HPIPM:Sunflower Root Weevil
Author: Frank B. Peairs[1]
Field Biology and Identification
Adult root weevils are black, oval‑shaped and about six millimeters (¼ inch) long. They have a short, almost blunt, downward projecting snout. Larvae are creamy white with a small brown head capsule and are about six millimeters (¼ inch) long at maturity. Adults appear in fields by June. They can be found feeding on sunflower foliage in early morning and late afternoon. Adults are often found around the root zone at the soil surface during mating. Bright yellow eggs are deposited two or three at a time in stalk tissue. Larvae can be found in stalks by mid‑July and by September and early October larvae form a "soil cocoon" around roots at a depth averaging two to five inches, where they overwinter.
Plant Response and Damage
Adults vector such fungal diseases as charcoal rot and Phoma black stem disease. Numerous larvae in the stalk will cause serious stalk breakage.
Management Approaches
Significant yield losses and stalk breakage have not been demonstrated with this insect. Insecticide treatments are not considered necessary under most conditions.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
