An experiment was conducted during 1992-93 at the University of Ariwna Maricopa Agricultural Center to investigate the effects of nitrogen (N) and water management on yield, midrib nitrate-N, and N and water use efficiency of subsurface trickle-irrigated leaf lettuce, collard, and spinach. The experiment was a randomized complete block factorial with three water levels (deficient, optimum, excessive), four N fertilizer levels (deficient, suboptimal, supraoptimal, excessive) and four replications. Trickle tubing was placed in the center of the beds at 15 cm depth. Irrigation was applied daily as needed to maintain the appropriate target soil water tension and N fertilizer (urea ammonium nitrate solution) was applied in 4 to 5 split applications. Midrib samples were collected for nitrate -N analysis at 4 growth stages, and portions of the plots were harvested when plants were marketable size. The 1992-93 growing season was excessively wet, therefore optimum yields were achieved in the deficient irrigation treatment. The wet conditions apparently led to excessive N losses, therefore high rates of N fertilizer were needed for optimum yields. Nitrogen and water use efficiencies were maximized at low rates of water and fertilizer input. Midrib nitrate-N concentrations were responsive to N fertilizer treatments.

A beet armyworm population was collected from spinach in Yuma, Feb 1996. This population was evaluated for resistance to Lannate. A range of Lannate dosages were prepared by disolving Lannate into acetone. A miroapplicator was used to topically apply the dosages. Dosage-mortality data were obtained from 3rd instar larvae held for 24 hr after treatment. The BAW population tested in 1996 had an LD₅₀ of value of433.34 μg-methomyl/g -worm, compared to a historical susceptible strain which had an LD₅₀ of 17.54 μg/g-worm, a 24.7 fold increase in resistance.

In 1995 we initiated a resistance management program aimed at sustaining the efficacy of Admire®. This paper delineates the groundwork for the program, and describes methodological and conceptual advances toward our goal. Bioassay methods developed for adult whitefly consisted of a 1 day hydroponic uptake procedure using cotton seedlings. A reliable mortality criterion was also established. Results from a statewide survey suggested slight geographic variation in whitefly susceptibility to Admire®. Future studies will 1) continue to monitor susceptibility throughout Arizona, 2) evaluate the risk of resistance to whitefly populations in commercial greenhouses, and relate this to field populations, and 3) characterize the development of resistance in relation to cropping systems and spatial dynamics of whitefly. The overall objective of these investigations is to determine if a sustainable use strategy can be identified for Admire®.

The abrupt and widespread introduction and establishment of the B type whitefly B. tabaci (Genn.) (also B. argentifollii) in Arizona in approximately 1987-1990 has given rise to unprecedented losses in vegetable and fiber crops in Arizona, and elsewhere throughout the sunbelt states. This report documents the discovery and the tracking of B type whitefly over time in Arizona crop and weed species, and reports important biological characteristics of the A and B whitefly populations with respect to host range, host preferences, and virus-vector capabilities. Here, from tracking data, we provide direct evidence that the A and B whitefly populations existed simultaneously in the state for a short period of time during 1989-90, and that by 1991, the B type population had become predominant whitefly pest and whitefly vector of plant viruses in Arizona crops. Unique host ranges and host preferences represent the most important distinctions between these two populations of B. tabaci, and are largely responsible for the altered epidemiologies of several whitefly- associated virus diseases, and for new pest problems in previously unaffected crops. From these collective data, it is possible to present an historical documentation of the emerging importance of the B whitefly as a pest and virus vector in Arizona. An unusually broad host range and the ability to induce phytotoxic disorders, set the B population apart from the historically problematic, local A type B. tabaci, and provide insights into the underlying basis of its unprecedented impact on crop production in Arizona. Baseline information about whitefly biology, host range, and virus-vector capabilities is relevant to the design and implementation of management practices aimed at controlling the whitefly as a pest and virus vector in Arizona crops.

The Arizona Crop Information Site (ACIS) http://cals.arizona.edu/crops was launched by the University of Arizona in 2001. This site provides a one-stop resource for those seeking information on Arizona crop protection and production information. The site is the result of input and cooperation across Arizona’s agricultural community. The amount of information on the site continues to grow as does the site’s importance, usefulness and number of visitors.

Nitrogen transfer from aquaculture to agriculture in integrated systems has been difficult to quantify, and the contribution of fish effluent to nitrogen utilization by crop plants is poorly documented. Therefore, labeled nitrogen, ¹⁵N, was used in a small scale integrated system in a controlled environment greenhouse to determine nitrogen transfer from the fish system and its utilization by plants. Tilapia fish were grown in m³ tanks and fed a complete diet that was amended with ¹⁵N ammonium sulfate. Fish effluent amended with ingredients of a basic nutrient solution and 0%, 25%, 50% and 100% of the recommended mineral nitrogen was used to irrigate Summer Bibb lettuce in 5 gal lysimeters in two trials. In trial 1, percent ¹⁵N recovered by lettuce was significantly higher in effluent amended with 50% mineral nitrogen as opposed to 0% or 100%. Dry weight of lettuce was significantly lower only when irrigated with effluent only (no mineral nitrogen added). In trial 2, percent ¹⁵N recovered by lettuce was significantly higher in effluent amended with 25% mineral nitrogen as opposed to 0% or 50%. In treatments with the same amount of mineral nitrogen added, addition of effluent did not affect dry weight. Although ¹⁵N recovery demonstrated efficient nitrogen transfer from the fish feed to the plants, results indicate that effluent alone does not supply sufficient nitrogen for lettuce production.

Several laboratory studies were conducted to examine the relationships between larval developmental and foliage consumption. Neonate lepidopterous larvae were placed in controlled environment growth chambers to measure the time required to complete larval growth, and comparative foliage consumption at constant temperatures. Differences in developmental times and degree day estimates between beet armyworm and cabbage looper varied significantly with temperatures and host plant. In general, cabbage looper feeding on lettuce completed larval development at a more rapid rate and consumed more foliage than any other species-host combination. In one study, the time required to complete larval development between CL and BAW varied less than one day, but the difference in foliage consumed between the two hosts varied almost 40%. Results from these studies may provide information important for understanding the damage potential of lepidopterous larvae and optimizing use patterns for new compounds that will be integrated into management programs for leafy vegetables.

An experiment was conducted to examine the effectiveness of knifing a vshaped notch into the center of raised onion beds for reducing soluble salt accumulation in the seed rows. Sodium salts accumulated within an 18 inch wide band in the top six inches of the knifed raised bed profile. Sodium salts accumulated primarily within a narrow six inch wide band, and to a somewhat lesser extent, within an 18 inch wide band in the top six inches of the conventional raised bed profile. Total soluble salts accumulated primarily within a six inch wide band in the top six inches of the knifed and conventional onion raised bed profiles.

Pepper -- Arizona

The world supply of quality water for irrigation of crops is being depleted. Growers in the arid and semi-arid regions of the world, where irrigation is a requirement for crop production, are looking for ways to conserve their water use and increase their irrigation efficiency. One tool that has been useful in helping growers reduce their irrigation water inputs is computerized irrigation scheduling programs. This study is part of a joint project between the government of Egypt (National Agricultural Research Project), USA1D and The University of Arizona. Working together, researchers from Egypt and Arizona are developing water management tools that will help both countries better use their scarce water resources in arid environments. The main thrust of this segment of the project is to develop water use data on vegetables grown in both regions. These data will then be used to develop crop coefficient data to be used in AZSCHED, a computerized irrigation scheduling program developed at the University of Arizona. Using a subsurface drip irrigation (SDI) system, carrots, cauliflower, head lettuce, and tomatoes were grown to determine water use patterns and develop basal crop coefficients. Water use data were collected using a neutron moisture gauge and a time domain reflectometer (TDR). Soil water data were collected 1 day following an irrigation and just prior to the next irrigation. Additionally, three different watering regimens were employed using available water content in the rootzone as a trigger to initiate irrigation (20 %, 30% and 40% depletion). The carrots, cauliflower and lettuce were planted in early October, 1993, using a randomized block design. Yield data showed no significant differences between treatments for any of the vegetables. Also, the soil moisture data did not indicate water stress in the treatments. In March of 1994, tomato transplants were planted and the irrigation treatments were altered to 30 %, 40% and 50% depletion, in an attempt to get significant differences between treatments. The results for all four vegetables showed high variability in soil water data between replications, although an initial determination of basal crop coefficients was possible. Additional data will be required to better refine the crop coefficients.