Summer weeds including established bermudagrass and nutsedge are of economic concern to alfalfa growers in western Arizona. Two replicated evaluations of norflurazon herbicide applications for summer weed control were conducted on established alfalfa fields in La Paz County. Zorial Rapid 80 WP and Evital 5G herbicides were tested for their effectiveness of bermudagrass and nutsedge control when applied following hay harvest but prior to irrigation in early spring. Zorial 80 WP was applied at 2.0 lb a. i. /acre. Evital 5G was applied at single application rates of 1.5, 2.0, and 3.0 lb a. i. /acre in spring and two split applications in spring and summer for a total of 2.0, 3.0, and 4.0 lb a. i. /acre. Norflurazon applications resulted in bleaching and shoot tip death of established bermudagrass 49 days after a single application (DAT), however by 78 DAT bermudagrass regrowth reinfested all plots resulting in zero control. Purple nutsedge control resulting from a single application of Evital 5G at 2.0 lb a.i./acre was 41, 82, and 35% at 35, 63, and 99 DAT, respectively. However, Zorial 80 WP applied at 2.0 lb a. i. /acre provided only 5, 23, and 0% purple nutsedge control at 35, 63, and 99 DAT, respectively. The limited effectiveness of the Zorial 80 WP spray solution for nutsedge control resulted from poor soil incorporation since the liquid was unable to penetrate the dense nutsedge foliage. The Evital 5G norflurazon formulation provided promising purple nutsedge control following one application to established alfalfa since the weight of the granules allowed the herbicide to reach the soil surface where irrigation could move the herbicide down through the soil profile to nutsedge roots. At 99 DAT a second split Evital treatment was applied to control nutsedge regrowth, and hopefully provide season long control. Nutsedge control results following this second split application are pending.

Plant growth regulators were aerially applied on April 26, 1996, to two alfalfa fields, one (Cibola) in its first year of production and the other field (CUF 101) in its third year. The first year field was approximately 50% through the cutting cycle and the third year field was approximately 30% through the cutting cycle when applications were made. No statistical differences were noted in hay tonnage the first cutting after application. Yield increases due to treatments were noted in the second cutting and maximum increases ranged from 277 -461 lbs of hay per acre. No yield or quality differences were noted the third cutting after application. The two fields differed in their response. The lowest rates of plant growth regulators produced higher yields in the first year field, but these treatment rates had greatly lowered hay quality the previous cutting. These effects were not noticed in the third year stand field. Increased hay tonnage was noted in the third year field from the 16 oz/acre rates, but was not evident in the first year field. Hay quality was usually highest in the check the first two cuttings after treatment. It is unknown if the differences noted between the two fields are due to different age of plants, variety and/or stage of growth when treatments were applied.

Some growers feel that nitrogen (N) fixing nodules found on the roots of the alfalfa plant are ineffective in cold soil during the winter and early spring. Thus, starter N fertilizer is commonly applied in late winter to established alfalfa to enhance growth until spring when the soil warms up and alfalfa begins actively fixing atmospheric N₂. Established alfalfa normally does not benefit from applications of N fertilizer since it is a leguminous crop that is capable of fixing its own N from atmospheric N₂. Afield experiment was conducted to determine the effect of N fertilizer applied in winter on alfalfa hay yield at the first cutting in spring. Two treatments consisted of an unfertilized check plot and UAN 32 water run at a rate of 35 lbs. N/acre to three year old 'CVF 101' alfalfa grown on a silt loam soil testing deficient in nitrate-N. Maximum alfalfa hay yield (J ton/acre) was obtained at the first spring cutting without N fertilizer application. However, since the field has a known yield potential of 1.5 ton/acre, factors other than fertility influenced the alfalfa hay yields observed in this study.

The combination of Spotlight* at 1.0 pt/A plus Speedzone* at 4.0 pt/A gave 90% control of khakiweed at 14 days after treatment (DAT) and continued to offer acceptable control of 85% at 49 DAT. Acceptable control of 87 and 90% control was also observed at 14 DAT when Spotlight* was combined with Powerzone* or Speedzone*, respectively. The combinations of Spotlight* with Powerzone* or Trimec* were similar by marginally controlling khakiweed up to 21 DAT. Spotlight when combined with Turflon Ester* or Speedzone Southern* performed very similarly at all rating dates and did not offer acceptable khakiweed control.

Two or three applications of Velocity at 30 g ai/A controlled P. annua 63 to 82% in two field experiments. Multiple applications of Velocity at 17 day intervals provided a higher degree of P. annua control compared to applications made at 28 day intervals. At approximately one month after initial applications, Velocity treatments, single or sequential, demonstrated 50 to 77% control of P. annua. The activity on P. annua was minimal at two weeks after initial applications of 30 to 60 g ai/A and slight chlorosis was evident. Perennial ryegrass exhibited chlorosis at two weeks after applications and appeared to recover at one month.

Seed head production from Poa annua is problematic on winter turfs, whether they are overseeded or not. Flowering culms are unsightly, prevent a uniform surface, and insure a continuous crop of seeds for the future. A field test was conducted to evaluate the effects of PROXY and a PROXY/PRIMO PGR tank mix for seed head control. Treatments were applied on three different dates in order to evaluate the degree of response of treatments and help define treatment window applications for future programs. PROXY when applied alone at 5 ounces/product/M produced a maximum of 60% seed head control at 26 days after a single application on February 15, and 83% seed head control at 27 days after a single application on March 1. A tank mix of PROXY/PRIMO (5.0/0.25 ounces/product/M) generally produced greater seed head control than PROXY alone. The tank mix produced seed head control effects quicker, greater, and longer than PROXY alone. Seed head suppression and percent seed head control was greatest when products were applied initially on either February 15 or March 1, 2001. PROXY/PRIMO produced the darkest color turf when applied on either February 15 or March 1. At least three tank mixes seem to be needed, applied monthly to suppress/control seed heads throughout the winter/spring season.

Post emergence applications of penoxsulam herbicide were generally ineffective in weed control of Khakiweed, (Alternanthera pungens). Moderate control was achieved by the high rate of granular Penoxsulam (0.052 G, 180-lbs. acre). This treatment had 28%, 34%, and 32% Khakiweed control on September 20, September 23 and September 29, respectively. Other rates resulted in minimal or negative control. The liquid SC formulation provided minimal control, at rates tested. Penoxsulam did discolor khakiweed, but did not cause enough injury to result in stand reduction. Further aspects for investigating Penoxsulam for control of this weed is presented.

The efficacy of six ALS herbicides for controlling purple nutsedge in bermudagrass turf was demonstrated in five field experiments during the summer of 2004. The highest degree of nutsedge control at 95% at the end of the summer was observed after three monthly applications of trifloxysulfuron at 0.026 lb a.i./A.. Three monthly applications of halosulfuron at 0.062 lb a.i./A controlled nutsedge 88 to 90% at the end of September to early October. Imazaquin at 0.5 lb a.i./A plus MSMA at 3.0 lb a.i./A gave 91% control of nutsedge with three applications. The most rapid and efficacious nutsedge control was observed with flazasulfuron giving 91% control at 15 days after a single application. The highest degree of nutsedge control with a single application of sulfosulfuron was 91 to 96% control at 28 days after treatment. In general, ALS herbicides applied as a single application or multiple applications provided one month of effective control following a first application. After one month, the degree of control declined unless repeated applications at monthly intervals or as needed were applied for extended control. Penoxsulam at 0.12 lb a.i./A in one test gave only 70% control. MSMA at 3.0 lb a.i./A was applied four times and nutsedge control at the end of the season was 63 to 66%.

Higher SU herbicide rates provided more effective ryegrass removal that resulted in improved establishment of the seeded bermudagrass. In most instances in this study, the percent bermudagrass coverage increased as herbicide rates increased. Glyphosate was very effective in completely removing ryegrass non-selectively. Flazasulfuron at 0.018 lb ai/A eliminated 88% of the ryegrass. Observations also showed that foramsulfuron, rimsulfuron,and chlorsulfuron were effective in removing ryegrass. In plots where ryegrass had been eliminated, faster bermudagrass coverage in a greater area of the plot was achieved. The least amount of bermudagrass coverage occurred in the untreated plots. It appeared that most of the herbicides evaluated in this study were relatively safe on seeded Princess 77 bermudagrass since emergence and establishment occurred in all plots. The speed and degree of coverage in the plots increased due to efficacy of the herbicides in eliminating ryegrass prior to seeding.

Velocity, (bis pyrobac-sodium) was applied at different ai/a rates in multiple application series to evaluate treatments for post emergence seed head and vegetative control of Poa annua var. annua. Velocity herbicide, when applied to perennial ryegrass overseed turf with heavy PA infestations, caused periodic discoloration of the ryegrass and yellowing/bronzing of the PA. The leaf yellowing of PA caused by Velocity is in contrast to color enhancement of PA from Proxy/Primo tank mixes. Seed head suppression of PA from Velocity was slightly greater in early April, than in early March. As cumulative treatment amounts of active ingredient of Velocity increased, the seed head suppression increased for treatments beyond the 30 + 30 gm ai/a rate. Above this rate, seed head suppression was increased, but not consistently with the applied active ingredient rate. Seed head suppression of PA on March 5 from Velocity ranged from 35% to 75% among Velocity treatments applied at 30, 45 and 60 grams ai/a. Embark alone had fair seed head suppression from early to mid-March, but decreased dramatically afterwards. There was no benefit of the 30 + 60 gm ai/a treatment, over the 60 + 60 gm ai/a treatment for seed head suppression of PA. Biological response in terms of absolute rate of ai/a applied and response to cumulative amounts of total Velocity were not consistent for PA seed head suppression or vegetative control. No product affectively reduced vegetative control of PA in a highly infested stand of PA which was 40-50% PA. If Velocity is to be competitive against other PA seed head reducing products, rate structures and timings may have to be amended for more multiple applications.