Something's eating your hosta plants. You notice ragged edges, long brown streaks or holes on the usually shiny green leaves--all signs of a possible pest infestation. Hostas are relatively resistant to insects and other pests, but nematodes, weevils, grasshoppers and snails, as well as deer and rabbits, can make a meal out of these popular perennials.
Snails and Slugs
According to the Ohio State University Extension Service, snails and slugs are the most common hosta pests. They attack at night and leave behind small holes in plant leaves. A shiny, slimy trail on the leaves is another good indication of a snail or slug infestation. To combat these pests, scatter metaldehyde bait around the plants. Some gardeners also have had success with beer traps. Place a low container filled with beer near soil level. The beer attracts the snails or slugs, which fall in and drown.
Two types of nematodes attack hostas. Foliar, or leaf, nematodes go after the leaves, while root-knot nematodes penetrate root structures. Leaf nematodes are microscopic worms that bore into leaf tissue, feed on the plant cells and lay eggs that hatch into new nematodes. These nematodes create brown streaks and spots on leaves. Foliar nematodes travel on water droplets, so keeping hosta leaves dry helps control infestations, as does removing any damaged leaves. Root knot nematodes create knots or galls on roots. They can also cause plants to wilt or stop growing. The Iowa State University Extension service says that root knot nematodes are difficult to kill with traditional nematicides. Carefully inspecting any plants before you buy or plant them is the best prevention.
Leaf beetles, grasshoppers, cutworms and adult black vine weevils will chew hosta leaves. Both grasshoppers and black vine weevils eat from the leaf's edge inward, while leaf beetles start at the center between veins. The leaf beetle's eating habits resemble snail and slug damage. Cutworms, which are moth larvae, sometimes target hostas growing in a dry, sunny garden. These pests burrow up from the ground at night to gnaw holes through young, curled-up leaves. The most harmful insect threat comes from black vine weevil larvae. These immature insects will consume the hosta's roots and crown, causing serious damage. The American Hosta Society notes that house wrens are a good natural deterrent to insect pests. Put up bird houses and supply bird seed to attract them. You can also spray Diazinon for cutworms or Sevin for other insects.
Deer and Other Animals
Deer will eat hostas--sometimes entire plants. Other animals that will consume hostas include rabbits, squirrels and voles. Rabbits will nibble on the shoots and flowers. Squirrels, according to Ohio State Extension, are most likely to eat hosta plants during a drought and sometimes will uproot plants. Voles attack the roots. Control animal predators with fencing or wire screening. To deter deer, spray deer-repellant chemicals on the hosta leaves.