Some worms are beneficial to garden soil. Earthworms, for example, till the earth while leaving behind valuable nutrients. On the other hand, some other species cause destruction and death to garden plants.
Adult cutworms are actually a type of moth. Both adult and larval cutworms are dangerous to garden plants. According to J. Kenneth Long from the Pennsylvania Integrated Pest Management Program, adult cutworms eat all parts of the plant, but the larvae burrow under the ground and attack the plant at the surface. This eventually kills the plant.
The Texas Cooperative Extension indicates that white grubworms are larval Junebugs, or June beetles. These grubs damage lawns and gardens from beneath the soil by devouring the root base of grasses and plants. White grubworms are usually shaped like the letter "c" and have three pairs of legs, according to the extension's website.
The root-knot nematode is a species of microscopic roundworm. It feeds on the root systems of plants and causes knot-like growths and swellings to form on the roots. These growths interfere with the plant's ability to absorb nutrients and water. Infected plants have stunted growth and wilt easily, according to Mary Olsen of the University of Arizona College of Agriculture and Life Sciences.