Jun 28, 20232023 Insecticide Usage on Conventional and Organic Lettuce
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
Arizona agriculture utilizes ~ 70% of the water in this state and generates a strong and productive industry. Arizona agriculture generates more than $23B in sales as well as directly and indirectly supporting more than 138,000 Arizona jobs and employing more than 162,000 unique workers. Arizona ranks among leading states in the production of lettuce, spinach, broccoli, cauliflower, cantaloupe, honeydew melons, durum wheat, and other commodities. Arizona is an important area for the seed production of many crops that are used across the U.S. and worldwide. Many Arizona counties rank in the top 1% of all U.S. counties in terms of crop and livestock production (Murphree, 2018).
In response to the Colorado River (CR) water shortage and the current reductions in CR allocations to Arizona via the Central Arizona Project (CAP), which is primarily impacting agricultural irrigation districts in central Arizona, there is an increasing level of scrutiny on agricultural uses of Arizona water. This of course is accentuated with the recognition that agriculture utilizes ~ 70% of the Arizona water supply.
In the irrigation districts along the mainstem of the CR, there is a common adage of “First in use, first in right.” This is a fundamental aspect of the “law of the river”, which is an amalgam of the various laws, agreements, and rulings on the governance of CR water. Therefore, it is important for us to consider and prepare the positive case that can be made for the good stewardship of water resources provided by Arizona agriculture.
One common area of criticism that is directed towards Arizona crop production systems, is the use of surface and flood irrigation systems. The alternative irrigation methods that are commonly advocated for use instead of flood irrigation are methods such as drip irrigation, micro-irrigation systems, sprinklers, etc. Each of these are good irrigation methods and advantageous under the appropriate conditions. However, a good case can be made for the very efficient use of flood irrigation systems, particularly with high-flow turnouts and dead level (or very nearly so) basins for irrigation. When properly managed, these types of flood irrigation systems can be very efficient.
When we know the area to be irrigated, the flow rate of water in the irrigation delivery ditch, and the amount of water needed; then we can determine the proper time or duration for an irrigation event. If we can get fast and uniform coverage of the field to be irrigated, apply the proper volume of water to replenish the plant-available water supply to the soil, then cut off the flow of irrigation water into the field; we can do a very good job of delivery for high water-use efficiency.
To facilitate the process of managing individual irrigations for optimum efficiency, the Irrigator’s Equation can be used to estimate the depth of water applied or time (duration) of an irrigation event.
Q x t = d x A
Where: Q = the flow rate, in cubic feet per second (cfs);
t = the set time or total time of irrigation (hours);
d = the depth of water applied (inches) and
A = the area irrigated (acres).
With an understanding of the dominant soil type in the field being irrigated and the level of soil-water depletion at the time of irrigation, we can estimate the amount or depth of water needed to replenish the soil profile of plant-available water to support the crop and prevent water stress.
In managing crop fields and irrigations, we recognize that soil textures vary in terms of water holding capacities and it is important to understand the dominant soil textures in the field, not only on the surface but also through the depths of the soil profile through the effective rooting depth of the crop, Tables 1 & 2.
Collectively, we can manage surface or flood irrigation systems efficiently. In the crop production arena, it is important to communicate these points effectively.
Table 1. Soil texture and water holding capacity.
2. Depths to which the roots of mature crops will deplete the available water supply when grown in a deep permeable, well-drained soil under average conditions.
Source: Chapter 11, "Sprinkler Irrigation," Section 15, Natural Resources Conservation Service National Engineering Handbook
Murphree, J. 2018. Arizona Agriculture is 23 Billion Dollars Beautiful, Arizona Farm Bureau.
The soft-rot bacterium, Erwinia carotovora subsp. carotovora (syn.= Pectobacterium carotovorum subsp. carotovorum), enters through growth cracks or wounds caused by cold temperatures, insects, other disease organisms, or by mechanical means. Under warm, humid conditions, uninjured tissue may become infected through natural openings. Prolonged moisture from rain or irrigation and mild temperatures encourage disease development. Insects, tools, rain, clothing, or affected plant tissue can spread the bacteria. The bacteria survive in soil and plant debris.
Symptoms appear as small, water-soaked areas and enlarge rapidly. Tissue becomes soft and mushy, and within a few days the affected plant part may collapse. An offensive odor usually is present.
Vol. 13, Issue 3, Published 2/9/2022
Over the last couple of years, we have been investigated the use of band-steam to control weeds and soilborne pathogens. The technique has been discussed in previous UA Veg IPM articles (Vol. 12 (5), Vol. 11 (15). Briefly, the concept behind band-steam is to disinfest narrow bands of soil centered on the seedline using high temperature steam prior to planting.
Trials results have been impressive, particularly for in-row weed control (Fig. 1). We’ll be demonstrating our prototype band-steam applicator (Fig. 2) and sharing study results at the 2022 Southwest Ag Summit Field Demo, February 23rd. More information about the event can be found at: https://yumafreshveg.com/southwest-ag-summit/. I look forward to seeing everyone there.
If you are interested in trying band-steam on your farm, please let me know. We are in the process of constructing a second-generation band-steam applicator that has a higher capacity steam generator and simpler design than our first prototype and are seeking collaborators.
This work is partially funded by the Arizona Specialty Crop Block Grant Program.
Fig. 1. Weed control in seedline of beds treated with band-steam (center and left bed) and untreated (right).
Fig. 2. Band-steaming bed seedlines prior to planting in preparation for the 2022 Southwest Ag Summit Field Demo, February 23rd (https://yumafreshveg.com/southwest-ag-summit/).
Palafoxia arida is a plant from the family Asteraceae also called the Sunflower family. It is native to the Desert regions of California and the SW United States in AZ, NV, CA, UT, Baja California and Sonora. It is an annual weed that grows erect and has rough hairs on the leaves, which are grayish green and narrow or linear. This plant can grow up to 6 ft has a main tap root. The flower heads are about 2-3 cm long with several (up to 40) tubular five lobed florets white to light pink color. Its habitat includes sandy plains, mesas, washes, dunes.
We found this weed abundantly in our Yuma County Survey. The highest populations were found at the Yuma Mesa around fields. Also found in newly established alfalfa fields. Despite the fact that it prefers sandy soils we also detected Palafoxia all across the Yuma County from the Texas Hill area Wellton, Dome Valley to the San Luis Arizona border. Please see Yuma County map below.
The Arizona Vegetable IPM Team will be checking to see if this weed is a possible host for INSV (Inpatiens Necrotic Spot Virus).