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Pest Alert: Alfalfa weevils are emerging in North Dakota

May 26, 2016

NORTH DAKOTA: Adult alfalfa weevils have been spotted.

Alfalfa weevils are the primary defoliators of alfalfa. Eggs are laid in the alfalfa stems in the fall or spring by the adult female. When the eggs hatch, the larvae feed on the green plant tissue generally near the plant terminal early in the spring causing potentially fatal damage to alfalfa crops.

Growers are encouraged to be proactive when scouting before and after cutting. North Dakota State University offers these detailed descriptions of alfalfa weevils:


  • ¼ in. long and brown-golden
  • Blunt snout and dark brown longitudinal stripe in the center of the back
  • Antennae are elbowed and clubbed
  • Eggs are laid inside the stems of alfalfa, and are small and cream colored

Mature larvae:

  • ⅜ in. long
  • Black head capsule and a green-wrinkled body
  • A white stripe, running lengthwise, can be observed across the top

Peak feeding occurs in mid-June, so Syngenta recommends being proactive and utilizing an insecticide like Warrior II with Zeon Technology® to help ensure fast knockdown and long residual control of the most damaging insects, including alfalfa weevil.

Proper scouting and being timely with any treatment application is key to combating alfalfa weevils. Implementing these strategies can help maximize return on investment and grow more alfalfa.

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©2016 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. Warrior II with Zeon Technology is a Restricted Use Pesticide. Warrior II with Zeon Technology is highly toxic to bees exposed to direct treatment on blooming crops and weeds. Do not apply this product or allow it to drift onto blooming plants while bees are foraging adjacent to the treatment area. Warrior II with Zeon Technology® is a trademark of a Syngenta Group Company.