Earlier this year, we shared an article that highlighted two issues that were tied to recent weather patterns and had many homeowners concerned about their oak trees - one was an insect (Oak Shothole Leafminer) and another was a fungal pathogen (Oak Anthracnose). Combined, they made for unsightly leaves that were riddled with holes and brown patches. Fortunately, both issues were more of an aesthetic concern than anything else, and neither of them required treatment or had any lasting effects on the overall health of the trees. In fact, they are both likely to occur each year to some degree and should not be reason for concern.
As we move through one of the hotter Ohio summers in recent memory, some oaks are dealing with yet another issue that is blemishing their leaves and even causing significant early defoliation. This time the culprit is a different foliar fungal issue called Tubakia Leaf Spot (pronounced “tu-bock-ee-ah”). This disease is much like the issues that we saw earlier this year in that it’s not something we need to treat and should be thought of as mostly an aesthetic issue. However, unlike the issues we saw in the spring, this one may indicate some underlying concerns that can be addressed.
Additional examples of Tubakia Leaf Spot
Heat and Drought Stress
With the heat of summer comes potential heat and drought stress for trees. If an oak exhibits signs of significant spotting and leaf drop from Tubakia, being proactive the following year and providing supplemental irrigation may help to reduce the effects of the disease. It may also be worth considering deep root fertilization as a way to help the tree regain its vigor and better handle the disease the following season.
Chlorosis
Chlorosis in an oak tree in Bexley, Ohio
Another common issue that many oaks struggle with is chlorosis. Chlorosis is a yellowing of the tree’s leaves that is often associated with high soil pH levels and can result in micronutrient deficiencies that affect the tree’s overall health and ability to withstand secondary stressors like insects, drought, and fungal diseases. It is a slowly progressing issue that causes a tree to decline over decades, and therefore often goes unnoticed by homeowners who just assumed their oak was supposed to be a little “yellow” looking. We’ve shared previous articles that go into greater depth regarding chlorosis, but it’s mentioned here because if your oak is chlorotic, the defoliation that can occur from Tubakia will likely be much more pronounced. Combined with the heat of summer, many oaks that are chlorotic and have Tubakia can start to defoliate at an alarming rate by mid-August. If this describes your oak tree, consider it a message that your tree is asking for a little TLC. Addressing the issue of chlorosis will help improve the health of your oak and improve its ability to deal with other stressors.
It’s worth mentioning that the issues discussed here can produce symptoms that an untrained eye may misinterpret as Oak Wilt. Oak Wilt is a serious systemic fungal disease that can, and typically does, lead to the decline and death of otherwise healthy oaks once infected. If you’re concerned about your oak tree, take a few photos of the leaves and send them to us. We may be able to determine what’s happening and put your mind at ease. If we’re not sure, we’ll schedule a visit to further inspect the tree. Even for trained arborists, Oak Wilt can only be 100% confirmed through diagnostic testing in a lab. If we suspect Oak Wilt, we will recommend this testing be done right away. Be careful with online searches as an attempt to “self-diagnose”. This often leads us down a very incorrect path when we do it regarding our own health concerns, and it’s typically no more accurate when we apply it to other living things. Ask the experts, it’s what we’re here for.
Walter Reins | Regional Manager, Russell Tree Experts
Walter has been an ISA Certified Arborist since 2003. He graduated from Montgomery College in Maryland with a degree in Landscape Horticulture, and has called Columbus, OH his home for nearly 20 years. Walter appreciates trees for their majesty and the critical role they play in our world.