Pest identification and confirmation—Common weevil species
Weevils, or snout beetles (family Curculionidae) feed on various plants as adults and larvae. There are more than 1,000 species of weevils in California.
Identification
Adults have mouthparts that taper into a relatively long, narrow snout. Adults of many species are brown to gray including cribrate weevil (Otiorhynchus cribricollis), Fuller rose beetle (Naupactus [=Asynonychus] godmani), and vegetable weevil (Listroderes difficilis), which sometimes (for example when feeding on citrus) can be distinguished by shape and orientation of their head.
Agave and yucca weevils feed inside Agave and Hesperoyucca (=Yucca) species as larvae. This is an adult agave weevil, which closely resembles the yucca weevil. |
Adult black vine weevil, which as adults and larvae feed on numerous species of herbaceous and woody plants. |
Adult white pine weevil. Several species of conifer bark and twig weevils feed on Douglas-fir, pine, spruce, and true fir. |
Cribrate weevil adult. As adults and larvae, this weevil feeds on numerous species of herbaceous and woody plants. |
Adult diaprepes root weevils. Adults and larvae feed on citrus and more than 270 species of plants in 59 plant families. |
Filbert weevil adult. The larvae feed in oak acorns and nuts of chestnut, hazelnut (filbert), and tanoak. |
Fuller rose beetle (weevil) adult. Hosts of adults and larvae include acacia, avocado, box elder, citrus, oak, photinia, Prunus, Pyrus, and Rhaphiolepis species and rose. |
Giant palm weevils include this adult red palm weevil. They feed on date palms, especially Canary Island date palms. |
Pepper weevil adult. Pepper weevils feed in buds and fruit of pepper and other plants in the Solanaceae family. |
Poplar and willow borer adult. As a larva, this weevil tunnels in and kills limbs of alder, birch, poplar, and willow. |
Rose curculio adult. Adults and larvae chew on rose blossoms and inside rose fruit (hips). |
Vegetable weevil adult. Adults and larvae feed on buds, foliage, and roots of potato, tomato, carrot, lettuce, and other vegetables. |
Life cycle
Weevils develop through four life stages: egg, larva, pupa, and adult. In some species both adults and larvae feed on above-ground plant parts. In other species, the larvae feed inside plant parts or in soil on roots while only adults feed above ground.
Note that some weevil species are beneficial because they feed on weedy plants, suppressing weed abundance. Beneficial weevils introduced for biological control of weeds include Bangasternus orientalis and Eustenopus villosus that feed as larvae in the seed heads of yellow starthistle, reducing the weed's subsequent abundance. Microlarinus lareynii and M. lypriformis feed inside seed heads or stems of puncturevine, reducing this thorny weed's reproduction and spread.
Solutions
See the text links above for the biology, identification, and management of particular groups or species of weevil.
Adapted from Pests of the Garden and Small Farm: A Grower's Guide to Using Less Pesticide and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).
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