White Grubs
Beneficial nematodes, a microscopic soil organism,  have shown promise for annual control of a variety of white grubs. Tall fescue, with its deep root system, is resistant to grub damage. Milky Spore bacteria may be used for long-term control of Japanese and Oriental beetle grubs. It spreads slowly  in our climate.
Crabgrass, dandelions and weeds
Corn gluten applied in early spring will inhibit weed germination. Seed with a fescue mix of grass seed to crowd out weeds. Mow late in the spring. Maintain correct pH.
Thatch
Aerate in fall and top-dress with 1/4" compost or compost tea.
Poor Lawn Conditions
Top-dress annually with 1/4" compost or compost tea. Overseed with a fescue grass blend plus clover.
Woolly Adelgids
Hemlock trees are susceptible to infestations from these insects. Spray dormant horticultural oil in early April over all branches. If necessary, spray again in early June, but avoid nesting birds. 
Poison Ivy
Apply a vinegar and lemon juice based weed killer, such as Burnout or Nature's Glory. 
Gypsy Moths
They have been controlled naturally since 1991 by a beneficial parasitic fungus.
Fleas, Ticks, Mosquitoes
Spray garlic oil or hot pepper wax on foliage around property. Avoid flowering plants, or bees will not pollinate them. Garlic oil will have a strong odor for about a day. For mosquitoes in particular, eliminate standing water on your property.

To improve lawn conditions, top-dress with 1/4" compost.