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.

Fifteen insecticide treatments were applied March 12, 2001, to compare their efficacies on alfalfa weevils, western flower thrips, blue alfalfa aphids and associated aphid predators. Furadan and insecticides containing a pyrethroid active ingredient reduced alfalfa weevil larvae by more than 89% when compared with the untreated check. All treatments provided a minimum of 70% control of blue alfalfa aphids by seven days post treatment, with fewest aphids noted in WarriorT insecticide treatments. Although some insecticides reduced adult western flower thrips number initially, adult thrips increased in all plots between four and seven days post treatment. Both treatments that contained Lorsban had significantly more adult thrips than the untreated check, indicating that low amounts of this insecticide may attract adult western flower thrips. At both four and seven days post treatment, nymphal thrips control was best in Success, followed by Furadan, dimethoate and treatments containing Lorsban. Higher numbers of thrips nymphs were noted in all pyrethroid treatments not in combination with other treatments than in the untreated check at four and seven days post treatment, perhaps indicating hormolygosis for western flower thrips and these insecticides. Few aphid predators were present until late in the study.

Twentynine insecticide treatments were applied on Feb. 7, 2002, to evaluate the effects of chemistry and rates on cowpea aphids and associated parasitic wasps. Data were also able to be collected on blue alfalfa aphids and alfalfa weevil larvae. At seven days post treatment fewest cowpea aphids were noted in plots treated with Furadan, the 3.84 oz./acre rate of WarriorT, and several of the higher rates of Lorsban 4E. Organophosphate insecticides had fewer cowpea aphids on the whole than did pyrethroid insecticides. All insecticide treatments had significantly fewer parasitic wasps than the untreated check, although these populations may correspond to aphid populations. All insecticide treatments had fewer blue alfalfa aphids early in the study, with very good control noted from the 3.84 oz./acre rate of WarriorT and the combination of 8 oz. of Lorsban 4E + 2 oz./acre of Baythroid 2. Treatments containing Baythroid 2 had the fewest blue alfalfa aphids at 44 days post treatment. Treatments which had at least 70% fewer weevils than the untreated check at 12 days post treatment included Furadan, all treatments that included any formulation of Baythroid, and the high rates of WarriorT and Pounce 3.2 EC, and the 0.088 rate of F1785 50DF.

Twenty six alfalfa varieties with fall dormancy ratings of 7 or 9 were tested in a replicated small plot trial on a sandy clay loam soil on the Safford Agricultural Center. This was the third year of the study. Coronado was the highest yielding variety in 2000 with Mecca III following closely behind. Both varieties produced a yield over 9 tons per acre and averaged 9.3 tons per acre over the 3-year period.

Three insecticide active ingredients (cyfluthrin, indoxacarb, and zetacypermethrin) were evaluated for their efficacy on several insects found in fall alfalfa in the low desert. Both liquid and wettable formulations were included for both cyfluthrin and zetacypermethrin, and four rates of indoxacarb were applied. Insect pressures were fairly low throughout the study. Pyrethroid chemistries (cyfluthrin, zetacypermethrin) provided excellent control of threecornered alfalfa hoppers for seven days after application while cyfluthrin applications resulted in lowest numbers of pale striped flea beetles during the same time period. All chemistries resulted in excellent control of the South American bean thrips (Caliothrips phaseoli). Indoxacarb treatments resulted in significantly increased levels of spotted alfalfa aphid, thought due to a reduction of big eye bugs noted with usage of this chemistry. Wettable formulations of both cyfluthrin and zetacypermethrin resulted in significant hay yield increases (0.1 tons/acre) when compared with their liquid formulations. An inverse yield trend was noted with indoxacarb rate. Usage of the liquid cyfluthrin chemistry also resulted in an unexplained quality decrease in this experiment.

Three miticide treatments (milbemectin, clarified neem oil, and chlorpyrifos plus dimethoate) were compared with an untreated check to obtain information on the effects of twospotted spider mite (Tetranychus urticae) feeding on alfalfa yields, quality and economics, as well as crop responses to miticides. Mite infested alfalfa was treated just prior to first irrigation after cutting in spring 2003, and numbers of spider mites and western flower thrips (Frankliniella occidentalis) were obtained at weekly intervals thereafter for the next seven weeks. Data for plant parameters (stem widths, numbers of leaves, internode lengths) were obtained at harvest, as were hay yields and quality. The milbemectin treatment resulted in quickest reduction of spider mites (88.5% at 5 days after application) and also resulted in significantly higher yields than the untreated check (0.18 tons of hay/acre), attributed to the longer internodes and resultant tallest plants and significantly thicker stems than the untreated check. Clarified neem oil and chlorpyrifos plus dimethoate treatments did not control spider mites as quickly as milbemectin and yields were increased by only 0.04-0.05 tons hay per acre in this experiment compared with the untreated check. These two treatments also differed in their effects on stem widths and internode lengths, indicating that some results noted were a result of interactions of miticides with alfalfa as well as spider mite control.

Twenty six alfalfa varieties with fall dormancy ratings of 8 or 9 were tested in a replicated small plot trial on a sandy clay loam soil on the Safford Agricultural Center. This was the first year of the study. Mecca III was the highest yielding variety in 1999 with Coronado following closely behind. Both varieties produced a yield close to 9.5 tons per acre.