light and air to circulate. When trimming, make sure to remove any areas already showing leaf spot. Removed material, especially infected leaves, should be buried or disposed of in a plastic bag.

Chemical Control

Fungicides can be used to control Entomosporium leaf spot, but the process can be costly. Furthermore, treatment will be ultimately ineffective if the environmental factors are not eliminated. For valuable hedges, a continuous process of multiple-week treatments in the spring and fall may be recommended. In other situations, it can often be more cost-effective and better in the long-term to remove the affected plants and replace with a less-susceptible species. 

While there is no quick solution for red tip photinia leaf spot, we hope this information can help homeowners mitigate the damage to their shrubs, and decide if treatment or removal might be warranted. At Texas Tree Surgeons, we love trees (and shrubs! and hedges!) and we love our customers, and we always want to give our community the best, most accurate information regarding their plants. If you would like one of our arborists to come out and see how your photinias, or anything else, are doing, let us know!

Dear Texas Tree Surgeons,

My Chinese pistaches are looking terrible! The leaves are yellowing, the berries are black, and it looks like it’s dying. What’s going on?

-A.B.

For many years, the Chinese pistache (Pistacia chinensis) has been well-regarded as a landscape shade tree for urban environments in Texas. Although native to China, this species of pistache (related to the nut-bearing pistachio tree) can thrive in a variety of conditions. The Chinese pistache is a fast grower and is resistant to heat, drought, and alkaline soil, all common in North Texas. Like the native red oak, the Chinese pistache is a reliable source of fall color. The dark red berries that female Chinese pistaches produce are not only striking, but can attract birds and other wildlife. For many builders and landscapers, the Chinese pistache is a go-to choice.

This year, however, we have been seeing unprecedented dieback and wilting of leaves and berries in Chinese pistaches. Entire trees are exhibiting leaf spotting and extensive browning. Similar to the browning present in Italian cypresses the past two years, it seems that the Chinese pistache dieback is caused by a fungus. And much like the Italian cypress issues, there may not be much that can be done at this point.

Water, Water Everywhere

Recent wet weather, combined with poor drainage in clay soils, creates a “wet feet” situation in trees, where their roots are inundated with too much moisture. Trees that are not suited to wet soils are not able to regulate the high moisture level in their roots effectively. The roots then become susceptible to pests, especially fungi, which thrive in damp, poorly-drained soil. As the tree root tissue becomes waterlogged, the fungi are able to gain a foothold in the roots and begin infecting the tree internally. Eventually, the tree’s vascular system itself becomes the mechanism by which the fungal spores are spread throughout the branches, leaves, and fruit. The fungus disrupts cell function in the above-ground parts of the tree, just as it did in the roots.

What Can We Do About It?

Unfortunately, there is often little that can be done to improve overall drainage in clay soil. Still, there are some things that tree owners can do to give their trees the best chance:

• Select native species that are well-adjusted to the North Texas climate
• When planting, do not plant too deep, and follow good mulching practices
• For established trees, do not overplant the area near the root collar and inside the drip line with turf grass or other groundcover
• Consider root collar excavation (Airspading) for trees that were planted too deep
• Vertical mulching and soil aeration can help break up heavy clay and compacted ground
• Stop watering and turn off sprinkler systems during periods of heavy rain

Sometimes, despite best practices, fungal infections cannot be avoided. At the first signs of leaf spotting, or unseasonal browning or wilting, contact a certified arborist to diagnose any issues with your trees. Your arborist can suggest a plant health care program. Fungicidal treatments can be helpful, but must be timed appropriately. Once a tree shows extensive browning or dieback, it is often too late for fungicides to be effective.

If It’s Too Late…

If your trees are covered in dead berries and have dropped a lot of leaves already, it is unlikely that a fungicide would have much effect. The best thing to do would be to remove any diseased material from the tree, do as much as you can to improve drainage, and begin a fertilization program. With a good winter freeze, the fungus should die off. In the spring, reevaluate the tree for early signs of new or lingering fungal activity, and treat as appropriate.

At Texas Tree Surgeons, we love trees, and we hate to see a new problem arise that affects a common and much-relied-upon tree like the Chinese pistache. We have submitted samples to the Texas Plant Disease Diagnostic Lab and are awaiting the results. With proper identification, we may be able to better control the particular fungus in the future. We will be sure to let you know what we find out. Keep an eye on our Facebook page for updates!

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We received our results from Texas A&M. The samples we submitted from one Chinese pistache specimen showed evidence of both Phytophthera root rot and Anthracnose stress.

Phytophthera is a pathogen that causes damage to root tissue which can lead to the death of a tree. Phytophthera’s activity is enhanced by wet soil conditions and poor drainage. While fungicidal treatments can be applied, they will be of little benefit unless the underlying moisture and drainage issues are corrected.

Anthracnose is cause by a fungal pathogen, and can take advantage of plants that are already weakened by other stressors. The best method of managing anthracnose is to clean up and dispose of any fallen infected leaves or berries. Fungal sprays may be applied, but are generally not recommended during late summer or autumn, as the trees are preparing to go dormant for the winter, and the fungus should decline naturally.

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As always, please let us know if you have any tree questions. We are always happy to have a certified arborist come out and take a look a small issue to hopefully stop it from becoming a big problem!