California Root Borer

Pronunciation

How to pronounce Prionus californicus: /ˈpraɪənəs ˌkælɪˈfɔrnɪkəs/

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Summary

Prionus californicus, or California root borer, is a longhorn beetle species known for its larvae that damage deciduous trees and crops by tunneling through roots. Adults live for about 10-20 days and emerge from the soil mainly in summer.

Physical Characteristics

Adults: Robust, reddish-brown to almost black; three sharp spines on each side of pronotum; saw-toothed antennae with 12 segments. Males have distinctly sawlike antennae, more than 2/3 length of body. Females have more slender antennae, about 1/2 length of body. Larvae: Up to 80mm long, cream to brown in color, and strongly segmented.

Identification Tips

Males are smaller than females and have more strongly serrated antennae. The adults emerge from soil from June to early August and fly at night to mate, with males being more active.

Habitat

Primarily found in the roots of deciduous trees, shrubs, and some conifers. Also found in agricultural crops such as hops and grape vines.

Distribution

Western North America from Alaska to Mexico.

Diet

Larvae feed primarily on living deciduous trees (oaks, madrone, cottonwood) and are also recorded from roots of vines, grasses, and decomposing hardwoods and conifers; they will also attack fruit trees.

Life Cycle

The entire life cycle may require 3 to 5 years. Females lay 200 eggs, which hatch into larvae that feed on roots; pupation occurs near the soil surface.

Reproduction

Females lay cream to yellow-brown 4.8 mm long eggs, producing up to 200 eggs in her lifetime. Eggs are laid 1.25 to 3.8 cm below the soil surface near roots of suitable hosts.

Ecosystem Role

As a root feeder, larvae are important in nutrient cycling but can be harmful to host plants and tree health.

Economic Impact

Considered a pest of orchard crops, particularly fruit trees in the Intermountain West; can cause death of infested trees through girdling or by weakening host trees, making them susceptible to diseases.

Cultural Significance

Recognized as edible to humans in both larval and adult stages.

Tags

• California Root Borer
• Prionus californicus
• Insect
• Pest
• Coleoptera
• Cerambycidae