Three Steps to Control Alfalfa Weevil Damage

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Midwest alfalfa growers know that alfalfa weevil larvae can greatly impact their yields and the quality of their alfalfa plants’ nutrition. Alfalfa weevil larvae typically emerge in the spring. This yield-robbing pest can quickly “skeletonize” leaves and challenge regrowth for the next cutting. They feed on young alfalfa leaves, consuming the bulk of the plant’s crude protein, fiber, and carbohydrates, removing valuable nutrition from the forage.

To control alfalfa weevil larvae and protect your yields, consider following these three steps.

  1. Watch for alfalfa weevil larvae in your fields. Scouting your fields is essential to limiting damage from alfalfa weevil larvae. Consult with your crop advisor to develop an appropriate timeline and strategy for monitoring your fields for alfalfa weevil larvae damage. Alfalfa weevil larvae are lime green in color and have a white stripe down their back. Early signs of feeding appear as tiny pinholes in leaves but can progress to skeletonization in just three days.

  2. Cut alfalfa early to limit alfalfa weevil larvae damage. Cutting your alfalfa early can control alfalfa weevil larvae destruction, but it doesn’t eliminate it. This challenging pest can also damage some early second cutting regrowth.

  3. Consider using a crop protection product like Steward® EC insecticide from FMC. Work with your crop advisor to determine an appropriate economic threshold for spraying to control the alfalfa weevil larvae. Growers have limited options for insecticides that are labeled to control alfalfa weevil larvae. Steward EC insecticide is one option available to alfalfa growers. It acts fast to kill larvae with up to 14 days of residual control and has a short preharvest interval of seven days. Steward EC insecticide has a single active ingredient that fits well into integrated pest management (IPM) programs.

These three strategies can help you control yield-robbing pests and protect the valuable nutrition in your alfalfa crop.

The EPA label for Steward EC contains the following statements: This product is highly toxic to bees exposed to direct treatment on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are foraging the treatment area.

Always read and follow all label directions, precautions, and restrictions for use. Some products may not be registered for sale or use in all states. FMC, the FMC logo and Steward are trademarks of FMC Corporation or an affiliate. ©2023 FMC Corporation. All rights reserved.