Question
I have about 30 pine trees at my house (I live in Fredericksburg, VA). Many (if not all) of the pine trees have a recent appearing pine cone (about 1 inch) dangling from the branch that contains a larvae. Inside is a litle worm. Local plant folks told me they are grubworms, and I can pick them off the tree & dispose of them. I can do that for smaller trees, but at my age I can't see getting to the taller trees (no matter what, it will take days to pick 'em off)
Questions 1) all articles I've read talk about grubworms in the lawn. Do these sound like grubworms? 2)what type of spray can be used to get to the taller sections of tree to rid these grubworms. 3) can they kill the tree?
thank you

Answer
The common bagworm, Thyridopteryx ephemeraeformis (Haworth), is an interesting caterpillar. The most commonly observed form of this pest is the spindle-shaped silk bag camouflaged with bits of foliage, bark and other debris (Fig. 1). Completed bags range from 1-1/2 to 2-1/2 inches long. The larva within the bag is brown or tan, mottled with black, and the bee-like adult males have clear wings and fur covered bodies. The females remain larva-like and do not emerge from the bag. The larva may stick its head and front legs out of the top of the bag to feed and move. When disturbed, the larva immediately pulls its head into the bag and holds the opening closed. Mature larvae may stay on their host plant or drag their bags some distance before firmly attaching the bag for transformation into the adult stage.

The bagworm occurs in the eastern United States from New England to Nebraska and south through Texas. The larvae seem to prefer arborvitae and red ceder but many other conifers and deciduous trees are attacked. These include: pine, spruce, cypress, juniper, willow, black locust, sycamore, apple, maple, elm, poplar, oak, and birch.

Cultural Control-Mechanical Hand Picking 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.

Chemical Control-Insecticide Sprays 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, rotenone.

These are not the same insect that is in the grass. No they will not kill the tree but will eat the foliage and if they eat all the nedles off it can cause die back and growth loss.