Thank you so much for looking at my plant problem! I’ve got a large property near Collingwood Ontario with about 50 pine trees growing on it. They are planted very close together in full sun. The ground is a top soil on top of gravel so most of my trees are hungry! They all seem to have this mystery mold growing on them. It’s covers the entire stump and has spread to most of the branches on all the trees. It’s growing on the top side of the branches only. I’m just wondering if you can identify the mold / fungus and let me know if it’s something I need to treat?
Thank you for contacting the Toronto Master Gardeners.
Although the image is not very clear, it looks as if your pine tree twigs are covered in lichen not mold. Lichens are a symbiosis between a fungus and either an alga or a cyanobacteria. Lichens may be an indicator of poor plant health, but they are never the cause. Lichens take nothing from trees or other substrates that they grow upon. They are simply using this spot as a place to perform photosynthesis.
If your trees are healthy, there is no cause for alarm. According to this article ” Conifer tree bark differs in chemistry from deciduous tree bark as it is more acidic with organic resins and gums. Conifer canopies tend to be denser and allow little sunlight to fall on the bark. In the case of conifer or evergreen trees , some lichens can survive in the resulting year-round partial shade. To obtain sunlight they also tend to locate on branches that are stressed or dead, which may again give the erroneous impression that they have contributed to the plant’s health condition.”
We have attached two articles below for your reference: Lichens in the Landscape
From your description it appears that your trees are planted very close together and are therfore reciving inadequate airflow which is the reason you are seeing lichen on your trees. Lichens can be controlled to some extent by improving air circulation around the plant –prune out any overcrowded branches. Abundance lichen presence concentrated on damaged wood may be a warning sign and you may need to consult a certified arborist. To find a certified professional arborist to help you with a tree problem, visit the International Society of Arboriculture’s searchable database here.
Lastly, you may wish to contact the Master Gardener group in your area awhich you can find here
Good Luck with your pine trees.
June 29, 2023