Regenerative agriculture (RA) crop production systems have recently been popularized in many agricultural communities. Claims are often made that RA systems are better than conventional agriculture (CA) crop production systems, which are commonly considered to be input intensive.

The definition of an RA system is highly dependent on the practitioner, and many definitions can be found. In general, RA is a principles-based approach that aims to restore and enhance soil health, biodiversity, and ecosystem services through practices such as reduced tillage, cover cropping, diverse rotations (including fallow or resting periods), crop residue retention. In some cases, it includes agroforestry and/or the integration of livestock.

Proponents of RA argue that it can increase soil organic carbon (SOC), which is a proxy measurement related to stable soil organic matter (SOM). They also contend that RA practices improve soil water-holding capacity and soil systems resilience (which is an extremely broad category).

Regenerative agriculture systems have the basic objective of increasing on-farm biodiversity and delivering long-term improvement in productivity and soil health as compared to conventional crop production systems.

Recent reviews of the literature have addressed the overall trends in field research associated with RA systems in comparison to CA crop production systems. Some studies have demonstrated some positive effects of RA systems on soil condition and soil health.

Research reviews clearly illustrate that the context of the studies is very important in interpretation and there is clear evidence of major gaps in describing and quantifying effects from RA systems (Montgomery and Biklé, 2021 and Khangura, et al., 2023).

BLUF (Bottom Line Up Front) Statement:
Regenerative systems promote crop and soil management practices that have been recognized and utilized for many years, hundreds of years in fact. Current research comparing RA and CA systems are highly variable. All asserted benefits of RA systems are highly dependent on climate conditions and the CA systems used for comparison.

Overall, RA practices generally contribute positively to soil health. However, there is no definitive evidence of RA systems being superior to CA crop production systems.

Pros – Objectives of RA systems:

• Soil carbon and structure. A meta-analysis of temperate systems found that reduced tillage and inclusion of grass-based rotation and resting/fallow periods could increased SOC relative to CA. Studies in cooler and humid climates show that RA practices can build SOC stocks over several decades (Jordan, et al., 2022). This does not transfer to other agroecosystems in drier and warmer environments.
• Soil health and resilience. Practices that increase incorporation into soil crop residues (organic material), crops with different types of root systems, and crop rotations that include legume crops can improve soil aggregate stability, infiltration, internal soil drainage, and retention has been found in some studies and reviews (Khangura, et al., 2023).
• Biodiversity and ecosystem services. Diversified crop rotations, the use of cover crops, and crop–livestock integration can increase soil biodiversity. It is also contended that crop pollination and pest-regulation (insects, weeds, and diseases) can be improved with RA systems versus CA. However, these effects are commonly poorly quantified in most studies (Sher, et al., 2024). Thus, some of these benefits are quite speculative.
• Co-benefits and livelihoods. There are some publications that conclude that RA systems can be more profitable or financially resilient for farmers. But from these studies it is only possible for RA superiority to CA systems when there are price premiums, reduced input costs, or ecosystem payment schemes that are available. Highly variable yields, the need for policy support and payment mechanisms are commonly needed to make RA systems viable at scale (Reuters, 2024).

Cons / limitations compared to conventional cropping systems:

• Yield uncertainty and trade-offs. In most studies, RA practices do not consistently or significantly change crop yields relative to CA systems, particularly in short-term studies, anything less than a decade. Overall, review of the literature shows no consistent or general “win-win” RA situation that will reliably increase yields while increasing SOC. Yield responses are highly variable by crop, region, and the time elapsed since RA systems were adopted. In many cases, the transition years into RA systems cause yield reductions. The site-specific constraints can be quite variable it is difficult to identify consistent positive trends in RA system benefits over CA systems (Jordan, et al., 2022).
• Greenhouse gas and livestock trade-offs. RA systems that integrate livestock or increasing manure inputs can boost SOC and encourage soil biodiversity. These

types of RA systems have been shown to raise methane and nitrous oxide emissions. As a result, any net climate benefits are dependent on whole-system greenhouse-gas accounting, which is often not done or effectively included in most RA studies (Sher, et al., 2024).

• Evidence gaps and heterogeneity. Most of the cases found in the current literature on RA systems evaluation address single practices such as no-till versus conventional tillage, the use of cover crops, and animal manure application regimes. There is a substantial absence of long-term, fully integrated RA/CA systems comparisons. Accordingly, the results found in the current literature are highly variable and context dependent (soil type, climate, access to RA-friendly market benefits, etc.). As a result, generalization is extremely limited in comparing RA and CA systems (Jordan, et al., 2022).
• Adoption barriers. Moving to RA systems often requires new knowledge, increased and different levels of labor reallocation, equipment changes, and often many upfront investments to access unique markets and secure technical support. Incentive structures (i.e., subsidies) are commonly needed to make RA system transitions from CA systems and without that, adoption can be slow and highly variable (Reuters, 2024).

Regenerative systems promote crop and soil management practices that have been recognized and utilized for many years, hundreds of years in fact. Current research comparing RA and CA systems are highly variable. All asserted benefits of RA systems are highly dependent on climate conditions and the CA systems used for comparison.

There is a definite need for long-term, system-level experiments. The appropriate measurement and quantification of RA and CA system management comparisons and soil health parameters are essential priorities to help resolve the many remaining uncertainties associated with RA systems (Jordan, et al., 2022).

Overall, RA practices can potentially improve soil health. However, there is no definitive evidence of RA systems being superior to CA crop production systems.

References:
Jordon, M. W., K. J. Willis, P. C. Bürkner, N. R. Haddaway, P. Smith, & G. Petrokofsky. 2022. Temperate regenerative agriculture practices increase soil carbon but not crop yield — a meta-analysis. Environmental Research Letters 17(9):093001. doi:10.1088/1748-9326/ac8609.  

Khangura, R., D. Ferris, C. Wagg, & J. Bowyer. 2023. Regenerative agriculture—A literature review on the practices and mechanisms used to improve soil health. Sustainability 15(3):2338. doi:10.3390/su15032338.  

Montgomery, D. R., & A. Biklé. 2021. Soil health and nutrient density: Beyond organic vs. conventional farming. Frontiers in Sustainable Food Systems 5:699147. doi:10.3389/fsufs.2021.699147.  

Sher, A., H. Li, A. Ullah, Y. Hamid, B. Nasir, & J. Zhang. 2024. Importance of regenerative agriculture: Climate, soil health, biodiversity and its socioecological impact. Discover Sustainability 5:462. doi:10.1007/s43621-024-00662-z.  

Reuters. 2024. Rewarding farmers for regenerative agriculture is 'critical for decarbonising the food sector'. Reuters, June 10, 2024. (news article).  

Guardian (news). 2024. Cows help farms capture more carbon in soil, study shows. The Guardian, Sept. 28, 2024. (news article).  

Click here and hit ‘download’ for a PDF version of this article. 

First, I want to thank everyone who participated in last week's Vegetable Pest Losses Survey.  

This year's survey included the return of the lettuce disease losses section. While several diseases were present and managed last season, downy mildew accounted for the majority of disease management costs by a wide margin. This really underscores the impact that last spring's unusually rainy weather had on disease development across the Yuma lettuce production region.

No one can predict exactly what this upcoming spring will bring, but there has been discussion about the possibility of a strong El Niño leading to an extended monsoon season. If that proves true, the conditions would once again support spring downy mildew development. The pathogen only needs about 3 to 4 hours of continuous leaf wetness to infect lettuce, so periods of overnight moisture, prolonged morning dew, or frequent rainfall when inoculum (spores) are present increase disease risk.

With that in mind, this seems like a good opportunity to review what is known about downy mildew and discuss strategies for its management.

Resistance in lettuce to Bremia lactucae, the causal oomycete pathogen behind downy mildew, is inherited in a gene-for-gene fashion, meaning one major gene product in the plant host interacts with one major gene product in the pathogen. When resistance is present, this leads to an incompatible interaction between plant and pathogen and results in complete immunity to infection. Resistance genes in these types of interactions most often encode a protein molecule that acts like a burglar alarm. These molecular sensors in the host bind to proteins secreted specifically by the pathogen, and when that happens a storm of defense responses is activated in the plant that excludes further infection. This is not the only mode of genetic resistance found in plants, but it is often the most drastic and effective against obligate parasites like downy mildew.

But this simple gene-for-gene interaction often puts incredible selection pressure on the pathogen populations to change such that they can get around the resistance. By losing the molecule that the plant detects in order to initiate a defense response, the pathogen becomes unrecognizable to the resistance genes a plant variety may have. Just like spraying the same mode of action over and over again leads to a pest population developing resistance to a pesticide, the same selection applies to genetic resistance. The longer a resistance gene is deployed in a region, the more likely the pathogen population is to change in response until that resistance gene is no longer effective at managing the disease.

One of the biggest challenges with lettuce downy mildew is that B. lactucae is constantly changing over time. It exists as many different races, where each race has a different reaction to the resistance genes bred into lettuce varieties. You can think of these races as different versions of the same pathogen. A lettuce variety that resists one race may still be susceptible to another.

These races are identified by testing them against a panel of lettuce varieties with known resistance genes. In the western United States, races are named by the International Bremia Evaluation Board-U.S. (IBEB-US) and are given names with a number followed by the country’s abbreviation, such as 8US, 9US, or 10US. The populations found in the western U.S. are different from those found in Europe, so each region uses its own independent naming system.

The downy mildew population has changed considerably over time. Earlier races (1US through 4US) are now rarely found in commercial lettuce production. During the 2000s and 2010s, races 5US through 8US became the most common. Race 9US was recognized after being detected repeatedly between 2015 and 2017, and the newest officially recognized race, 10US, was designated in 2025. Below is a pie chart showing the relative frequency of the races identified from 114 Yuma County downy mildew samples between 2023-2024:

Figure 1: Pathotyping results of 114 lettuce samples from Yuma County collected between 2023 and 2024. Data source: https://bremia.ucdavis.edu/bremia_database_main.php

 

The results show that much of the downy mildew population found in Yuma County is made up of novel strains of Bremia lactucae that have not yet been officially classified as a race. An official race is only recognized after it has been shown to be stable and widespread over multiple locations and growing seasons. These newer strains may disappear over time, or they may eventually become established and earn an official race designation. In the meantime, this means growers and lettuce breeders in Yuma County are often dealing with strains that can dodge the resistance in some lettuce varieties before those strains are common enough to be officially recognized. It also highlights why relying on resistance alone is not enough to manage the disease.

 

Table 1: Pathotyping and fungicide sensitivity results of samples from Yuma County collected in 2025.

This trend appears to be continuing. All of the downy mildew samples sent for race testing last season were identified as novel strains rather than known, officially designated races.

It's impossible to predict exactly how these new strains will respond to the resistance genes found in today's commercial lettuce varieties. However, because they have not been previously characterized, they are more likely to overcome existing genetic resistance than the races we already know about.

New strains develop naturally over time. They can arise when different strains exchange genetics (i.e. intermate) or through random mutations. When growers plant varieties with similar resistance packages over large areas, the pathogen population is placed under strong selection pressure. Any strain that happens to acquire the ability to infect those resistant varieties gains a major advantage and gets to reproduce without competition where other strains cannot. Over just a few disease cycles, those successful strains can become much more common in the population until they are the predominant strain overall.

An important point to remember is that the resistance bred into commercial lettuce varieties is not wearing out or becoming weaker over time. The genetics in the lettuce remain just as effective as when the variety was released. What changes is the pathogen. As the downy mildew population evolves new strains emerge that can bypass resistance genes that previously worked very well.

That means that varieties carrying resistance to races 5US through 10US are still doing exactly what they were designed to do. They continue to suppress those known races and help prevent them from becoming widespread in commercial fields. So, if you experience significant downy mildew in a field planted with a variety that has a strong resistance package, the culprit is most likely one of these newer, uncharacterized strains rather than a failure of the variety itself.

Unfortunately, Bremia lactucae can evolve much faster than scientists can identify new races and breeders can develop and release resistant varieties. That's why no resistance package should be viewed as a stand-alone solution.

This is also why extension, researchers, and the seed and crop protection industries place so much emphasis on the integrated pest management (IPM) concept. Genetic resistance is an essential tool, but it works best and remains the most sustainable when combined with other management practices. For novel strains that can slip past host resistance, timely fungicide applications and other disease management strategies become especially important for maintaining control.

Below are the results from last season's downy mildew fungicide efficacy trial, where we compared 12 fungicide programs under Yuma growing conditions.

 

Figure 2: Mean disease severity by treatment. Disease severity was determined by rating 10 plants within each of the five replicate plots per treatment using the following rating system: 0 = no downy mildew present; 1 = downy mildew present on bottom leaves of plant; 2 = downy mildew present on bottom leaves and lower wrapper leaves; 3 = downy mildew present on bottom leaves and all wrapper leaves; 4 = downy mildew present on bottom leaves, wrapper leaves, and cap leaf; 5 = downy mildew present on entire plant. Disease severity is displayed as the mean of five replicates across all three lettuce varieties and bars show a 95% confidence interval around the mean calculated from individual treatment data. Compact letter display (CLD) above boxes show significantly different treatments (Kruskal-Wallis ANOVA and Dunn’s test). Boxes sharing the same letter(s) are not significantly different from one another. Fb = “followed by” in the rotation. Not all products are registered yet for use in lettuce. The inclusion of specific fungicide products or formulations in these trials does not constitute an endorsement or recommendation over other labeled products.

 

The most effective way to manage lettuce downy mildew is to use an integrated approach. Plant varieties with a strong resistance package against races 5US through 10US, and pair that resistance with timely, full-label-rate fungicide applications when environmental conditions favor disease. This combination provides the broadest and most reliable protection against both known races and the novel strains that continue to emerge in Yuma County.

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

Interested in the latest developments in automated weeding machines and ag tech? There are a couple of opportunities at the upcoming 2025Southwest Ag Summit to stay up to date. One is the “Ag Tech: Innovations in Weed Control and Vegetable Crop Production Technologies” breakout session where university experts and cutting-edge innovators will provide updates on the latest advances in AI high precision smart spot sprayers and soil steaming for pest control (agenda below). The session will be held Thursday, February 20^th from 1:30-3:30 pm at Arizona Western College (AWC) in Yuma, AZ.

The other is the Southwest Ag Summit Field Demo on Wednesday, February19^th, where several of these technologies and other state-of-the-art automated weeders will be demonstrated operating in the field. The Field Demos will also be held at AWC. Breakfast will be served at 7:00 am and demonstrations begin at 8:00 am.

For more information about the Southwest Ag Summit, visit https://yumafreshveg.com/southwest-ag-summit/.

1. Precision Robotic Weeding and Thinning Trial
We are approaching the final steps of our ongoing robotic weeding and thinning trial for head lettuce. As the crop approaches maturity, we will soon conduct a comprehensive comparison of lettuce marketable yield between robotic-treated and handweeded/thinned plots.

These results will provide evidence-based insights into the efficacy and viability of robotic technologies in specialty crop production. Our preliminary observations suggest promising results, and we anticipate that detailed findings will be valuable for adoption decisions across the region.

Southwest Ag Summit Presentation
Join us at the Southwest Ag Summit on February 19th for a detailed presentation of our results. This session will provide the complete analysis to support grower decision making.

Funding Acknowledgment: This research was made possible through support from the Arizona Iceberg Lettuce Research Council (AILRC).

2. Precision Chemigation Trial
In parallel with robotic thinning and weeding research, we are advancing precision chemigation through the utilization of a custom injection assembly designed to accurately deliver chemicals like herbicides and pesticides into sprinkler irrigation systems for research purposes.

The chemigation assembly enables consistent, controlled injections at different rates, allowing for optimized chemical efficacy.

The chemigation trial will evaluate the efficacy of Kerb and Prefar herbicides applied at different rates through the chemigation system for head lettuce. This research will provide weed control efficacy optimized for chemigation delivery methods. We will present details on the chemigation system and herbicide efficacy during the IPM Session at the Southwest Ag Summit.

Funding Acknowledgment: This project was funded in part by the USDA National Institute of Food and Agriculture through the Western Integrated Pest Management Center.

Both projects represent important steps forward in the adoption of precision agriculture technologies for sustainable crop production. Results from both trials will be presented at the Southwest Ag Summit on February 19th.

For questions or to schedule a farm visit to view either trial, please contact Mazin Saber at mazinsaber@arizona.edu or cellphone# (352)870-8994. Stay tuned for the results! 

Bagrada bug (Bagrada hilaris) is an invasive stink bug recently established in the desert Southwest of the U.S. It has become a major economic pest of many cruciferous vegetable crops cultivated in fall and winter in the agricultural valleys of Arizona and southern California. Crop injury caused by Bagrada bug feeding has resulted in major economic losses. Depending on the crop species, Bagrada bugs may cause yield losses of 15-35%. Effective options for controlling Bagrada bug infestations in organic crops are limited, creating a significant challenge for organic growers. The objective of this study was to evaluate selective organic-approved insecticides to identify new tools that organic vegetable producers in the desert can use to manage Bagrada bugs effectively.

This fall growing season, we conducted a field trial to evaluate several organic-approved insecticides against the Bagrada bug in broccoli. The results of our trial show that M-Pede and a tank mix of M-Pede and Entrust can provide approximately a 60% reduction in Bagrada bugs relative to the untreated check. Captiva Prime and Neemix also resulted in a nearly 50% reduction in Bagrada bug numbers. Aza-Direct, Entrust alone, and Botanigard each resulted in about a 30% reduction in Bagrada bugs relative to the untreated check (Fig. 1). Our observations indicate that the insecticides evaluated are unlikely to provide quick knockdown. Tank mix of M-Pede and Entrust, Neemix, and Captiva Prime resulted in 39, 35, and 34% reduction in damage caused by Bagrada bug feeding. Entrust alone and M-Pede resulted in Bagrada bug feeding damage reductions approaching 25% (Fig. 2). Previous research trials conducted in Yuma also show that mixture of Entrust and M-Pede, Entrust alone, Aza-Direct, and Pyganic can fairly suppress the pest (Palumbo 2022).

Figure 1. Number of Bagrada bugs per 10 broccoli plants as affected by biological
insecticide applications, Fall 2025. All insecticide treatments included Nu-Film
P at 1 pt./ac.




Figure 2. Percentage of broccoli plants with damage caused by Bagrada bug
feeding, Fall 2025. All insecticide treatments included Nu-Film P at 1 pt./ac.

Additional Reading Material:
Palumbo, J.C. 2024. Bagrada Bug Management Tips - 2024. Veg IPM Newsletter, Vol. 15, No. 18 University of Arizona, Department of Entomology. http://hdl.handle.net/10150/676902

Keith, M., & Calvin, W. 2025. The Evolution of Bagrada Bug Management in Desert Cole Crops: The Legacy of John C. Palumbo (2010–2025). Veg IPM Newsletter, Vol. 16, No. 21. University of Arizona, Department of Entomology. http://hdl.handle.net/10150/678668

In a previous IPM Veggie Newsletter post, the figure labeling was published incorrectly. We apologize for the technical issues and are reposting the corrected reference and a brief recap focused only on the monthly average maximum air temperature (Tmax). Using the AZMET Yuma Valley station record (1987–2025), the figure for monthly average Tmax shows a gradual warming signal through time, with substantial year-to-year variability. The fitted linear trend indicates:

• Tmax slope: 0.036°F per year (≈ 0.36°F per decade)

Why it matters: From an agronomic and IPM perspective, a warmer Tmax baseline can contribute to faster degree-day accumulation, earlier crop development, and shifted timing of field operations and pest phenology. Even with large variability, the long-term direction supports continued use of temperature-based planning (degree-day tracking) to align scouting and management actions with development rates.

Figure 1. Distribution and long-term trend in monthly average maximum air
temperature (Tmax) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–
2025.

Tomorrow at the Southwest Ag Summit: Organic Practices (9:30–11:30 AM)

Tomorrow (Thursday, February 19, 2026) at the Southwest Ag Summit 2026 in Yuma, don’t miss the Organic Crop Production Methods seminar block (AS 113), running 9:30–11:30 AM. If you’re looking for practical, field-ready ideas to improve yield, strengthen soil health, and increase water-use efficiency in desert vegetable systems, this is one of the most relevant sessions on the program.

This fast-moving series brings together applied research and industry experience around what matters most in organic and transitional production under arid-region constraints: high pH/calcareous soils, salinity risk, intense evaporative demand, and tight irrigation windows. Presentations will emphasize organic fertility strategy and soil health–centered management, highlighting approaches that can translate into measurable gains in crop performance through improved nutrient availability, better infiltration and moisture retention, and management pathways that support root vigor and stress resilience.

Thursday presentations (9:30–11:30 AM)

• Organic Fertility Programs for the Sonoran Desert Region — Dr. Ramy Colfer (True Organic Products)
• Organic Fertility Management in Arid Soils — Patrick Roy (Wilbur-Ellis)
• Real-World Results from Liquid Natural Clay (LNC) — Dr. Shaddy Alshraah (Desert Control)
• Stronger Crops with Stronger Soils — Dave Booher (MyLand)
• Sudangrass Cover Crops in Organic Vegetable Systems of Imperial Valley — Dr. Aliasghar Montazar (UCCE)
• Cover Cropping Strategies for Vegetable Crop Production Rotations — Dr. Oli Bachie (UCCE)
• Impacts of Supporting Transitional Organic Producers — Dr. Sara Aly El Sayed (ASU)
• Sustainable Agriculture with Organic Production Practices — Dr. Ali Mohammed (University of Arizona) — Moderator

Program details: https://yumafreshveg.com/southwest-ag-summit/#FEB19

VegIPM Update Vol. 17, Num. 15

July 22, 2026

Results of trap catches below!!

 

Whitefly: Adult activity remains steady across locations; above average for this time of the year, especially high numbers seen in North Gila Valley. Historically, whitefly numbers peak in July.

Thrips: Adult thrips activity remained low over the last two weeks. About average for this time of the year. Historically, thrips numbers remain low until Sept-Oct.  

Diamondback Moth: No diamondback moths have been collected in the traps since May 19th.  Based on the past six years summer collection data, no DBM is collected in the traps in the summer months (Jun-Aug) until September.