Question
My 3' new Susan magnolia tree has some decease with the leaves having big red spots and slowly turning to complete red and staying on the tree. The growth is very slow and all the leaves are catching this slowly. pale red spots growing on the leaves. used the fungus pesticide but no use. Can you please suggest what to do?

Answer
Sounds like a leaf spot fungi. Leaf Spot - Leaf spot diseases caused by various fungi attack magnolias. They're distinguished by yellow, brown or black dead blotches on the foliage. Often spots come together to form larger patches of dead tissue. Heavily infected leaves fall prematurely. Gathering and destroying fallen leaves usually suffice for practical control in established, mature trees. On small trees you can spray a fungicide to prevent the spots.

Spray fungicide in the spring at bud break if necessary. It will not cure infection that is already there, but it can control the spread of it. Begin spraying when the trees' buds break through. Repeat the spray three times in 12- to 14-day intervals.  If fungicides are required use a labeled product containing mancozeb or chlorothalonil.  
Check with your local nursery for a fungicide for leaf spots on trees.