In 2026 the 2007 Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for both Lake Powell and Lake Mead are set to expire. The seven Colorado River Basin states and stakeholders must work together to develop the new criteria that will replace those guidelines. At present, there is a gridlock in those negotiations between the Upper and Lower Basin states and it must be resolved in 2025 to replace those guidelines expiring in 2026.

As part of the 2025 SW Ag Summit program that was conducted on Thursday, 20 February on the campus of Arizona Western College, two sessions, the morning keynote and a morning breakout session, addressed the future of the Colorado River and the next set of management plans for water allocations that will be very important for agriculture in the lower Colorado River Valley in the next decade.

We were very fortunate to have in both sessions Mr. Tom Buschatzke, Director for the Arizona Department of Water Resources, and Mr. J.B. Hamby, Commissioner for the Colorado River Board for the State of California. Mr. Bushatzke and Mr. Hamby both serve as the lead negotiators for the delegations representing Arizona and California in basin-wide negotiations on the development of the new operational guidelines for the management of the Colorado River.

In the breakout session, Mr. Bushatzke and Mr. Hamby were joined by Mr. Hank Auza, President of the Yuma County Water Users Association and Mr. Elston Grubaugh, General Manager for the Wellton-Mohawk Irrigation and Drainage District. Hank and Elston provided valuable insight on the operational plans and potential impacts on their districts that have different priority levels for Colorado River water allocations.

The discussions in both the keynote and breakout sessions were very direct, candid, and forthright. Mr. Buschatzke and Mr. Hamby both provided very thorough and informative descriptions of how the negotiation teams are structured, their function, and how the negotiations have been proceeding.

In my opening presentation of the keynote program, I described my impressions from a remote position, not being directly involved in any manner in the negotiations, that two basic schools of thought seem to have developed and appear to be dominant in the current negotiation impasse. The first apparent school of thought in the development of the new guidelines is to follow the law, specifically the Law of the River. The other school of thought is to essentially tear up the existing set of agreements, burn it all down – so to speak, and start over completely. It seems that these two schools of thought are generally held by the lower and upper basins, respectively. Tom Buschatzke offered a third possibility that could develop as a hybrid plan between the two.

Hank Auza and Elston Grubaugh provided valuable perspectives as Colorado River water users working with varying levels of legal priority for water allocations. They and their colleagues working in the various irrigation districts of the lower Colorado River Valley have a lot at stake with these negotiations and the future health of the river. Their input was also very direct, complete, and forthright. Their experience and point of view brought a lot of valuable information to these discussions for the benefit of everyone present and participating.

Collectively, both the keynote and breakout sessions dealing with the future of the Colorado River were very well delivered by Tom Buschatzke, J.B. Hamby, Hank Auza, and Elston Grubaugh. Their hard work and commitment to the good stewardship of Colorado River water resources is clear and we are very fortunate to have them each committing their time and expertise to these issues.

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.

PBS News recently did a story on the importance of Yuma’s winter vegetable production and the pressures the Western US is facing due to water scarcity. The story features insights from local growers Matt McGuire, JV Smith Companies and Jon Dinsmore, Dinsmore Farms, as well as Arizona Department of Agriculture Director, Paul Brierley. The report is well done, covering the basics of Yuma agriculture and the water shortage issues the industry is facing. It’s a quality piece, worth a listen.

Check it out by clicking here or on the image below.

Fig. 1. PBS NewsHour: “Arizona Farmers Forced to Adapt as Main Water Source Dries Up” story. (Photo Credits: PBS News)

We are receiving some summer grass samples for identification. As you know the seedlings look very similar. 
PCAs have mentioned, and we can corroborate that some species respond differently to herbicides. As an example, we have seen that Sprangletop (Leptochloa filiformis) is not controlled with selective postemergent herbicides like Fusilade or Poast.  We have seen only good results with a high rate of clethodim (Select), and the generics off the same active ingredient. Sandbur is also tolerant to these herbicides.
These two weeds frequently come back from crowns surviving the winter which makes spring preemergence herbicides applied ineffective.
The following are common species of summer annual grass here:
 

echinochloa	water grass and barnyard grass
leptochloa	red sprangletop and mexican sprangletop
eriochloa	southwestern cupgrass and prairie cupgrass
cenchrus	field sandbur and red sandbur
setaria	green foxtail and yellow foxtail and
chloris	feather finger grass and truncate finger grass

 
 Check out the Summer Annual Grass ID publication which contains pictures and descriptive characteristics of each of these species.

Calvin’s lab conducted an experiment this fall to evaluate bioinsecticides that can help to control pale striped flea beetles inorganic crops. The experiment was conducted at the Yuma Agricultural Center experimental farm. Four insecticides and insecticide mixes, including Biolink (insect& bird repellent), Biolink + Pyganic, Pyganic, and M-Pede + Entrust, were evaluated along with a nontreated check. Insecticide treatments were applied using chemigation through sprinklers during the last 40 minutes of germination water. Each treatment was applied to a strip of 10 beds of cabbage, and each strip was divided into 4 subsections representing 4 replications. Precautions were taken to avoid cross-contamination across treatments. Because there was a stand issue, stand count data was not considered for evaluation. The treatments were compared using the percentage of damaged plant data. This data was collected by inspecting 20 plants per subsection. We also inspected each of these 20 plants and their immediate surroundings for the presence of flea beetle adults. While we observed a lot of flea beetle damage, we only saw one flea beetle throughout the experiment. The assessment was made on the 4thand the 7th day after application (DAA).

At 4 DAA, all insecticide-treated strips showed a comparable reduction in injured plants. However, only Biolink, Biolink +Pyganic, and M-Pede + Entrust exhibited a level of injured plants that was significantly lower than that of the non-treated control. At 7 DAA, only Biolink showed injured plant incidence that was significantly lower than that of the non-treated control. However, Biolink + Pyganic, and M-Pede + Entrust were comparable to the Biolink alone treatment (Figure 1). The data suggests that the evaluated bioinsecticides and bioinsecticide mixes can be used alternatively when targeting pale striped flea beetles in brassica seedlings. However, an additional application after 4 DAA would be necessary for better protection of the crop.

Figure 1a. Brassica plant with flea beetle feeding injury


Figure 1b. Adult pale striped flea beetle.


Figure 2. Means percentage of cabbage plants damaged by flea beetles. Bars
with the same capital letter or lowercase letter are not statistically different. IBR
= Biolink (insect & bird repellent).

In the February 5, 2025 issue of the Arizona Vegetable IPM Newsletter, the potential benefits of biostimulants in lettuce production were highlighted. These naturally derived substances like seaweed extracts, microbial inoculants, and humic acids are known to improve soil health, enhance crop growth rates, and boost both yield and yield quality in lettuce farming. However, a critical question arises: Is the biostimulant safe for my organic and/or conventional lettuce farming?

Safety is paramount, especially for leafy greens like lettuce that go directly from the field to the consumer’s plate or bowl. Consumers expect high-quality produce that is not only nutritious but also free from harmful residues. This concern drives the need for a careful evaluation of any new agricultural input.

Biostimulants could offer several potential promising benefits for lettuce production by enhancing various aspects of plant and soil health. They improve soil health by increasing microbial diversity and boosting organic matter content, which leads to better soil structure and improved water retention. Additionally, biostimulants promote enhanced crop growth by stimulating root development and nutrient uptake, resulting in more vigorous and resilient plants.

When considering biostimulants, growers should be mindful of both the source and composition of the products used. Biostimulants come in two main forms: microbial, which contain beneficial bacteria or fungi such as Bacillus spp. or mycorrhizae, and non-microbial, which are derived from organic sources like seaweed extracts, humic acids, or amino acids. Along with these benefits, it is crucial to manage potential contaminant risks. For instance, microbial biostimulants may carry pathogens that pose food safety risks, while certain formulations might contain trace levels of heavy metals or residues that exceed safe limits. To ensure the safety of lettuce, growers can adopt proper application methods and timing: applying biostimulants to the soil generally carries a lower risk, as soil microbes help break down contaminants, whereas foliar applications done too close to harvest could leave undesirable residues on edible leaves. By carefully selecting products and adhering to these guidelines, growers can harness the benefits of biostimulants while maintaining the safety and quality of their lettuce crops.

To further assess biostimulant safety, growers should check for certifications such as an OMRI listing or third-party organic approval and adhere to Good Agricultural Practices (GAPs) by applying biostimulants at safe intervals before harvest.

Take-Home Message: For optimal safety and effectiveness, consider applying biostimulants using subsurface drip irrigation instead of foliar spraying, and avoid applications close to harvest. When possible, opt for non-microbial formulations to further minimize any risks.

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.