Answer: Magnolias are generally insect and disease free so I'm concerned that your tree is stressed which makes it susceptible to problems. Scale insects can attach themselves to twigs and branches and they look like little tufts of cotton. Spidermites can leave webbing. Both can be controlled with horticultural oil (read and follow label directions). Make sure your tree is getting adequate sunlight and that it is planted in well draining soil. Water deeply once each week to ensure it has enough water. I'd prune away the affected parts of the tree both to open it up to better sunlight penetration and to remove insect eggs that may be present. Hope this helps!
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