Description and life history
The black vine weevil is the largest and most common of several root weevils, including the strawberry root weevil and the rough strawberry root weevil to attack Idaho hop yards. Root weevils are beetles (Coleoptera) that belong to the snout beetle family (Curculionidae).

Adult weevils emerge from overwintering sites in soil from early May to mid-Jun. Adults begin feeding within 24 h after emergence, but do not lay eggs for another 25-30 days. Eggs are deposited on the soil surface, in soil crevices, and on leaves near the base of plants. Beetles continue to lay eggs until late September and October. On average, a single female will deposit about 10 eggs per day for about 30 days.


Larvae emerge from eggs in 12 to 20 days and begin feeding on the roots of hop plants. Larvae are white, legless grubs with tan to dark brown heads. Larvae continue to feed and mature throughout the fall. Although a few black vine weevils overwinter as adults, most overwinter in the soil as non-feeding late instar larvae that pupate in the spring. There are no male black vine weevils. Reproduction is accomplished through the production of viable eggs without fertilization (parthenogenesis). Adult weevils are incapable of flight and are active largely at night. (back to top)
Black vine weevil larvae and pupae

Damage to hop
Adult weevils feed on hop foliage but this feeding is not reported to cause economic loss. Economic losses can result from larvae feeding on the roots of hop plants. Root damage by larval feeding results in reduced nutrient uptake, water stress and reduced plant growth. Premature leaf drop and plant death have been associated with feeding damage caused by black vine weevil larvae. Premature leaf drop and plant death have been associated with feeding damage caused by black vine weevil larvae. Heavy infestations may require that individual hop plants or even whole hop fields be removed from production. (back to top)

Black Vine Weevil Management
Black vine weevil (and other root weevils when present) can be controlled by using insecticides targeted at adult weevils. Applications are made about three weeks after adult emergence before egg laying begins. Insecticides are more effective when applied at night when adult weevils are most active. No host-plant resistance to black vine weevil has been identified in hop. Little research has been conducted with respect to the identification of arthropod natural enemies of black vine weevil in hop. However, control by several parasitic nematodes has been demonstrated in field trials.

Chemical treatment options are listed in the Pacific Northwest Insect Control Handbook. Because this information changes frequently be sure to check the latest edition of this book, which is available from the University of Idaho Resources for Idaho web page. Be sure to read, understand, and follow label directions. Whenever possible use compounds that are less, or non-toxic to natural enemies in hop fields.