Selected Insecticide Performance against Egyptian Alfalfa Weevil Larvae

Alfalfa weevil overwinters as an adult in field trash or other secluded hiding places and

emerges in late winter or early spring. Soon after emergence and mating, the adult females begin inserting their eggs into the alfalfa stems, and hatching larvae make their way up the stem to feed on alfalfa terminals and drop to spin a cocoon and pupate by early summer. This species generally has only one generation a year. To sample for weevil larvae, divide the field into 4 or more sections and take 5 sweeps in each section. Divide the total number of weevil larvae by the total number of sweeps to get the field average. The treatment threshold is an average of 20 larvae per sweep. More information is available at the UC IPM Pest Management Guidelines for Alfalfa weevil here, http://www.ipm.ucdavis.edu/PMG/r1300511.html.

Larry Godfrey of UC Davis performed an insecticide efficacy trial against Egyptian alfalfa weevil (EAW) on the UC Davis Agronomy Farm.  Egyptian alfalfa weevil larval populations were measured in each plot with a standard 15-inch diameter insect net consisting of twenty 180^o sweeps.  Beneficial insects were also counted in the same twenty 180^o sweeps.  All materials tested performed well against EAW larvae.  Control with Lorsban 4E has been only moderate at this location for the last ~5 years, possibly due to resistance (although this has not been documented).  The pyrethroid products and Steward have consistently given good EAW control.  For the full article go here,  http://ceriverside.ucanr.edu/newsletters/Postings_from_the_Palo_Verde_Valley42159.pdf