Introduction
Soil, water, and the climate of Arizona and the desert Southwest provide the basic natural resources necessary in the development and management of productive irrigated crop production systems. Understanding the soil resources in each field and the unique characteristics are important factors in maintaining soil health and sustainable crop production systems. Soil surveys have been developed for every county in the United States by the United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS). Soil surveys are provided in a consistent format and have been available for many years in hardcopy through local NRCS offices. They can now be accessed online and there are phone apps (i.e., SoilWeb) that are convenient methods of obtaining soil survey information for direct field observations.
Why Soil Surveys Matter in Irrigated Crop Production Systems
Important soil properties such as texture, depth, permeability, salinity, sodicity, and organic matter content are provided for each soil type (soil series) identified in the field. Soil surveys have been conducted and field maps provided on a scale of 1:20,000 in most cases. This provides a high level of detail in identifying soil types and natural field variability.
In my experiences working with agricultural areas across Arizona and the desert Southwest over the past 40 years, these USDA-NRCS soils are very accurate. They provide an extremely valuable resource for farm and field management. The soil survey maps can be helpful in developing irrigation systems, identifying possible internal soil drainage problems, recognizing water retention capacities of field soils, and evaluating crop variability patterns (Soil Survey Staff, 2017).
Managing Salinity and Soil Drainage
Salt accumulation is a natural consequence of irrigated desert agriculture primarily due to evapotranspiration greatly exceeding rainfall. Without proper leaching and drainage, soluble salts can accumulate, and salinity can limit crop yield and high sodium concentrations can impact soil structure. Soil survey data helps identify areas with shallow restrictive layers that can restrict internal drainage and leaching, natural saline zones, or naturally high sodium levels that require special management (Oster et al., 2012; Franzen et al., 2022).
Digital Tools
The development of the Web Soil Survey and Soil Data Access platforms provides easy access to integrate soil resource information with field implementation. Managing fields for optimal soil health begins with a good understanding of the soil types in each field and the natural variation among soil types across a field (Soil Survey Staff, 2022; USDA–NRCS, 2024).
Arizona soil surveys can be accessed through the following link to USDA-NRCS sites:
https://archive.org/details/usda-arizona?page=2
The Soil Survey of the Yuma-Wellton Area, Parts of Yuma County, Arizona, and Imperial County, California can be accessed through the following link, and pdf copies can be downloaded:
Conclusion
The USDA-NRCS soil surveys are valuable resources for management in irrigated desert agriculture. In the alluvial soils common across the crop production regions of Arizona, there is a high level of natural variability that is often not visible on the surface of the land. Management practices for optimum soil health and water conservation are optimized by understanding the nature of soil variability in a field and how the soil horizons are arranged in the vertical profile, particularly in the rooting zones of crop plants.
References
Franzen, D.W., D.L. Osmond, and J.J. Meisinger. 2022. Soil fertility and nutrient management in irrigated systems. In: J.L. Hatfield and T.J. Sauer, editors, Soil Management: Building a Stable Base for Agriculture, 3rd ed. ASA, CSSA, and SSSA, Madison, WI. p. 201–230. https://doi.org/10.2136/2018.soilmanagement.c11
Oster, J.D., I. Shainberg, and J. Rhoades. 2012. Salinity and sodicity management. In: R. Lal, editor, Encyclopedia of Soil Science, 2nd ed. CRC Press, Boca Raton, FL. p. 1571–1576.
Soil Survey Staff. 2014. Keys to Soil Taxonomy, 12th ed. USDA–Natural Resources Conservation Service, Washington, DC.
Soil Survey Staff. 2017. Soil Survey Manual, USDA Handbook 18. U.S. Government Publishing Office, Washington, DC.
Soil Survey Staff. 2022. Web Soil Survey. USDA–Natural Resources Conservation Service. Available at: https://websoilsurvey.nrcs.usda.gov
U.S. Department of Agriculture–Natural Resources Conservation Service (USDA–NRCS). 2024. National Soil Information System (NASIS) and Soil Data Access (SDA) User Guide. USDA–NRCS, Washington, DC.
Among the diseases affecting global date palm production, trunk rot caused by Thielaviopsis spp. stands out as one of the most destructive and cryptic. That it because this broadhost necrotrophic fungus wreaks havoc on the tissues of palms but often shows no foliar symptoms until the tree is ready to collapse and is firmly beyond saving. Thriving in both arid and semi-arid production systems, Thielaviopsis trunk rot (TTR), also known as black scorch when it attacks foliage and flowers, can be problematic in the date palm production regions of the southwest and of landscape palms across the broader United States.
TTR, also called Medjnoon or Fool’s disease, is primarily caused by two related species of fungi from the genus Thielaviopsis. These fungal pathogens can affect a wide range of palm species, including true date palms (Phoenix dactylifera), Canary Island date palms, and other ornamental palms commonly used in urban landscaping. The disease can affect all palm tissues, and the tissue affected is determined by where the spores opportunistically meet an open wound of the host and begin their infection.
Once inside the palm, the fungus secretes an impressively diverse array of plant cell degrading enzymes before parasitizing and eating the tissue it kills. In trunk infections, TTR often leaves behind nothing but the tough, lignified, fibrous vascular bundles (see Figure 1), severely compromising the structural integrity of the palm and causing it to become crooked, collapsed, or to break off entirely often with little warning. Consequently, this can be extremely hazardous to any objects, equipment, or persons unlucky enough to be below the tree at the moment of collapse.
Figure 1: The trunk of a collapsed date palm. Only the thin, flexible fibrous bundles
remain, while other stabilizing trunk tissue has degraded to the point of snapping under
the weight of its own canopy.
In Arizona, there are no pesticides registered for use in edible-date palm production that show curative action once an infection is established. That makes preventative measures the primary choice when managing this disease. Because wounds are necessary for trunk infections, take note of potential sources of injury and where they arise. Trunk cracking due to excess water uptake, insect feeding damage, bird pecking, debris from windstorms, and mechanical damage from human activity are a few of the many sources of injuries associated with Thielaviopsis infection. Injury should be minimized, especially when other stressors are present with the host. Intentional wounds can be treated with copper solutions to deter the successful germination of the pathogens spores, but ensure the copper is present before the spores arrive and for the duration that the wound is fresh and not yet corked over.
Spores of these fungi survive both as resting structures in the soil and on dead palm debris. Spores can be moved from infected trees or residues to healthy trees by wind and rain splashing as well as pests moving from tree to tree. Infected trees should be removed as soon as possible after infection is confirmed, and infected remains should not be composted or recycled as mulches. Spores can also be moved mechanically on contaminated implements shared between trees. This makes the disinfection of tools and spikes vitally important to minimizing spread from infected trees to healthy trees.
If you have any concerns regarding the health of your plants/crops please consider submitting samples to the Yuma Plant Health Clinic for diagnostic service or booking a field visit with me:
Christopher Detranaltes, Ph.D.
Cooperative Extension – Yuma County
Email: cdetranaltes@arizona.edu
Cell: 602-689-7328
6425 W 8th St Yuma, Arizona 85364 – Room 109
Finger weeders are an in-row weeding tool made from flexible rubber. Pairs are centered on the seed row and overlapped slightly to remove in-row weeds. Our experience has been that finger weeders are effective at removing small weeds (< 3-4 leaf stage), but not large, well anchored weeds. A Texas A&M University colleague shared that they were able to regularly remove 3-4inch tall Palmer Amaranth with finger weeders using a cultivator configuration developed by organic cotton grower Carl Pepper. I was pretty impressed by their video. I think you will be too. Check it out by here or by clicking on the image below.
Acknowledgements
Credit and thanks are extended to Kyle R. Russell, Texas A&M University, for capturing and sharing the video.
Fig. 1. Large Palmer Amaranth being removed from the plant row by finger weeders –
slow motion video. (Video credit: Kyle R. Russel, Texas A&M University. Cultivator
configuration credit: Carl Pepper, Lubbock, TX.)
Cantaloups & Specialty Melons, Late April-Early May
Spring-planted cantaloups and specialty melons are now seeded and established across Yuma. The first 3-5 weeks after planting are the most crucial period for weed management for the entire season. Weed escapes during this window often cannot be corrected once vines begin to run.
Weeds of Concern
Most of those weeds are just emerging and are easiest to control now. Once they exceed the 2-4 leaf stage, control becomes inconsistent and costly.
Critical Period for MelonsHerbicide – Based IPM Recommendations for Melons
Pre-Plant/Burndown (Before Seeding or Transplants)
Control all winter weed escapes before seed set, especially mallow and mustards
At or Just After Planting (Pre-emergence):
Apply at planting or immediately after, then activate with irrigation.
Broadleaf + Grass Control
Residual herbicides are essential during the first 3-4 weeks.
Early Post-emergence rescue (Before Vine Run)
Target weeds at the 1-3 leaf stage
Broadleaf
Grasses
Effective on small grasses; timing is critical. Late POST applications after vines run reduce control and increase crop injury risk.
Things to watch
Non-Chemical Options Worth Combining
The herbicide list for melons is very limited, but fortunately most melon types grown in the Yuma valley grow rapidly. Non-chemical weed control practices, including cultivation and plastic mulch, can be effective.
Takeaway Message
In Yuma melon production, the most practical program is usually a preplant burndown plus a residual pre-emergence herbicide, then a carefully timed postemergence rescue like Sandea or grass herbicide if needed. The exact choice depends on whether you are growing watermelon, cantaloupe, or honeydew, and whether you use plastic mulch, drip, or furrow irrigation.
Insect pests are constantly adapting to their environment. Over time, they have evolved ways to overcome control tactics. Repeated use of the same insecticides or tactics places strong selection pressure on pest populations. This allows the few individuals that can survive treatments to reproduce, leading to populations that are increasingly difficult to control, a process known as resistance.
Insects can develop resistance in several ways. Some break down insecticides more efficiently or develop changes at the target site that reduce product effectiveness. Others avoid exposure altogether by changing their feeding habits or movement patterns. In some cases, insects even develop thicker cuticles that reduce or slow down the absorption of insecticides.
Production practices can influence the rate of resistance development. Large, uniform cropping systems and repeated use of the same control tools reduce opportunities for susceptible insects to persist, accelerating resistance.
Figure 1: Chart illustrating how insecticide resistance develops when insecticides with the same mode of action (MoA) are used repeatedly.
What Should You Do to Mitigate Resistance in Insect Pests?
An integrated pest management (IPM) approach remains the best defense against resistance.
Key practices include:
No insecticide remains fully effective over the long-term if overused. Reducing selection pressure by avoiding consecutive applications of insecticides from the same IRAC group is critical. The more intensively a single tactic is used, the faster resistance will develop. Resistance can increase production costs, reduce marketable yield, and ultimately affect grower competitiveness. A diversified pest management approach helps preserve the effectiveness of available tools and supports long-term, sustainable pest control.
Additional Reading Materials
Water conservation is becoming increasingly important for desert growers as reduced snowpack, drought, and climate variability continue to pressure irrigation water supplies. To evaluate whether PolySorb could support irrigation water savings under desert conditions, we conducted a large-field evaluation using reduced irrigation levels with and without PolySorb.
The field study included three irrigation levels: 100% full irrigation treatment (FIT), 75% FIT, and 50% FIT. The 100% FIT treatment was used as the full-irrigation standard. PolySorb was evaluated under the reduced irrigation treatments, 75% FIT and 50% FIT, and was applied at a very low rate, approximately 2 inches below the soil surface (Fig. 1).
Figure 1. Field application of PolySorb in a desert crop production system at Yuma
Valley Farm Research Center at the University of Arizona.
The full irrigation treatment, 100% FIT without PolySorb, produced 17.5 tons/ac. When irrigation was reduced to 75% FIT without PolySorb, yield declined to 14.7 tons/ac. A stronger yield reduction occurred at 50% FIT without PolySorb, where the yield was 7.8 tons/ac. Adding PolySorb improved yield under reduced irrigation. The 75% FIT + PolySorb treatment produced 16.8 tons/ac, which was very close to the 17.5 tons/ac observed under 100% FIT without PolySorb. This represents only a 0.7 tons/ac difference, or about 4% lower yield, while using 25% less irrigation water. At the 50% irrigation level, 50% FIT + PolySorb produced 12.0 tons/ac, compared with 7.8 tons/ac with 50% FIT alone. This was an increase of 4.2 tons/ac, or about 54% higher yield than the same irrigation level without PolySorb (Fig. 2)
Figure 2. Fresh yield response to irrigation level and PolySorb application. Yield was
17.5 tons/ac under 100% FIT without PolySorb, 14.7 tons/ac under 75% FIT without
PolySorb, and 7.8 tons/ac under 50% FIT without PolySorb. Adding PolySorb increased
yield under reduced irrigation, producing 16.8 tons/ac at 75% FIT + PolySorb and 12.0
tons/ac at 50% FIT + PolySorb.
These results suggest that PolySorb may help improve irrigation efficiency under desert production conditions, especially at moderate deficit irrigation. The strongest response was observed at 75% FIT + PolySorb, where yield was comparable to full irrigation. PolySorb also improved yield at 50% FIT, although yield remained lower than the 75% FIT without PolySorb treatment.
From a practical grower perspective, PolySorb should not be viewed as a stand-alone solution to water scarcity. However, it may be a useful component of an integrated water-management strategy that includes irrigation scheduling, soil moisture monitoring, crop evapotranspiration information, and efficient irrigation delivery systems. More field testing across crops, soil types, irrigation systems, and seasons is needed, but these results indicate that PolySorb could be a promising approach to help conserve irrigation water in desert agriculture.
