Sulfosulfuron showed the highest degree of nutsedge control after the first application among all of the treatments at 4 WAT. Nutsedge control began to decline at 6 WAT after a single application of sulfosulfuron. Halosulfuron, trifloxysulfuron, and penoxulam showed very good nutsedge control at 2 WAT after a second application was made. Trifloxysulfuron at 0.026 lb AI/A and penoxulam at 0.125 lb AI/A performed very similarly to halosulfuron at 0.047 and 0.062 lb AI/A. Halosulfuron and flazasulfuron were more effective at higher rates of application when a series of rates were compared. Halosulfuron at 0.047 and 0.062 lb AI/A were very similar at most rating dates and both rates gave acceptable nutsedge control of 86 to 88% control at the end of the season. The two highest rates of flazasulfuron at 0.023 and 0.047 lb AI/A gave almost acceptable control. Sulfentrazone was not effective in providing acceptable nutsedge control at the rate tested.

Speedzone at 4.0 pt/A provided rapid control of khakiweed and gave 82% control at 17 days after treatment in one of three experiments. Spotlight at 1.0 pt/A alone was only effective at about 50%. BAS-514 and BAS-790 were not effective against khakiweed when applied alone. In a second experiment, sequential applications of Speedzone and Spotlight plus Turflon Ester provided exceptional control of greater than 95%. Initial applications of the POST applications that were combined with Gallery offered control of new emerging seedlings of khakiweed. Monument combined with Gallery gave decreased khakiweed control compared to Monument applied alone. An antagonistic effect could be occurring with the tank-mix combination of the two herbicides. Carfentrazone containing products, QuickSilver at 2 oz/A alone was not effective on khakiweed compared to the package mix product Speedzone. For the ALS-inhibiting herbicides, flazasulfuron and Certainty were the least effective while penoxsulam and Image were comparable to Monument in providing about 50% control.

Italian ryegrass (Lolium perenne spp. multiflorum) is a common weed management problem in turfgrasses, cereals and non-crop areas in the United States. In Oregon, the number of populations with multiple-resistance continues to increase. To manage these resistant populations, the resistance patterns must be determined. In this study, five Italian ryegrass populations (CT, R1, R2, R3 and R4) from two cropping systems were studied for resistance patterns and mechanisms. The CT population is from a Christmas tree plantation and was resistant to at least six herbicides with four different mechanisms of action: atrazine, diuron (2.4-fold), glyphosate (7.4-fold), hexazinone (3.1-fold), imazapyr (1.8-fold), and sulfometuron. The resistant indices (RI) for sulfometuron and atrazine could not be calculated because 50% growth reduction for the CT population was not reached even with the highest rates applied, 17.6 kg ai ha⁻¹and 16 kg ai ha⁻¹, respectively, which are 16 times the recommended field application rates for this two herbicides. The CT population accumulated less shikimate than the S population. There were two mutations in the CT population, Trp591 to Leu in the ALS gene and Ser264 to Gly in the psbA gene, which explain the ALS and PII cross resistance, respectively. R1, R2, R3 and R4 were collected from annual cropping systems. All four populations were resistant to flufenacet. RIs for two populations, R2 and R4, were 8.4 and 5.9, respectively. R2 and R4 also were resistant to mesosulfuron-methyl, pinoxaden, quizalofop and clethodim. R4 was resistant to diuron, but R2 was not. An Asp-2078-Gly substitution in the ACCase gene was found in both R2 and R4 populations, while another Ile-2041-Asn substitution in the ACCase gene was found in the R4 population. These mutations explain the ACCase cross resistance in the R2 and R4 populations. The mechanisms for the glyphosate resistance in the CT population and the flufenacet resistance in R1, R2, R3 and R4 populations were not identified in this study. None of the five populations were resistant to the herbicide pyroxasulfone. / Graduation date: 2013