Question
My ash trees all have something eating the leaves, they appear to be a worm in
a cone shaped coat all you see is the head sticking out.They go from leaf to
ground on a thin line they seem to make. They can be seen hanging on these
lines all over the trees.

Answer
These are bagworms. Bagworms (Thyridopteryx ephemeraeformis) can be serious pests, especially in landscapes. Beginning in late May through mid-June, larvae of this native moth feed on arborvitae, junipers, pines, spruces, and many deciduous trees. Larvae build loose silken bags which cover their entire bodies. Bags are camouflaged with pieces of plant material, and may be mistaken for natural parts of the tree. Females do not look like moths (no wings, legs, antennae, eyes, or mouthparts) and remain in silken bags throughout their entire lives. When larvae are fully grown, their protective bag is 1.0 to 1.5 inch long. In late summer, male moths (black, with nearly clear wings approximately 1 inch across), emerge from their bags after pupation. One generation occurs per year.

If the bags are few in number and easily reached they may be picked off the plant and squashed. This can be done easily in the late fall when deciduous foliage has been dropped or the bits of plant material on the bags turn brown and can be easily located on evergreens. Be sure to cut the attachment silk band so that the branch will not be girdled in the future.

The bacterium, Bacillus thuringiensis (Bt), is effective against bagworms if it is used against young larvae. Applications should be made at the end of June after all the eggs have hatched and the larvae are through ballooning.

Stomach insecticides are very useful for control of bagworms. Remember that the plant foliage is to be thoroughly covered because the larvae are protected from contact by being in the silk bag. Again, early sprays against young larvae are more effective than later applications. Products registered for bagworm control are: acephate (Orthene), bifenthrin (Talstar), carbaryl (Sevin), chlorpyrifos (Dursban), diazinon, dimethoate (Cygon),  malathion, nicotine sulfate, pyrethrum, and rotenone.