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.

Five alfalfa varieties were planted and grown under grower conditions on a field section that had high conductivity, while two varieties were planted and grown on a section of the same field much less affected. CUF 101, the variety grown in both areas, was the highest yielding variety in both area. Reduction in CUF 101 hay yield due to high conductivity was approximately one ton/acre in the first year of production, with a large amount of this noted in the first cutting. Yield reductions of CUF 101 due to field area and associated electroconductivity were greater the second year, with an average of 0.29 tons/acre/cutting. Total yield difference for CUF 101 was 1.72 tons/acre for the eight harvests for which data were available. Yield differences between the areas was greatest in the early spring and late fall of the first harvest year, with differences not noted in the June cutting; in year two yield differences were approximately 37% for each cutting. Salado was the second highest yielding variety in the high electroconductivity area in 1998, and equaled CUF 101 in yield from this area in 1999. Sal-T-96 and Leivas Best yielded less than 90% of CUF 101. Sal-T-96 also had the greatest number of weeds, due in part to very slow germination and fewer plants per acre compared with other varieties.

Alfalfa yield and quality can be affected by the height and timing of cutting. This research was conducted to determine if 1) raising cutting height from 2 to 4 inches could increase stem density particularly during the summer months, and if 2) alfalfa cut at dusk and the following dawn differ in dry matter yield. Alfalfa was harvested from small plots eight times during the year in an experiment conducted at the Maricopa Agricultural Center in 1999 on a third year stand. The 4 inch cutting height resulted in consistently lower yields compared to the 2 inch cutting height even during the summer despite having slightly higher stem density. The 2 inch cutting height produced 12.5 tons/acre over the year compared to 9.9 tons/acre for the 4 inch cutting height. Forage yield was 3.7% higher for alfalfa cut at dusk compared to the following dawn. Alfalfa cut at dusk and weighed the following dawn lost a similar amount of dry weight overnight compared to alfalfa left standing. Any yield advantage of cutting at dusk can only be realized by greenchopping and immediately feeding the forage.

Many agricultural workers feel that 10-34-0 is a superior fertilizer for alfalfa since it is thought to move deeper in the soil with irrigation, be more available to the plant, and result in higher yields at equivalent rates compared to 11-52- 0. We found in our study with 24 cuttings over 3 years that alfalfa yields were similar if fertilized with 10-34-0 or 11-52-0 at equivalent rates. Total plant P was not affected by P fertilizer form or method of application. Broadcast 11- 52-0 resulted in higher soil P levels than water-run 10-34-0 and moved deeper in the soil profile. Broadcast 11-52-0 and water-run 10-34-0 appear to be equally effective P fertilizers for alfalfa in the irrigated southwest.

Twenty four alfalfa varieties with fall dormancy ratings of 8 or 9 were tested in a replicated small plot trial on a heavy clay loam soil on the Safford Agricultural Center. This was the fourth year of the study. WL 91-224F was the highest yielding variety in 1999, but that still left it in second place behind Cuf 101 for the four year average. WL 91-224F yield was 8.35 tons per acre which is very close to its four year average of 8.32 tons per acre. CUF 101 only had the heaviest yield in one out of the past four years, but its high 1998 yield gave it the highest average yield over the four years of the study, at 8.37 tons per acre per year. Heat units with thresholds of 77o F and 41o F are included for each cutting in the study.