Herbicide evaluations for controlling Littleseed canarygrass (Phalaris minor Retz.) in wheat grown in the Sacramento Valley of California.

Jerry Schmierer and Jack Williams, Univ. of California Cooperative Extension;
Lorianne Fought, Bayer Corp.; Matt Ehlhardt, AgrEvo.

During the 1998-99 growing season, field trials were established at three locations in Colusa and Sutter Counties to evaluate the effectiveness of several potential herbicides for control of littleseed canarygrass, a common weed pest of wheat in the Sacramento Valley. The herbicides were tested at different rates and applications made at different stages of wheat/weed development. The earliest application was made when the wheat was in the 3-leaf stage and the canarygrass in the cotyledon stage. The last application was made when the wheat was fully tillered (approx. 12 inches tall) while the canarygrass was only 6 to11 inches tall with plants in all stages of development. Herbicides tested were Bayer MKH6561, Puma (fenoxaprop+mefenpyr), Horizon (clodinafop), Achieve (tralkoxydim), and the current standard, Hoelon (diclofop-methyl).

Each trial was laid out in a randomized complete block design. One trial (WHT98-1) had 3 replications and the others had 4 replications. Individual plots were 10 ft. by 25 ft. with a treated area in each plot of 6.67 ft. by 25 ft. This allowed for an untreated check area in each plot so that weed presence and density could be determined. All herbicide treatments were applied using a CO2 pressurized backpack sprayer. The application rate was 22 gallons per acre. This was accomplished by using four XR8002 flat fan nozzles spaced at 20-inch intervals on the spray boom and operated at 30 psi. Visual weed control evaluations were made using a 0 to 10 rating scale when the canarygrass and wheat were fully headed out. A 0 rating was no weed control, 10 was 100 % weed control and a rating of 8 was determined to be an economic control level that would be satisfactory to a commercial wheat grower. The canarygrass population of each plot treated area was estimated by counting heads in a 2-sq. ft. sample area that was repeated 3 times in each plot. The results of the sampled area were extrapolated to the approximate treated area (175-sq. ft.) and reported in the tables. Grain yield was measured by harvesting an area of 5 ft. by 25 ft. in the treated area of each plot using a small plot grain combine.

The results of these three trials indicate that Bayer MKH6561, Puma and Horizon gave greater than economic control of littleseed canarygrass at all of the rates tested and at all stages of growth that applications were made. It was surprising that such good canarygrass control was attained at the last application timing, when the wheat was 12 inches tall and overshadowed the 6-11 inch canarygrass. Achieve did not economically control canarygrass at any rate tested. Hoelon was only applied at an early 1-4 leaf canarygrass stage, and did satisfactorily control canarygrass at this timing.

The only significant yield increase from the herbicide treatments occurred in WHT98-3 where the canarygrass population was high enough to compete and lower wheat yields.

The MKH6561 treatments (Trt. Nos. 2&3, WHT98-1) at the 3-leaf no tillers stage of wheat growth stunted and yellowed the treated wheat. The wheat recovered and yield was not affected. No other wheat phytotoxicity was observed.

Data Tables:
WHT98-1
WHT98-2
WHT98-3