Spraying large trees may not be necessary as predatory insects will bring the aphid population down. The larvae do most of the feeding on leaves. The adults eat the entire leaf while larvae skeletonize the leaves. There are two generations per year.
Lace bugs cause mottling and yellowing of the leaves.
The insects are small, found under the leaves, and have transparent wings with dark veins. Poplar and willow borer bore in the trunk and may be serious on newly planted trees. In spring the insects expel frass through openings in the trunk. The frass clings to the bark. Spraying may be done in late fall or early spring and should be applied to large limbs and the trunk.