Pecan Tree Fungus
We recently had a tree trimmer trim a large pecan tree and remove several clumps of mistletoe from upper branches. While he was up in the tree he noticed that the top side of the branches is covered in moss. He advised that ultimately the mistletoe and moss (both fungal) would kill the tree. The tree is old and beautiful and I would hate to lose it. He suggested we contact Clemson Extension to ask advice as to what we might be able to treat the tree with to save it. We did feed it in the fall with large tree spikes around the drip line.
Laurens County South Carolina
The mistletoe is a semi-parasitic plant which obtains minerals and water from the tree. So removing it was a good start. The "moss" is not fungal and will not harm the tree. It's not clear if this growth is moss or lichen. Either way, it is not harmful itself. It may be indicative of thinning foliage allowing more light to penetrate. When this happens, especially lichens will thrive. Thinning foliage suggests poor tree health. This could be due to foliar disease, insect infestations, drought or nutritional problems. You could send a sample of ailing foliage to the CU Plant Problem Clinic this summer, but it's difficult for a home grower to safely and effectively treat a large tree for either disease or insect infestations. Fertilizing will help to increase vigor, but it'd be best to do that according to a soil test report. You can have the soil tested through the CU Agricultural Service Lab. Hope this helps!
Meg Williamson, Diagnostician
Clemson University Plant Problem Clinic