An experiment was conducted to ascertain the population level of Egyptian alfalfa weevil Hvpera brunneipennis (EAW) at which chemical control becomes economically justified. Four treatments were established by applying malathion at 1 lb. a.i./acre when an average of 5,10,15, or 20 weevil larvae were found per five sweeps; one treatment was sprayed every week (0 larvae) and the controls received no chemical treatment. Five 180- degree sweeps were taken weekly in each plot with a standard 15 -inch net and net contents were emptied into a white plate for counting. EAW larvae and adults were counted and insecticide was applied when the larval number reached the designated level. Hay from each plot was cut twice manually, air dried and weighed. Significant yield differences (P =0.05) occurred between the 0 larvae treatment and the other treatments for the first cutting but no yield differences occurred for the second cutting.

Alfalfa stem nematodes have become a more serious pest since the advent of non -dormant alfalfa. Their distribution has increased and their period of feeding activity has been prolonged. A state survey has been conducted to determine the presence of the nematode in the principal alfalfa- growing areas of the state. The population dynamics were followed during the 1985-86 growing season. Alfalfa samples, including stems and crowns, were taken from selected fields in each geographic area and the nematodes were extracted. Populations from the samples determined the fields infested and the periods of feeding and reproduction. More than one -half of the fields sampled in the Salt River Valley were infested with the nematode and new infestations were found in Yuma County. Warm weather from October through the winter permitted nematode activity, causing serious stand decline. This pest is becoming more widely distributed and more economically important to alfalfa growers in Arizona.

An alfalfa decline problem has appeared recently in fields between Poston and Parker in La Paz County. Cercospora summer black stem and leaf spot, a fungal disease of alfalfa, has been associated with the decline problem. The efficacy of three fungicides were tested for control of the disease and the decline problem. Bravo, Kocide, and Spotless significantly reduced the severity of Cercospora summer black stem and leaf spot; however, significant increases in yield were not realized. Alfalfa decline in La Paz County may involve other factors in addition to plant disease.

No description available.

The stem nematode Ditylenchus dipsaci attacks non-dormant Arizona alfalfa in the desert valleys; damage occurs during the cooler months of fall and spring. Efforts to introduce and retain resistant alfalfa has had limited success. From October until temperatures decrease below 50 F., the nematode reproduces and feeds. In warmer years, damage may be sustained from October until spring temperatures exceed 85 F. Chemical control may be warranted during these periods of feeding activity. Field trials were established to determine the efficacy of pesticides registered for use in alfalfa. Temil; Vydate, Furdan, Disyston, Thimet and Dasanit applied either in fall or spring were effective in controlling populations when first detected following dormancy. The best control is obtained when pesticides are applied immediately after harvest and prior to irrigation. Yield increases up to 15-25% were obtained with decreased yields in non -treated controls of 40-80%. Stand decline was reduced as much as 50% when treatments were correctly applied.