Many of you are aware of, or are using the recent PrimusGFS v3.2 Module 9 - IPM Practices that have been adopted by many growers. They require PCAs to document their IPM practices when scouting fields and making IPM decisions. One of the main requirements for compliance of the plans is to have a though understanding and use of Action thresholds (AT) in making management decisions. To assist PCAs with this, I have developed an Extension publication that defines ATs and includes ATs for the major pests found in leafy vegetables and brassica crops. This publication can be found at this link: Action Thresholds for Desert Produce Crops.

In produce crops, insecticides play an essential role in preventing crop losses and satisfying market demands for cosmetically clean and insect free produce. However, insecticides should only be applied when necessary. When commonly used cultural, physical, and biological control practices fail to adequately protect the crop, an insecticide application is required. Application timing should be based on a locally developed Action Threshold. The AT is a decision-making tool that triggers a control action (i.e., insecticide application) when the insect density or damage on the crop approaches a level known to reduce yields or quality. Once the AT is reached or exceeded, an insecticide should be applied as soon as possible to prevent economic losses. In desert produce there are three types of ATs commonly used:

Prevention: This approach recommends a prophylactic application against a pest that is known to immediately infest or damage the crop upon seedling emergence during stand establishment. Experience has shown that preventative insecticide applications against these pests can quickly prevent unnecessary stand or yield losses. Preventative applications often reduce overall foliar insecticide use. An example would be the use of imidacloprid applied at planting for whiteflies or aphids.

Nominal Action Threshold: The most common thresholds for foliar insecticide use in leafy vegetables are based on expert opinion and the best available evidence on potential for economic harm. These ATs are based on quantitative insect density or damage levels, are developed by experienced Extension entomologists through field research and experience. The ATs in this document were developed and refined over the past 30 years from research conducted at the Yuma Agricultural Center. An example AT would be to treat for bagrada bug when >5% of plants have fresh feeding damage on cotyledons or leaves.

Zero-Threshold: When insect contamination at harvest is not tolerated by produce shippers or buyers, a prophylactic spray just prior to harvest can be applied to eliminate insect contaminates (trash bugs) from infesting the marketable portions of the crop.

Finally, a good scouting program is essential in Leafy Vegetable IPM. Scouting is all about making informed management decisions. Frequently sampling plants in the field allows PCAs to determine the level of insect infestation or plant damage occurring, and if the AT has been reached or exceeded. Sampling also allows PCAs to avoid unnecessary spraying.

For more information see: Action Thresholds for Desert Produce Crops.

Dr. J S. Famiglietti, is a Global Futures Professor and hydrologist with the School of Sustainability at Arizona State University (ASU) and he serves as the director for ASU’s Arizona Water Innovation Initiative. Famiglietti and his colleagues recently published an article in the Geophysical Research Letters journal (Abdelmohsen et al., 2025) with the American Geophysical Union (AGU) that describes the declining groundwater supplies in the lower Colorado River basin (LCRB). The methods for conducting this analysis are described in other publications (Rodell, Famiglietti et al., 2004; Rodell, Houser et al., 2004).

This research is valuable in providing important information regarding the current and future management of the Colorado River and LCRB groundwater supplies. In Arizona, 36% of the state’s water supply comes from the Colorado River and 41% from groundwater (Figure 1, ADWR, 2025). Agriculture uses 72% of the total Arizona water supply (Figure 2, ADWR, 2025).

As surface water supplies in the Colorado River have diminished over the past 25 years due to the ongoing drought in the southwest, conservation measures have resulted in reductions of allocations from the river. In response many areas, e.g. central Arizona, have turned to increasing groundwater withdrawals to supplement the difference.

In many discussions regarding the future management of Arizona water resources, groundwater sources are often considered for possible use and planning. In parts of the state with Active Management Areas (AMAs) there is a 100-year water supply requirement that must be proven before land can be developed (Figure 3; 1980 Groundwater Management Act (GWMA), Arizona Department of Water Resources (ADWR) 2017). Groundwater resources are often listed as future sources for development.

The Arizona GWMA has helped reduce groundwater depletion rates in some of the AMAs. But based on ADWR projections, some of the AMAs will not be able to meet the sustainability goals set in the GWMA to achieve safe yield by 2025 (ADWR, 2016, 2020). In addition, the Phoenix AMA is projected to encounter complete depletion by the end of the century based on groundwater simulations (ADWR, 2023).

It is important to note that only 18% of Arizona (by area) is subject to groundwater management, highlighting the urgent need for broader and more effective groundwater management across the entire LCRB.

Making assumptions on resources that might not exist is dangerous and reckless. In the process of trying to prove a 100-year water supply with a changing climate, the inclusion of groundwater resources are increasingly important. It is essential that we deal with facts and the truth and not hopeful thinking in planning for the future with issues like water resources.

This recent work by Abdelmohsen et al., (2025) is important in that it provides a good estimate of the groundwater supplies across the LCRB. Their results show very severely diminished levels of groundwater supplies in many parts of Arizona (Figure 4). Overall, this is good work with good methodology and conclusions.

However, in one aspect I believe their conclusions are flawed regarding their recommendations for agriculture to simply move away from water-intensive crops and flood irrigation and to utilize low-water use crops and irrigation systems such as drip irrigation to reduce overall water demand. That is a nice simple theory, and it is commonly advocated by scientists working in this arena and others that are probably well-intended but poorly informed of the facts (Richter et al., 2023 and Famiglietti, 2014).

Important conclusions from this study show that because of the increasing aridification along with increasing demand in this region, between 2015 to 2024 the level of groundwater storage across the LCRB decreased by a factor of 3. It is estimated that a total of 42.3 million acre-feet (MAF) of water has been lost in this period across the entire basin from all sources and that 27.8 MAF of this loss was from groundwater, which is estimated to be roughly equivalent to the full Lake Mead capacity.

Abdelmohsen et al., (2025) suggest that progress towards groundwater sustainability in the Colorado River basin could be achieved by reducing current annual extraction in balance current rates of depletion. This translates to a reduction in current annual groundwater depletion of 0.35 km3/year (0.28 MAF) in the upper basin and 1.5 km3/year (1.22 MAF) in the lower basin.

To put that in perspective, the total annual water consumption in Arizona is approximately 7.0 MAF (ADWR, 2025). The Drought Contingency Plan reduction for Tier 1 in Arizona is 512 thousand acre-feet (KAF) and Tier 2a is 592 KAF.

With a current population of 7.6M in Arizona and a projected population of 8.9 to 9.6M people by 2050, the pressures and competition for water among all sectors will be increasingly intense. In Maricopa County, the population is projected to reach between 6.0 and 7.0M by 2050.

Arizona agriculture will be continually forced to deal with the increasing urban population and the diminishing water supplies. The recent results coming from Abdelmohsen et al., (2025) provide a valuable assessment of groundwater supplies in the LCRB and Arizona and the importance of conservation measures.

This also reinforces the critical need for Arizona to develop functional groundwater legislation for areas beyond the established AMAs.

Figure 1. Sources of the Arizona water supply. Source: Arizona Department of Water
Resources (ADWR).


Figure 2. Arizona’s water use by sector. Source: Arizona Department of Water Resources
(ADWR).


Figure 3. One-hundred-year water supply requirements for Active Management Areas in
Arizona. Source: ADWR, 2025.


Figure 4. Categorization of groundwater basins based on water usage in the LCRB. (a) This
classification map utilizes data from the University of Arizona and the Arizona Department
of Water Resources (ADWR, 2016) to show the predominant source of water. Basins with
significant access to surface water are shown in blue; (b) TWS trends (mm/year) from
GRACE/FO for the groundwater basins in (a). The basins with the greatest loss rates are
shown by progressively darker red colors. Source: Abdelmohsen, et al. 2025.

References:

Abdelmohsen, K., Famiglietti, J. S.,Ao, Y.Z., Mohajer, B., & Chandanpurkar, H. A. 2025. Declining fresh water availability in the Colorado River basin threatens sustainability of its critical groundwater supplies. Geophysical Research Letters, 52,e2025GL115593. https://doi.org/10.1029/2025GL115593

Arizona Department of Water Resources (ADWR).2016. Arizona's strategic vision for water supply sustainability. Arizona Department of Water Resources (ADWR). Retrieved from https://new.azwater.gov/sites/default/files/ADWR_2016_Strategic_Vision.pdf

Arizona Department of Water Resources (ADWR). 2017. 1980 Groundwater Management Act. https://www.azwater.gov/news/articles/2017-01-23-3

Arizona Department of Water Resources (ADWR).2020 Arizona groundwater management report for active management areas 2020. Arizona Department of Water Resources (ADWR). Retrieved from https://new.azwater.gov

Arizona Department of Water Resources(ADWR). 2023. Groundwater sustainability simulations: 2023 Phoenix AMA groundwater outlook. Arizona Department of Water Resources (ADWR).

Arizona Department of Water Resources.2025. Arizona’s Water Supplies. https://www.arizonawaterfacts.com/water-your-facts

Famiglietti, J. S. 2014. The global groundwater crisis. Nature Climate Change, 4(11), 945–948. https://www.nature.com/articles/nclimate2425

Richter, B. D., Ao, Y., Lamsal, G., Wei, D., Amaya, M., Marston, L., & Davis, K. F. 2023. Alleviating water scarcity by optimizing crop mixes. Nature Water 2023, 1(12), 1035–1047. https://www.nature.com/articles/s44221-023-00155-9

Rodell, M., Famiglietti, J. S., Chen,J., Seneviratne, S. I., Viterbo, P., Holl, S., &Wilson, C. R. (2004a).Basin scale estimates of evapotranspiration using GRACE and other observations. Geophysical Research Letters, 31(20), L20504. https://doi.org/10.1029/2004GL020873

Rodell, M., Houser, P. R., Jambor, U., Gottschalck, J., Mitchell, K., Meng, C.‐J., et al. (2004b). The global land data assimilation system. Bulletin America Meteorology Social, 85(March),381–394. https://doi.org/10.1175/BAMS853381

 

It is with sadness and a sense of loss that we share the news that our friend and colleague, John Palumbo passed away last weekend. John and I have been office mates so to speak, only two doors apart, for the past 17 years. What I will miss most about John is his presence. Warren Buffet said that a key to becoming a better person was to surround yourself with people that are better than you. In other words, hangout with people who had traits and characteristics that you admire and want to emulate. John was one of those people. He made you want to be a better person. We will miss you, John. RIP.

My name is Mazin Saber, and I serve as an Associate in Extension specializing in Weed Management at the School of Plant Sciences, University of Arizona/Yuma County Cooperative Extension, based at the Yuma Agricultural Center. My work focuses on developing innovative site-specific weed management strategies tailored to specialty crop systems in desert agriculture, aiming to establish effective and sustainable weed control programs. I currently lead a new weed control research initiative at the Yuma Agricultural Center.

My academic background includes a Bachelor’s degree in Agricultural Mechanization and a Master’s degree in Agronomy from the University of Basrah, Iraq. I also hold an M.E., and Ph.D. in Agricultural and Biological Engineering from the University of Florida, where my doctoral research focused on designing automated mechanical intra-row weed control system for row crops.

Previously, my research has involved quantitative assessment of crop water-use and salt balance in the Lower Colorado River region. By utilizing advanced tools such as Eddy Covariance to measure evapotranspiration across 14 major crops over multiple seasons on commercial farming, I have contributed to improving water use efficiency and enhancing the sustainability and competitiveness of desert agriculture.

As I build my weed management program, I am conducting an assessment survey to identify the most pressing weed management challenges. Your feedback is crucial to ensure this program meets your needs. Please take a few minutes to complete the survey using the link below.

https://uarizona.co1.qualtrics.com/jfe/form/SV_4Od09r4hPLThLz8

I am available for any discussions about weed issues on your farm and I am happy to arrange field visits or ride-alongs to better understand your specific challenges. Please feel free to reach out to me directly.

Email Mazin

Diamondback moth (DBM) has become a major challenge for Arizona brassica growers, with increasing reports of insecticide resistance and difficult fall and spring seasons.

To address this challenge, University of Arizona Extension entomologists and the Arizona Department of Agriculture, led by Dr. Wilfrid Calvin, collaborated to create new, practical guidelines for managing DBM in both transplant production and field settings.

The document offers practical, Arizona-focused strategies that can help prevent DBM and improve control.

The document can be found here: Guidelines for Effective Management of Diamondback Moth in Brassica Crops

We are pleased to share our recently published Extension article that investigates the impact of biostimulant applications on iceberg lettuce production under organic and conventional systems using subsurface drip irrigation in Yuma, Arizona. This study, conducted during the 2024–2025 season on a one-acre research field, examined how traditional and sensor-based irrigation scheduling, combined with biostimulant, influence crop growth, development, and yield.

Our findings revealed that while biostimulant had a limited effect on plant height in organic lettuce and only modest improvements in conventional production, the integration of biostimulant use with sensor-based irrigation increased yields. In the organic system, this combined approach increased yields up to 16.7 tons per acre. Similarly, in the conventional system, it achieved yields as high as 27 tons per acre, comparable to other conventional treatments. To read the full article and learn more about the study and its practical implications, please visit: Evaluating Biostimulant Effects on Growth and Yield of Iceberg Lettuce.

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

 

Corn earworm: CEW moth counts remain at low levels in all areas, well below average for this time of year.

Beet armyworm: Trap increased areawide; above average compared to previous years.

Cabbage looper:  Cabbage looper counts decreased in all areas; below average for this time of season.

Diamondback moth: DBM moth counts decreased in most areas. About average for this time of the year.

Whitefly: Adult movement beginning at low levels, average for early spring.

Thrips: Thrips adult counts reached their peak for the season. Above average compared with previous years.

Aphids:  Aphid movement decreased in all areas; below average for late-March.

Leafminers: Adults remain low in most locations, below average for March.