Answer: I wish there were a magic spray to keep insect and disease problems from occurring on all trees, but there really is not anything in general that you can use to completely protect your trees. Fruit trees are sometimes sprayed with horticultural oil or lime/sulfur in the wintertime. The oil suffocates insect eggs and the bordeaux spray can protect emerging foliage and flowers from fungal diseases. Ornamental trees may or may not benefit from preventative sprays - it all depends upon which trees you are growing and what pests they are harboring or developing as the season progresses. If you submit another question naming the trees you're trying to protect and what you want to protect them from, we may be able to provide additional information.
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