Aluminum toxicity in trees
We're not sure what you are implying. We do not know of aluminum spraying.
The gray-green growth on the trees in your photo is lichen, an organism that is part fungus and part algae. It does not kill or infect trees. It merely uses trees for support.
Thank you for replying. Something is killing the trees in Maryland at an alarming rate. Morgan Run NEA may well be barren in the near future, at this rate. What would be your guess what the spray patterns are in the attached image?. In case the image won't load- it looks just like this link
More preliminary information here:
The 'spray patterns' in your photo are not chemical trails, but what we call contrails-- essentially water vapor clouds left by passenger jets.
This Washington Post article does a good job explaining: https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/10/03/what-really-comes-out-of-an-a...
As far as trees dying, that may be, and for multiple reasons- for instance the ash trees in our area are being killed by the invasive Emerald Ash Borer. Others, like some oaks, are having some difficulties with diseases/pests/environmental issues that can cause decline or death...but overall there is nothing that is wiping out our forests. Probably the biggest concern for future forests is the overpopulation of deer, who eat young trees, and growth of invasive plants that take precious space and resources from our native plants.
For what it's worth, the lichens growing on the trees in your photo are not only lovely, but are an indicator of good air quality.
Here's more about them: http://extension.umd.edu/learn/i%E2%80%99m-lichen-it-peak-season-lichen-peeping