Vine weevils, or Otiorhynchus sulcatus, are insects that feed on a number of flowers, shrubs and trees commonly used in landscaping. This flightless garden pest is found in North America, Asia and Europe. Adult vine weevils are approximately 0.25 inches (0.635 cm) long, making them difficult to spot in spite of the contrast that their black color has against green foliage. Signs of vine weevil infestation are easier to find than the insects themselves and can appear on different parts of affected plants, according to the stage of life of the offending pest.
The larval stage of the vine weevil can last two to 12 months. During this time, the pest will grow up to a length of 0.5 inches (12 mm), longer than the adult of the species is. Vine weevil larvae are white with brown heads and a legless body that curves into a “C” shape. Gardeners typically will find these larvae at the bottoms of plants, because the immature vine weevils feed on roots. The larvae are hardy enough to withstand the winter buried in the soil before entering the pupal, or chrysalis, stage in late winter or early spring.
After undergoing growth in the pupal stage, vine weevils emerge as adult insects. The exact timing of this varies by area, but adult vine weevils usually emerge in May, June or July. In indoor plants, particularly those kept in a greenhouse, adults might be found in early spring. Adults tend to hide in forks of branches and will devour the leaves of plants, leaving a ragged edge with crescent-shaped notches around the perimeters.
To get rid of vine weevils, gardeners should cut back on watering their plants. Any excess soil in the garden should also be removed. Overly moist soil and excess soil create a friendly environment for vine weevils. Certain species of nematodes, such as Heterorhabditis bacteriophora, can help clear up an infestation. Chemical pesticides also are available, but gardeners should read all package information carefully to ensure that their chosen product is appropriate for use on the affected plants.
Vine weevil control also must include prevention. When choosing plants, gardeners should carefully examine them for signs of infestation and purchase only those that appear to be pest-free. Trimming branches that touch other plants or the ground is a good way to prevent the spread of vine weevils from neighboring gardens, as is wrapping any sort of sticky material around the trunk or stem for at least 6 inches (15 cm) up from the ground. These pests cannot fly, so they will then have no way to affect plants that have received this preventative care.