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.At events and in the halls of the Yuma Agricultural Center, I’ve been hearing murmurings predicting a wet winter this year…
As the Yuma Sun reported last week, “The storms of Monday, Aug. 25 [2025], were the severest conditions of monsoon season so far this year in Yuma County, bringing record-rainfall, widespread power outages and--in the fields--disruptions in planting schedules.”
While the Climate Prediction Center of the National Weather Service maintains its prediction of below average rainfall this fall and winter as a whole, the NWS is saying this week will bring several chances of scattered storms.
These unusually wet conditions at germination can favor seedling disease development. Please be on the lookout for seedling disease in all crops as we begin the fall planting season. Most often the many fungal and oomycete pathogens that cause seedling disease strike before or soon after seedlings emerge, causing what we call damping-off. These common soilborne diseases can quickly kill germinating seeds and young plants and leave stands looking patchy or empty. Early symptoms include poor germination, water-soaked or severely discolored lesions near the soil line, and sudden seedling collapse followed by desiccation.
It is important to note that oomycete and fungal pathogens typically cannot be controlled by the same fungicidal mode of action. That is why an accurate diagnosis is critical before considering treatments with fungicides. If you suspect you have seedling diseases in your field, please submit samples to the Yuma Plant Health Clinic or schedule a field visit with me.
National Weather Service Climate Prediction Center: https://www.cpc.ncep.noaa.gov/
National Weather Service forecast: https://forecast.weather.govVegetable season is well underway and early planted vegetable crops are already about one month old. Many fields have or soon will need to be cultivated. As such, I thought it would be timely to “repost” this video on “new” technologies for cultivating weeds - 1) a camera-guided side-shift hitch and 2) finger weeders, an in-row weeding tool (Fig. 1). The video shows the device operating in seedling corn, but it will work similarly in other crops such as broccoli or cauliflower.
We have found the devices work well. Trials conducted in cotton over 3 years showed that use of camera-guidance improved weed control by more than 30% and finger weeders removed about 45% of the in-row weeds. Weed control using the two technologies together simultaneously was roughly 90% for broadleaf weeds and about 85% for all weed species including grasses.
If you are interested in trying these technologies, please contact me. We still have the equipment and I’d be happy to work with you.
Fig. 1. Technologies for precision cultivation and in-row weeding include a) a
camera-guided side-shift hitch attached to a cultivator and b) in-row weeding
tools (finger weeders).
Watch the Video Below
Question to IPM team:
I applied Raptor and Pursuit to an alfalfa field. Can you provide some information on the carryover and phytotoxicity to onions?
IPM Team: We haven’t done plant back evaluations with these products. The soil persistence that is mentioned in the AZ PCA study guide is 2-4 months for the Raptor and 3-12 months for Pursuit. The label specifies longer replanting intervals for various crops and suggests that “before planting any crop not listed elsewhere in Rotational Crop Restrictions, a successful field bioassay must be completed. The field bioassay consists of a test strip of the intended rotational crop planted across the previously treated field and grown to maturity”.
An interesting journal article “Injury to Vegetable Crops from Herbicides Applied in Previous Years”, mentions In 1995, residual imazethapyr delayed tomato maturity but did not reduce tomato yield. Other vegetable crops were not injured by herbicide residues. Then in 1997 “imazethapyr carryover injured cabbage, onion, and tomato plants and reduced tomato yield most injury occurred at 2X and 4X rates1.
The “Carrington Research Center in NDSU did an herbicide carryover study included here which presents the “response of onions to herbicides applied to soybean the previous year2” including Raptor and Pursuit. Also, in this study (table below) onion injury was significant in the 2X and 4X rates.
Another “Evaluation of Pre and Post Emergence Herbicides on Yield Contributing and Quality Characters in Onion” found that “Imazethapyr @ 100 g a.i / ha as post emergence application (20 DAT) coupled with preemergence herbicides produced the lower (yield) values than weedy check as Imazethapyr found to be toxic to the Onion3”.
The field study “Efficacy of imidazolinone herbicides applied to imidazolinone resistant maize and their carryover effect on rotational crops” showed sensitivity of rotational crops, from high to low, was the following: Beta vulgaris>Capsicum annum>Lycopersicum esculentum>Cucumis melo>Hordeum vulgare>Medicago sativa>Lolium multiflorum>Avena sativa>Pisum sativum>Allium cepa (onion)>Zea mays.
The label’s recommendation of doing a bioassay is very useful. Many factors can affect herbicide carryover and every case is different. Low soil moisture might not permit appropriate soil conditions for an efficient microbiological and chemical degradation of imidazolinone herbicides3. Other elements to consider are the soil texture, pH, soil temperature, microbial activity, photodegradation, previous crop, water applied after application of the herbicide, soil tillage intensity. The combinations of these elements could contribute to dissipation of these products. Also, having this information would help us determine the best IPM strategy.
References:
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 most over the last month, but increased activity in Wellton and Tacna in the past week; above average for this time of season.
Beet armyworm: Moth trap counts increased in most areas, above average for this time of the year.
Cabbage looper: Moths remain in all traps in the past 2 weeks, and average for this time of the season.
Diamondback moth: Adults decreased to all locations but still remain active in Wellton and the N. Yuma Valley. Overall, below average for January.
Whitefly: Adult movement remains low in all areas, consistent with previous years.
Thrips: Thrips adults movement decreased in past 2 weeks, overall activity below average for January.
Aphids: Winged aphids are still actively moving, but lower in most areas. About average for January.
Leafminers: Adult activity down in most locations, below average for this time of season.
