| Abstract/Contents: | "A preemergence study and a postemergence study conducted in 1992 are summarized below. Preemergence study. The preemergence herbicides in this study were applied at 75 gpa using a CO2-backpack sprayer equipped with a two nozzle boom. Plots were 3 by 10 feet and were arranged in a randomized complete block with three replications. The study site was core cultivated, grooved, and overseeded with locally harvested crabgrass (Digitaria spp.) in the fall of 1991. Excellent crabgrass pressure was present in all three replications and percent control was rated on August 21, 1992. The site was comprised of a mixture of Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and fine fescue (Festuca spp.). Most treatments were applied on May 7 or May 9 with the exception of bensulide which was applied at 7.5 lbs a.i./A on May 11. Not only was the bensulide rate too low, the timing was too near the date of germination (May 13); and as a result, control was not acceptable (greater than 85%). Prodiamine (0.65 lbs a.i./A), benefin (1.5 + 1.5 lbs a.i./A eight weeks later), benefin + trifluralin (3 lbs a.i./A and 1.5 + 1.5 lbs a.i./A eight weeks later), FN 9064 (250 and 375 lbs product A) pendimethalin (1.5 lbs a.i./A and 1.5 + 1.5 lbs a.i./A), dithylopyr (0.375 and 0.5 lbs a.i./A), dithiopyr + oxadiazon (0.125 + 2.0 lbs a.i./A), dithiopyr + oxadiazon (0.25 + 1.0 lbs a.i./A), dithiopyr + oxadiazon (0.25 + 2.0 lbs a.i./A), dithiopyr + oxadiazon (0.125 + 1.0 lbs a.i./A), MON-25134 (0.125, 0.187, 0.25, and 0.375 lbs a.i./A), EXP. 30742B (5 and 6 lbs a.i./A), EXP. 30925A (5 lbs a.i./A), benefin (2 lbs a.i./A), and DCPA (10.5 lbs a.i./A) all provided acceptable control. Injury was rated on June 30 and August 21. Fine fescue was the species in the mixture that was injured (stand loss or thinning). On June 30, benefin + trifluralin (Team) at 3.0 lbs a.i./A caused 25% fine fescue thinning and at 2.0 a.i./A caused 17% thinning. The Team split application at 1.5 followed by 1.5 eight weeks later caused less than 5% thinning. FN 9064 at 375 and 250 lbs product/A caused 35 and 15% thinning, repectively. The only other compound that caused 10% or greater thinning was oxadiazon at 4 lbs a.i./A. By August 21, only fine fescue that had been treated with the high rate FN 9064 had not completely recovered. Postemergence study. The post or combination pre/post herbicides in this study were applied at 40 gpa using a CO₂-backpack sprayer equipped with a two nozzle boom. Treatments were applied on July 14 when most crabgrass plants were approximately four leaf stage with some beginning to tiller. The site was comprised of the same species and crabgrass introduced into the site in the same manner as in the preemergence study. Dithiopyr at 0.38 and 0.5 lbs a.i./A, fenoxaprop at 0.25 lbs a.i./A, HOE-360-18H at 0.09 lbs a.i./A, HOE 360-08H at 0.09, 0.12, and 0.18 lbs a.i./A, MSMA at 2.0 lbs a.i./A followed by 2.0 lbs a.i./A two weeks later, the combination of dithiopyr and fenoxaprop at 0.38 and 0.18 lbs a.i./A, respectfully, prodiamine plus fenoxaprop at 0.5 and 0.18, respectfully, prodiamine plus MSMA at 0.5 and 2.0 lbs a.i./A, respectfully, benefin plus fenoxaprop at 2.0 and 0.18 lbs a.i./A, respectuflly, pendimethalin plus fenoxaprop at 1.5 and 0.18 lbs a.i./A, respectfully, and prodiamine plus quinclorac at 0.5 and 0.75 lbs a.i./A, respectfully controlled crabgrass better than 85%. Only fenoxaprop at 0.12 and 0.18 lbs a.i./A, HOE 360-08H at 0.06 lbs a.i./A, and quinclorac at 0.75 lbs a.i./A did not control crabgrass 85% or greater, although quinclorac and fenoxaprop did provide 78 and 83% control, respectfully. The only injury observed was caused by the two week repeat application of MSMA. The injury was a slight but temporary discoloration." |
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