Hatching of alfalfa weevil has begun. Alfalfa weevil is an important pest of alfalfa which defoliates the plant. Newly hatch larva typically feed on the terminal leaves and the new leaves are skeletonized.

Maturing larvae will move down plant and feed between the leaf veins. The time it takes to reach the adult stage depends on weather but typically is around eight weeks.

To scout, collect 10 stems at five different locations and tap the stems into a white bucket. Larvae will be dislodged and allow for a average number to be calculated.

If an average of one or more larvae per stem is found in the 10-stem sample, then the economic threshold is reached, and control is justified. Infestations often first occur on warmer south facing slopes of fields.

Insecticides may be used for control with several options available. But be sure to apply when temperatures are above 60°F. as we have seen reduced control when applying control at lower temperatures.

For more information, contact Wayne Flanary, Field Specialist in Agronomy, University of Missouri Extension at 816-279-1691.