We have now experienced 25 years of significant drought in the southwestern United States and northwestern Mexico. In the Colorado River basin (Figure 1), the annual flow of the Colorado River has decreased by approximately 19% in the 21st century compared to the 20th century.

From 1906 to 2000, the Colorado River basin averaged about 14.6 million acre-feet (MAF) annually. In the 21st century, average annual flows on the Colorado River have averaged approximately 12.5 MAF per year. This represents a decrease of about 1.75 MAF per year, which is approximately 19% less than the 20th-century average (https://www.congress.gov/crs-product/R45546).

This decline is attributed to the change in the climate with warming temperatures and reduced precipitation and is being referred to as a megadrought. The megadrought in the southwestern United States, beginning in 2000, is currently the driest multi-decade period in the region since at least 800 CE. This megadrought has been the driest in at least 1,200 years, exceeding a similar megadrought in the late 1500s. (Woodhouse, et al. 2010).

Long range climate models predict further reductions in Colorado River stream flows, with some projections showing declines of 5% to 30% compared to the 1971-2000 average by 2050 (Colorado Climate Center, 2023).

As a result, reservoirs are low throughout the region and the stress on water delivery systems is extreme. Recent projections by the U.S. Bureau of Reclamation indicate a high probability of water levels at Lake Mead in December 2026 to be lower than 1,050 ft. above sea level (Figure 2), which would trigger Tier 2a reductions based on the 2007 interim guidelines, Minute 323, lower basin drought contingency plan, and the binational water scarcity contingency plan (Figure 3).

However, all these conservation guidelines on the Colorado River will expire in 2026. Therefore, there is still the need for the delegations representing the Colorado River basin states to develop an agreement on a new set of conservation guidelines. At present, the lower basin states are in agreement, but the upper basin states will not accept the terms proposed by the lower basin states. Thus, they remain at an impasse.

Based on the Law of the River (The Law of the River: Foundational Documents and Programs, CRS, 2025), if the basin states are not able to decide on a new plan together, the U.S. Department of the Interior (DoI) and the Bureau of Reclamation (BoR) will have the responsibility for making the decisions.

At present, a new commissioner for the BoR has not been appointed by the new federal administration. However, based on my understanding from recent basin state meetings, the BoR has been more engaged under the Trump administration and that should be helpful. Stong leadership on these issues is urgently needed, and the situation is presenting a serious test on our system of governance on the Colorado River.

Figure 1. The Colorado River basin and U.S. areas that import Colorado River water.
Source: Bureau of Reclamation, Colorado River Basin Water Supply and Demand Study,
2012.


Figure 2. Lake Mead end-of-month elevations based on model projections from April and
May 2025, 24-Month study inflow scenarios.


Figure 3. Tier 2a reductions based on the 2007 interim guidelines, Minute 323, lower
basin drought contingency plan, and binational water scarcity contingency plan.
Source: U.S. Bureau of Reclamation.

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Meerkat’ was seeded, then sprinkler-irrigated to germinate seed Jan 13, 2025 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂ backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.

Downy mildew (caused by Peronospora farinosa f. sp. spinaciae)was first observed in plots on Mar 5 and final reading was taken on March 6 and March 7, 2025. Spray date for each treatments are listed in excel file with the results.

Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft²areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft²area of bed was approximately 144. The percentage were then changed to 1-10scale, with 1 being 10% infection and 10 being 100% infection.

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided most effective control against the disease include Orondis ultra, Zampro, Stargus, Cevya, Eject .Please see table for other treatments with significant disease suppression/control.  No phytotoxicity was observed in any of the treatments in this trial.

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.)

Dr. John Palumbo never sought the spotlight, but everything he did—every trial, field visit, and conversation—pointed us toward something better: better science, better decisions, better farming.

I’ve looked up to John since my undergraduate days. He was the model of what I hoped to become: a scientist grounded in integrity, driven by purpose, and deeply connected to the people and land he served. A career-long dream came true when I asked him to join my Ph.D. committee—and he said yes. A defining moment in my journey that I’ll always carry with me.

The work we hoped to do with him is now a reminder of how much he still had to offer. But more than anything, I’m grateful. Grateful that I got to learn from him, talk with him, and be challenged by him. I especially loved when I’d share an idea and he would provide feedback like, “Now I don’t like the sound of that, and I’ll tell you why...” To me that meant he was listening closely. He cared. He was genuine.

John didn’t just give us answers—he gave us perspective and the confidence to ask better questions. His perspective came from a place of hard-earned wisdom which he shared humbly and freely. We’ve lost a giant, but his impact remains in our work, our conversations, and the values he quietly instilled. His presence is deeply missed—and deeply lasting.


-Macey Keith, Assistant in Extension

I had the privilege of knowing John for just over a year, yet his impact on my professional journey has been profound. To me, John was more than a colleague—he was a mentor. The knowledge I acquired from him will shape my career for years to come. His legacy was truly contagious and has inspired me to follow in his footsteps. John’s influence will continue to guide and motivate me throughout my life.

May God bless your soul, John. Rest in peace.

Lettuce is one of the most important vegetable crops in the Yuma, Arizona region. However, growing healthy lettuce in the desert isn’t easy. High temperatures, salty soils, and very low rainfall (less than 3 inches per year) make crop management especially difficult. Growers are always looking for better tools to improve crop growth while saving water and reducing input costs.

Biostimulants are one such tool. These are natural products often made from seaweed extracts, organic acids, or beneficial microbes that are added to the soil or irrigation water. They don’t replace fertilizers, but they can help plants grow better by improving how roots absorb nutrients and handle stress like heat, drought, or poor soil quality.

Our Trial in Yuma, AZ
To better understand whether biostimulants can help desert lettuce crops, we conducted a field trial during the 2024–2025 growing season at the University of Arizona’s Valley
Research Center in Yuma. The field was managed using subsurface drip irrigation, a water-saving system that delivers moisture directly to the plant roots below the soil surface. We tested a commercially available biostimulant made from organic compounds and micronutrients known to support root and shoot growth.

The trial included several treatments, some with biostimulant and some without, under both traditional and sensor-based irrigation scheduling. We tracked plant height every two weeks to monitor lettuce growth and compared results between the treated and untreated plots.

What We Found
In the organic lettuce trial, biostimulant use did not result in a clear or measurable increase in plant height. All treatments (Figure 1), whether biostimulant was applied or not, showed similar growth patterns and reached comparable final heights by the end of the season. In the conventional lettuce trial, the tallest plants appeared in the biostimulant-treated plots; however, the difference compared to untreated plots was small and not statistically significant. When the data from both systems were combined, conventional treatments consistently produced taller plants than organic ones, regardless of biostimulant application. These findings suggest that biostimulant effects on plant height are minimal and highly dependent on the production system and environmental or management factors.

Takeaway
Biostimulants may not be a magic solution for crop growth and development, but they offer promise as part of an integrated crop management strategy. In desert systems where water is limited and soils can be harsh, even modest improvements in plant growth can help growers increase their productivity and resilience.

Figure 1. Distribution of plant height: (a) Organic Field; Organic sensor-based irrigation +
biostimulant (OSB), Organic traditional-based irrigation (OTI), Organic traditional-based
irrigation + biostimulant (OTB), and Organic sensor-based irrigation (OSI); (b)
Conventional Field; Conventional sensor-based irrigation + biostimulant (CSB),
Conventional traditional-based irrigation (CTI), Conventional traditional-based irrigation +
biostimulant (CTB), and Conventional sensor-based irrigation (CSI); (c) Pooled data for
Organic and Conventional Field treatments. Each data point represents the average of
10 readings collected in the field at the Valley Research Center, University of Arizona,
Yuma Agricultural Center, Yuma, Arizona.

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts down in all traps over the last month; about average for December.

Beet armyworm: Moth trap counts decreased in all areas in the last 2 weeks but appear to remain active in some areas, and average for this time of the year.

Cabbage looper: Moths increased in the past 2 weeks, and average for this time of the season.

Diamondback moth: Adults increased in several locations last, particularly in the Yuma Valley most traps.  Below average for December.

Whitefly: Adult movement remains low in all areas, consistent with previous years 

Thrips: Thrips adult movement continues to decline, overall activity below average for December.

Aphids: Winged aphids still actively moving but declined movement in the last 2 weeks. About average for December.

Leafminers: Adult activity down in most locations, below average for this time of season.