Dear Jim,

Looking at the photos, your young red oak (Quercus rubra) appears to have anthracnose, a fungal disease that causes areas of browning on leaf margins and smaller necrotic spots (black spots) on the leaf surface. The causative agent is called Apiognomonia. Anthracnose infections typically begin in the lower canopy and moves upwards. This is because shade and moisture are more abundant in the lower canopy. It forms fruiting structures on the underside of leaves in necrotic areas, usually next to veins. It can infect twigs causing dieback prior to bud opening. The fungus likes cool, wet springs and tends to subside during hotter, drier summer weather. In autumn, when cooler weather returns, there is often resurgence in disease development as the pathogen exploits senescing foliage (remobilization of nutrients from leaves to other parts of the tree and typically when color production is observed in deciduous trees). Resting structures then develop, which allows the pathogen to overwinter. In the spring, spores are produced from surviving vegetative/fruiting structures and the cycle repeats. As a result, management of anthracnose fungi can be very challenging/frustrating, especially when cloudy and wet weather lingers as new foliage is developing. Chemical control is not usually warranted, but foliar sprays can be effective when performed early in the season before bud break and during labeled intervals when immature foliage is most susceptible to infection. Important note, fungicides/foliar sprays protect only healthy leaf and twig tissue and don’t eradicate existing infections! Furthermore, the instructions and handling precautions of these sprays must be followed closely.

Anthracnose fungi don't present a major threat to established, healthy trees. However, in conjunction with other stresses, anthracnose can play a contributing role in tree decline. Prune and discard dead stems and branches and thoroughly remove and destroy all fallen leaves (do not place any of these substrates in the compost heap) in autumn and spring as they harbor the fungus and allow inoculum to remain at the site. Maintaining tree vigor through adequate fertilization, supplemental watering (if we are in a low water drought conditions), light mulch to help moderate soil temperatures and pruning of dead branches will help oaks to thrive despite the presence of disease. To manage your expectations, spores can travel long distances and anthracnose fungi like Apiognomonia are widely abundant in most landscape settings. As such, this makes 100% eradication of the fungus unrealistic at your site.

Please also see:  https://extension.psu.edu/oak-diseases

​​Oaks can have an extensive lateral root system that spreads horizontally out from the trunk to and well beyond the drip line, sometimes as much as 90 feet for large specimens. This horizontal root system is the primary supporter of the tree for the rest of its life. It includes the important fine roots, which absorb moisture and nutrients. Most of the Oaks root system occurs within the top two to three feet of soil.

Our literature research identifies two conditions that could be causing the lawn ring of brown, wilted dead grass around your OAK. Sometimes this is called a 'fairy ring" and is known to occur more often around OAK trees.

1. The lawn ring has been outcompeted for water by the Oak's root system. We had previously had low water conditions in the County and with the recent rain returning to a more normal level the turf ring may go away. Low soil moisture decreases bacterial activity which supports the lawn's (and tree's) access to nutrients. 

2. The ring could also be caused by soil fungi, as the lawn's or underlying root system decomposes, there are at least 60 fungi that have been identified that can cause a ring. (The research is mostly associated with golf course turf management.)

Control Recommendation: Carefully, manually de-thatch the ring area by raking out the dead lawn material and thatch and then aerating around the drip line to increase the area's access to water and oxygen. Perhaps just using a digging iron every few feet around the ring. Avoid any over nitrogen fertilization in this area. Make sure tractor blades are sharp when mowing around the tree. To help protect your Oak, always be careful to avoid any impacts around its root zone. 

Thank you for contacting the Help Desk.

Claire & Becky   

Thank you for the detailed information! Would using a mulching plug on my lawn mower be effective to dispose of the leaves? I can't imagine bagging so many leaves

Jim - sorry for the delay did not see your followup request.  Yes - great time to mulch leaves and return them to your lawn and feed your soil. 

Maybe rake some of the leaves way from the trunk flairs and outside the tree's drip line in order to minimize any impact from your tractor causing soil compression around the previous fairy ring and inside the canopy's interior root zone.