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How to Rid Oak Trees of Green Fungus

Lichen/gray background image by Bluebird from

If you have oak trees in your lawn or landscape, chances are you have seen the unsightly green fungus-like growth on the trees trunk and bark. This light green growth is not entirely a fungus, but is a lichen, which is a symbiotic relationship of fungus and algae. Although lichens will not harm your tree, when left to grow undisturbed, the lichens will quickly cover the entire tree with a green, mold-like substance.

Use a bristle brush with stiff bristles to scrub away the lichen from the tree. Do not apply pressure to the brush, and you will not damage the oak's bark.

Spray the oak tree with water to soak the lichens. Scrub the tree's bark again, to remove any leftover lichen from the first scrubbing.

Cut away any branches that have lichen growing on them. Lichens begin growing on oaks because the tree's foliage is thin enough to allow light to reach the trunk and branches. Thinning out affected branches will promote new, thicker growth of the tree. Use garden loppers to cut away the branches flush with the main branch or trunk.

Spray the oak tree with a copper-based fungicide to prevent the lichens from reoccurring. You can purchase a copper-based fungicide at a garden specialty store.

Rid Oak Trees Of Green Fungus

That unsightly green fungus growing on your oak tree's bark is actually lichen, which is a combination of fungi plus algae. The lichen's presence indicates that your environment is free from pollutants. Lichen won't harm your oak tree, but it does indicate weak foliage cover, since sun promotes lichen growth. Scrub the lichen with a stiff-bristled wire brush to dislodge it from your oak tree's limbs. Cut off affected branches with anvil pruners if the damage is on limbs, not on the trunk. Treat your oak tree with a copper-based fungicide that is approved for use in your area, as horticulturists from Texas A & M suggest. Check with your local county extension office for a list of approved fungicides.

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