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.

Five different crops were evaluated in exploratory and observational field studies for potential use as a summer cover crop in a rotation with commonly grown vegetable and field crops. Sesbania ( Sesbania exaltata), cowpea (ViRna unguiculata), sunnhemp (Crotalaria iuncea var. Tropic Sun), sudangrass (Sorghum sudanense cv. Piper), and kenaf (Hibiscus cannabinus) were drill seeded and grown with 2-3 irrigations during the summer months in two field tests. In one test, fresh weight yields were: 7,794 lb/A for sesbania; 10,551 lb/A for sunnhemp; 5,184 lb/A for cowpea; 19,816 lb/A for sudangrass; and 2,390 lb/A for kenaf General observations indicated that adult whiteflies were attracted to sunnhemp at one test site but not at the other. Broccoli, cabbage, and barley were planted in the fall following the cover crops and general observations indicated that sudangrass significantly reduced all of the crops' stand and measurable responses were not evident where the other cover crops were planted.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Compared to current planting practices using naked lettuce seed, precision planting coated lettuce seed can result in substantially reduced thinning costs, increases in number of marketable lettuce heads per acre, and higher average head weight. The use of coated seed, however, requires more attention to seedbed preparation, planting depths, irrigation schedules, and stand maintenance. Hill - dropping naked seed does not appear to offer advantages over conventional planting practices except in a slight reduction of seed cost per acre.

Lettuce varieties were compared in Cochise County for late spring and early fall harvests. The Great Lakes 659 types consistently performed as well as any in the trials for these times of year in this area.

Preliminary tests have been initiated in a program for control of Sclerotiniose, or drop of lettuce. Damping-off problems are concurrently being investigated.

A number of chemical compounds have been field evaluated as potential pesticides for control of insects on lettuce over the past several years. The important pests of fall planted lettuce being the cabbage looper, beet armyworm and corn earworm. In addition to the chemical compounds, the disease organism Bacillus Thuringiensis was used. It is slower in acting, but can be quite effective, particularly against the cabbage looper. Some of the chemical compounds which have been evaluated and are now available commercially are Sevin, Dibrom and Bidrin. This evaluation will continue as new and possibly more effective materials are made available.