- Author: Michael Rethwisch
- Editor: Ian M Grettenberger
This Grade Chart represents the average Insecticide Efficacy Grade against alfalfa weevil larvae from experiments conducted in the Palo Verde Valley over the past five years, with applications being approximately 18-20 gallons/acre to ensure excellent foliar coverage. Some products and rates are represented by only a single data point, while others have multiple year/rates of data. Data shown are from experiments which had weevil larvae numbers at or above economic threshold levels, providing high confidence in data.
Efficacy of pyrethroid insecticide products has changed through this period due to the development of insecticide resistance in this area's alfalfa weevils. Resistance has shifted multiple pyrethroids from highly effective tools to something that is no longer effective. This highlights the need for resistance management to maintain the materials that are still effective.