New alfalfa varieties are constantly being introduced into the marketplace. The number of varieties available for low-elevation desert areas in Arizona in the non-dormant and very non-dormant class is close to 50. New varieties are introduced each year and unbiased yield comparisons are helpful to the grower to base the decision of whether or not to sow a new variety. The study reported here is part of the on-going effort to evaluate alfalfa variety performance in Arizona. A summary of small grain variety trials conducted by the University of Arizona can be found online at http://ag.arizona.edu/pubs/crops/az1267.pdf.

Four rates of BAS125 were evaluated to document rate effects on reduction in stem elongation and associated increase in alfalfa leaves during the peak period of summer growth. Increasing rates of BAS125 resulted in greater inhibition of alfalfa stem elongation, as the highest rate (0.1875 lbs. a.i./acre) had stems 27-37% shorter than the untreated check through 12 days post treatment, and 20% shorter thereafter. Alfalfa weights (both stem and leaf) were also reduced by BAS125 treatments through 12 days after treatment. Higher rates resulted in lighter leaves. Significantly more trifoliate leaves were noted at the higher rates of BAS125 at 19 days after treatment, as was increased leaf and stem weights than untreated check with most noted at the 0.125 rate. Stem diameters were not significantly different, although untreated stems were wider. Numerically more open flowers were documented with usage of BAS125 at 19 days post treatment, but fewer floral racemes/stem were associated with higher rates at 27 days post treatment. No differences existed for alfalfa plant height measurements in regrowth following harvest, indicating that application of BAS125 are only effective on forage harvest to which they were applied and have no subsequent residual effect.

Thirteen alfalfa varieties with fall dormancy ratings of 7 - 9 were tested in a replicated small plot trial on a clay loam soil on the Safford Agricultural Center. This was the first year of the study. Beacon was the highest yielding variety in 2003 with ZX 9899B and AmeriStand 801S following closely behind. All three varieties produced a yield over 9 tons per acre.

Asset® RS, HydraHumeTM and SuperBio® Ag Blend were evaluated during several sequential alfalfa harvests for their effects on alfalfa yields and quality. Addition of Hydra-HumeTM or AgBlend when applied via chemigation appear to have slightly increased hay yields over the three cutting period by 0.12-0.22 tons/acre respectively when compared with an area of the field that received 10-34- 0 but was a different soil type. Addition of Asset® RS to Hydra-HumeTM did not provide any additional consistent yield increase in this study. Addition of Asset® RS resulted in increased hay quality as measured by protein levels, acid detergent fiber, total digestible nutrients, neutral detergent fiber and relative feed value. These parameters were often statistically different than the Hydra-HumeTM treatments. It is unknown if application of Asset® RS would result in similar or greater quality and yeild response alone or on another soil type. Different results for all products may occur if heavier soils are used for experimentation rather than sandy soils, as nutrient availability is affected by soil type and pH.

Two formulations of the insecticide active ingredient cyfluthrin (Baythroid® 2, Renounce® 20WP) were compared for fall alfalfa insect control, as was a lower active ingredient rate of both chemistries that included dimethoate. Differences in formulation effects of cyfluthrin were noted for cowpea aphids, spotted alfalfa aphids and alfalfa caterpillars at one day post treatment. At four days post treatment formulation significant differences were evident for numbers of bigeyed bugs, while at seven days after application formulations differed in numbers of spotted alfalfa aphids. Usage of dimethoate with a lower rate of cyfluthin resulted in less control of threecornered alfalfa hoppers throughout the study, improved initial control of spotted alfalfa aphids and clover leafhoppers, an increase in leafminer flies at four days post treatment and reductions in numbers of bigeyed bugs and spiders on this sample date, as well as significant reductions of lygus bugs later in the study compared with cyfluthrin only treatments.

Nine insecticides were applied on March 10, 2004, to alfalfa that had been water stressed prior to irrigation on March 6. These actions were thought to have resulted in treatments means with less distinct differences than usually noted for these treatments at 7-14 days post treatment. All pyrethroid treatments as well as Lorsban® and Steward® treatments resulted in significant reductions of alfalfa weevil larvae at four days post treatment. The Trilogy® treatment did not result in acceptable control of this pest. Significant increases in adult alfalfa weevils were noted at 10-14 days post treatment in pyrethroid treated alfalfa, perhaps due to increased production of certain plant volatiles in response to this class of insecticides. Low numbers of blue alfalfa aphids were noted in this study partially due to insecticide control as well as numerous beneficial insects. Fewest damsel bugs were noted from alfalfa treated with MustangMAXTM and Warrior® insecticides.

Trilogy® was applied via swather at cutting in April to alfalfa infested with twospotted spider mites. Data from samples obtained at 12 days after application noted somewhat reduced spider populations as a result of Trilogy® application, although new growth was thought to be re-infested from previously cut alfalfa which was in contact with new growth. Western flower thrips later became very prominent in plots and resulted in greatly reduced spider mite populations. Trilogy® treatment resulted in increased yields thought due to larger stem diameters as a result of fewer spider mites early in study. Very slight increases were also noted for alfalfa quality parameters as a result of Trilogy® application. Economic analysis indicated that Trilogy® applied via swather in this experiment resulted in a net increase in alfalfa valued at $2.12/acre.

Two formulations of Velpar® (DF, L) were evaluated over multiple alfalfa varieties to compare the potential phytotoxic effects this product. Treatments were made April 15, with yield and stem data collected on May 10. Both Velpar® formulations resulted in yellowed alfalfa within three days of application, with symptoms disappearing by 21 days post treatment. Yield data indicated increased yields from alfalfa treated with Velpar®, due to increased numbers of stems. The reason for the stem increase associated with Velpar® usage is unknown.

Five treatments were applied at time of bale removal to evaluate several products for twospotted spider mite (Tetranychus urticae) management in alfalfa hay. Mite numbers were very high prior to this harvest and were assumed to be more than adequately present for this study. Data were obtained at six, fifteen and eighteen days post treatment. Data at six days after application documented that only ZealTM and Trilogy7 had fewer spider mites than the untreated check, but data also indicated that western flower thrips (Frankliniella occidentalis) were also probably present and feeding on mites. Western flower thrips were present in almost equal numbers as twospotted spider mites at fifteen days post treatment and mite numbers had decreased greatly from the previous sampling date. Mite numbers/stem were similar at eighteen days to that of fifteen days post treatment. Thrips predation was thought to obscure differences in spider mite populations resulting from treatments in this experiment, and therefore data from this experiment should be so noted when future treatment decisions are considered.

Alfalfa was treated with five rates of BAS125 on August 5, 1997. Data were obtained to determine rate effects on stem regrowth (both height and width), trifoliate leaves, and yield. Variation in plot area affected some results. No statistical differences were noted for quality classification or yields, although increased protein levels were noted from BAS125 treatments. Increasing BAS125 rates resulted in significant decreases in plant height and significant increases in numbers of trifoliate leaves at nodes 1-6. Differences in stem diameters were also noted, with stem width affected by rate of BAS125 at lower portions of stem. Differences in stem diameters of upper parts of stems were primarily associated with plant height reductions as a function of BAS125 rate.