As trees leaf out several pests tend to appear.
Gypsy Moth larvae will start to feed on new leaves. Severe infestations can defoliate trees quickly. Luckily cool wet weather will reduce the pest population due to disease. Trees will also recover better with adequate moisture.
Forest Tent Caterpillar is very similar to Gypsy Moth. This pest was severe in the Northern Tier Counties last year (2010)
Anthracnose Several species of trees are susceptible to a fungal disease called Anthracnose. Sycamore is the most obvious with new leaves being destroyed as the emerge. The tree continues to push out new leaves. Oak, Ash, and Maples species also are attacked by Anthracnose. During cool we springs and early summer leaves will become spotted and deformed and will fall from the tree. All forms of Anthracnose are spread by rain water splashing. Rake and destroy all fallen leaves to contain an infestation. Anthracnose will disappear when the weather warms up and dries out. The fungus remains dormant as spores which will sporulate when environmental conditions are right.