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I just wanted to thank you all again for the quick response last week. The team did an excellent job. ” - Terry B.

Do Your Trees Have Spots? Could be Tabukia Leaf Spot

Have you noticed dark brown spots on the foliage of you oak tree leaves? It could be a fungal disease called Tubakia leaf spot. This fungal disease occurs in a wide variety of tree species, however it is most commonly found in oak trees; especially those in the red oak family. Tabukia leaf spot can also infect elm, redbud, ash, pecan and maple trees. While we don’t want you to get overly worried about this particular disease, as its effects are typically minor in healthy trees, you should keep an eye out for it. Especially if your trees are already stressed due to drought, pests or other issues.

If an infection of Tabukia leaf spot spreads intensely around the entire canopy of your tree, it can eventually weaken your tree, making it susceptible to new health problems.

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“This fall it would be optimal to rake up and discard infected foliage to reduce the risk of inoculating again next Spring.” Says Ken Smith, PTS Arborist. Ken took this photo of an infected red oak in Dallas this week.

What is Tubakia Leaf Spot?

Tubakia leaf spot disease is caused by the fungal species Tubakia dryina. The fungus can overwinter on foliage that remains on your tree and also on leaves that have fallen to the ground. As your tree sprouts new growth in spring and summer, the fungus can infect the new growth.

What Causes It?

The cool, wet spring months encourage the infection to spread; however, you may not notice the disease during this time. By July and August you’ll start to see the brown spots showing up more predominantly. The very wet weather we had this past spring brought on many fungal diseases and we’re now seeing their effects.

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Our urban forestry specialist, Micah Pace, snapped this closeup of Tabukia leaf spots on a red oak tree. Look for the tan centers, brown outline and yellow “halo” around the spots.

Poor air circulation also encourages fungal diseases such as Tabukia. If the tree canopy is overcrowded, selective pruning to improve air flow can help reduce the disease if your tree is heavily affected. Proper watering also goes a long way: Too much water and fungal diseases become more active. Yet, not enough water puts your tree under stress and susceptible to infection.

What Damage Does it Do?

In late-summer, you’ll begin to notice small to large dark brown spots on leaves with a dark brown border and yellow halo around the spots. You may also see lesions along the leaf veins. If the damage progresses, it can eventually cause wilting followed by defoliation. Tubakia leaf spot is sometimes confused with anthracnose. However, visible signs of anthracnose begin to show in late-spring, versus late-summer. To the untrained eye, it can also be mistaken for deadly oak wilt disease. Be sure to have an experienced certified arborist inspect your tree for the right diagnosis.

Ken Smith, Preservation Tree Certified Arborist, recommends that you attend to the overall health needs of your red oaks to prevent further stress. “Focus on the healthcare of the infected red oak to reduce the stress from Tubakia leaf spot.” he says. “Make sure that your red oak is not being over or under watered. Utilize 2-3 inches hardwood mulch between the trunk and the drip line to maintain soil moisture at optimal levels and to increase beneficial microbial activity in the critical root zone.”

If your tree and soil need a natural boost, be sure to check out our SEASONS program and ask about regular tree-check ups to keep your trees happy and healthy.



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Posted: October 5, 2015