Alfalfa Weevil Larval Control, Missouri, 1975

The test area was a new (fall) seeding of MFA’s WL-307 alfalfa. The soil Shelby loam with 5 to 10% slope and 4 to 8 inch surface soil. Results of soil tests conducted prior to seeding showed 4.6% organic matter and pH of 5.4. Effective neutralizing material (limestone) was applied to adjust pH to 6.1. One week prior to test application the field was sprayed with 3 qt 2,4-DB per acre to reduce a heavy accumulation of spring weeds. Sprays of the compounds under test were applied May 7 to 20 ft x 50 ft plots in a randomized complete block design with untreated checks in 4/replications. Spray treatments at the rate of 20 gallons per acre were applied at 40 psi with an IH cub tractor with a 20 ft spray boom and a power take-off roller pump. Eleven FS-6 nozzles with 50 mesh filter screens were spaced equidistance along the boom. Evaluation samples were taken May 14-15, 21-22, and 28-29. Primary sampling for efficacy against weevil larvae was by plucking individual stems of alfalfa from each plot and extracting the living larvae by heating in modified “Tulgren” funnels. Samples consisted of 25 stems per plot per sampling date. Labeled materials recommended for weevil control by the University were included in the test for standard of comparison. They were Furadan 4F 0.25 lb, Imidan 70WP 1.0 lb and en-capsulated me-parafhion (Penncap M 2EC) 0.5 lb A/A. The numbers of larvae recovered by stem pluck sampling at 7, 14, and 21 days post treatment are presented in Table 1.