Many of the properties I maintain have mature oaks. The majority of these lawns struggle compared to areas in the same lawn that have no oaks. The grass is not very thick and barespots occur. With a little bit of research I've come to the conclusion that oaks are alleopathic and secrete from their roots a substance called coumarin. This natural pesticide damages other plants growing nearby so the oak tree will reduce competition for water and nutrients. So my question is what can be done? Is there an antidote to this coumarin? Is there a specific type of grass that does better than others in this environment? Perhaps a topdressing of compost to increase microbial activity and reseeding will help? I see the same pattern of dead spots around spruce trees as well. Possibly the same issue.