In the past several years public interest in RA has increased along with other similar designations such as sustainable agriculture, organic agriculture, etc. (Figure 1). These and similar interests tend to go in cycles, and these systems are commonly treated as new, novel, and revolutionary. There is a consistent theme and set of practices among each of these systems and they are not all new. I describe them briefly in the following sections.
Regenerative agriculture (RA) is a systems approach to crop production that emphasizes rebuilding soil health, enhancing biodiversity, and increasing the resilience of farming systems by supporting natural ecological processes. Many RA practices are grounded in old agronomic principles that predate modern conventional/chemical agriculture (CA) and remain relevant in contemporary agroecosystems (Giller, et al., 2021).
Figure 1. The frequency of key terms in books (3-year rolling averages). Source:
Google NGram Viewer, Corpus ‘English 2019’ which includes books
predominantly in the English language published in any country (Giller et al.,
2021).
Crop rotations and diversification
Crop rotation has long been recognized as a beneficial agronomic practice, and it is central to RA systems. Rotations disrupt pest and pathogen life cycles, improve nutrient cycling, and stabilize crop yields. The inclusion of legumes contributes to biologically fixed nitrogen and diverse root systems, which can reduce fertilizer requirements and benefit subsequent crops (Solberg, 1958; Troeh, et al., 1999; Tilman et al., 2002).
Organic residues and manures returned to soil
The incorporation of crop residues, green manures, compost, and animal manures replenishes soil organic matter (SOM) and soil organic carbon (SOC). As they decompose, they provide slow-release nutrients, and support soil biota. Returning organic materials enhances microbial activity, improves soil structure, and benefits soil waterholding capacity. Farmers have been utilizing these practices to sustain soil productivity for centuries (Lal, 2004).
Minimal or reduced tillage
Reduced tillage and no-till practices protect soil structure, reduce erosion, and support soil biological communities. Limiting physical disturbance promotes soil aggregation, porosity, and water infiltration, contributing to improved soil stability. Reduced tillage has long been a component of soil conservation and soil-building strategies for many years, particularly in the past 90 years since the Dust Bowl (Solberg, 1958; Troeh, et al., 1999).
Cover crops
Cover crops planted between cash crops protect soil from erosion, scavenge nutrients, add biomass, and can suppress weeds. Living roots and added organic inputs stimulate microbial activity and promote a more diverse soil microbiome. In irrigated crop production systems this practice is more challenging and expensive due to the extra water demand and special practices for a crop with no cash value. Thus, it is impractical in most cases.
Mulching and residue management
Surface residues and organic mulches help conserve soil moisture, moderate soil temperatures, and in some cases reduce weed pressure. Mulching creates a favorable microclimate for beneficial soil organisms and contributes to soil protection (Solberg, 1958; Troeh, et al., 1999). This is also a centuries-old practice (Lal, 2004) but difficult to implement in many irrigated crop systems.
Agroforestry, hedgerows, and diversified landscapes
Some regenerative systems integrate trees, shrubs, or hedgerows with crops and livestock to enhance biodiversity and nutrient cycling and potentially diversify farm income. However, these practices are not feasible in all agricultural production systems, including irrigated crop production systems in the desert Southwest (Solberg, 1958). They have been found to be more feasible in tropical and subtropical regions.
Integrated pest management (IPM) and soil biology
Regenerative agriculture emphasizes the use of natural enemies, habitat for beneficial organisms, and reduced reliance on synthetic inputs. Most of these principles align with established IPM practices that have been successfully used for decades, including in Arizona crop production systems (Stern et al., 1959; Naranjo and Ellsworth, 2009).
Nutrient cycling and long-term soil organic matter (SOM)
Building or maintaining SOM is a primary objective of RA systems. Stable SOM improves soil structure, aeration, infiltration, and water-holding capacity. Maintaining SOM has long been recognized as a critical goal in CA systems as well (Tilman et al., 2002; Lal, 2004).
Agroecosystem management
Effective management is essential to the success of any crop production system and this is true in both RA and CA systems. Successful implementation requires integrating cropping system (agroecosystem) knowledge with careful planning, monitoring of soilplant relationships, and nutrient management to maintain yield stability and long-term sustainability. Efforts to do this practically and effectively are central to the management of crop production systems in the desert Southwest. We have realized good progress over many decades, yet it is always good to review and consider where we can continue to improve.
References
Giller, R.E., H. Renske, J.A. Andersson, and J. Sumberg. 2021. Regenerative agriculture: an agronomic perspective. Outlook on Agriculture, Vol. 50(1) 13–25.
Lal, R. 2004. Soil carbon sequestration to mitigate climate change. Science. 304: 1623-1627.
Naranjo, S.E. and P.C. Ellsworth. 2009. Fifty years of the integrated control concept: moving the model and implementation forward in Arizona. Pest Manag Sci 2009; 65: 1267–1286
Solberg, E.D. 1958. Planning for stability in a great area. In: Yearbook of Agriculture, 1958. p 532-536. United States Department of Agriculture, Washington, D.C.
Stern, V.M., R.F. Smith, R. van den Bosch, and K.S. Hagen. 1959. The integrated control concept. Hilgardia 29:81-101.
Tilman, D.; Cassman, K.G.; Matson, P.A.; Naylor, R.; Polasky, S. 2002. Agricultural sustainability and intensive production practices. Nature. 418: 671-677.
Troeh, F.R., J.A. Hobbs, and R.L. Donohue. 1999. Soil and Water Conservation: Productivity and Environmental Protection. Prentice Hall.
Among the diseases affecting global date palm production, trunk rot caused by Thielaviopsis spp. stands out as one of the most destructive and cryptic. That it because this broadhost necrotrophic fungus wreaks havoc on the tissues of palms but often shows no foliar symptoms until the tree is ready to collapse and is firmly beyond saving. Thriving in both arid and semi-arid production systems, Thielaviopsis trunk rot (TTR), also known as black scorch when it attacks foliage and flowers, can be problematic in the date palm production regions of the southwest and of landscape palms across the broader United States.
TTR, also called Medjnoon or Fool’s disease, is primarily caused by two related species of fungi from the genus Thielaviopsis. These fungal pathogens can affect a wide range of palm species, including true date palms (Phoenix dactylifera), Canary Island date palms, and other ornamental palms commonly used in urban landscaping. The disease can affect all palm tissues, and the tissue affected is determined by where the spores opportunistically meet an open wound of the host and begin their infection.
Once inside the palm, the fungus secretes an impressively diverse array of plant cell degrading enzymes before parasitizing and eating the tissue it kills. In trunk infections, TTR often leaves behind nothing but the tough, lignified, fibrous vascular bundles (see Figure 1), severely compromising the structural integrity of the palm and causing it to become crooked, collapsed, or to break off entirely often with little warning. Consequently, this can be extremely hazardous to any objects, equipment, or persons unlucky enough to be below the tree at the moment of collapse.
Figure 1: The trunk of a collapsed date palm. Only the thin, flexible fibrous bundles
remain, while other stabilizing trunk tissue has degraded to the point of snapping under
the weight of its own canopy.
In Arizona, there are no pesticides registered for use in edible-date palm production that show curative action once an infection is established. That makes preventative measures the primary choice when managing this disease. Because wounds are necessary for trunk infections, take note of potential sources of injury and where they arise. Trunk cracking due to excess water uptake, insect feeding damage, bird pecking, debris from windstorms, and mechanical damage from human activity are a few of the many sources of injuries associated with Thielaviopsis infection. Injury should be minimized, especially when other stressors are present with the host. Intentional wounds can be treated with copper solutions to deter the successful germination of the pathogens spores, but ensure the copper is present before the spores arrive and for the duration that the wound is fresh and not yet corked over.
Spores of these fungi survive both as resting structures in the soil and on dead palm debris. Spores can be moved from infected trees or residues to healthy trees by wind and rain splashing as well as pests moving from tree to tree. Infected trees should be removed as soon as possible after infection is confirmed, and infected remains should not be composted or recycled as mulches. Spores can also be moved mechanically on contaminated implements shared between trees. This makes the disinfection of tools and spikes vitally important to minimizing spread from infected trees to healthy trees.
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 20th 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, February19th, 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/.
The 2026 Yuma Southwest Ag Summit is just around the corner, and we’re excited to invite you to join us for a special session dedicated to cutting-edge weed management innovations and technology.
Field Demo: Wednesday, February 18
See the latest in precision weed control in action during our field demonstration day at the Arizona Western College, 2020 S Avenue 8E, Yuma, AZ 85365.
You will have the opportunity to watch intelligent robotic and mechanical weeding machines operate in real-world field conditions. This interactive demo is a great way to evaluate technology performance and talk directly with manufacturers and researchers about next-generation tools for vegetable production.
Session: Innovations in Weed Control and Vegetable Crop Production
Thursday, February 19 | 1:30–3:30 PM | Arizona Western College, Room AS 113 (2 AZ/CA and 2 CCA CEUs Approved)
Join us for a fast-paced lineup of talks highlighting the latest research and technologies shaping modern weed control systems:
Moderator: Dr. Mazin Saber, University of Arizona, Yuma County Cooperative Extension.
This session will offer practical insights, real data from field trials, and forward-looking discussions about robotic solutions for weed control. Whether you’re evaluating new equipment investments or looking for updates on research progress, this is a session you won’t want to miss.
We look forward to seeing you at the Southwest Ag Summit to explore how innovation continues to reshape weed management in desert vegetable systems.
The link below will take you to the complete agenda for the event.
https://acrobat.adobe.com/id/urn:aaid:sc:US:8e8d2658-6f01-41f0-9423-5f216ca6a64d
Diamondback moth (DBM), Plutella xylostella, is one of the most important insect pests of Brassica crops, including cabbage, broccoli, cauliflower, and some leafy greens. Heavy infestations can cause significant feeding damage, reduce crop quality, and increase production costs. Because DBM has a long history of developing resistance to insecticides, regular monitoring of insecticide susceptibility is essential to ensure effective management in the field. In the western United States, resistance to several key insecticide classes has been documented in field populations. For example, populations in California have shown high levels of resistance to several insecticide classes, including diamides, spinosyns, avermectins, pyrethroids, and Bacillus thuringiensis (Bt) products. More recently, outbreaks in Arizona have been associated with confirmed resistance to diamide insecticides and reports of reduced field efficacy. This highlights the importance of regular insecticide susceptibility monitoring and the implementation of resistance management strategies to maintain effective control of the pest. While field resistance and reduced efficacy reflect outcomes under production conditions, laboratory susceptibility monitoring provides a standardized approach to detect shifts in population response before or alongside observable field control issues.
To evaluate current insecticide susceptibility levels in DBM populations across Arizona's major Brassica-growing regions and some California populations, DBM larvae were collected from multiple locations in Arizona and California. DBM populations were reared in the laboratory and their progenies were tested under controlled laboratory conditions. Only one Arizona population was included in this initial assessment. Additional populations from Arizona have since been collected and are currently being tested to provide a more comprehensive understanding of insecticide susceptibility across the region.
In the laboratory, larvae were exposed to insecticides at the highest labeled field rate using a leaf-dip bioassay. The insecticides evaluated included Exirel®, Coragen®, Radiant®, Baythroid® XL, Proclaim®, IncipioTM, DiPel®, and XenTari®, representing commonly used conventional and organic management options, as well as IncipioTM, which was recently registered. These laboratory bioassays measure relative susceptibility under controlled conditions using field-collected populations reared in the laboratory. Results represent mortality at the maximum labeled rate under leaf-dip assay conditions and may not directly reflect field performance, where environmental conditions, application timing, coverage, larval stage, and population dynamics influence control. These data are intended to monitor susceptibility trends and help inform resistance management decisions. Accordingly, extrapolation to field performance should be made cautiously, recognizing both the constraints of laboratory bioassays and the mosaic of susceptibility that may exist within and among field populations.
Several Insecticides Showed High Laboratory Mortality Across Field-Collected Populations
Several of the insecticides evaluated caused high mortality of DBM larvae in laboratory assays across field populations. Proclaim, Incipio, Radiant, DiPel, and XenTari caused high mortality, indicating laboratory susceptibility across the tested populations. These products remain promising options for managing DBM in Brassica crops based on current laboratory susceptibility data.
In contrast, Coragen, Exirel, and Baythroid XL resulted in lower mortality in laboratory assays than the other insecticides (Figure 1).
Figure 1. Mean mortality (%) of DBM larvae exposed to the maximum label rate of
insecticides, combined across all six field populations from California and
Arizona.
Consistent Laboratory Mortality Across Regions, with Some Population-Level Variability
The levels of larval mortality caused by each evaluated insecticide were generally consistent across populations collected from major Brassica-growing regions, including Salinas Valley, CA; multiple sites in Coachella Valley, CA; and Gila Valley, AZ (Figure 2). Proclaim, Incipio, Radiant, DiPel, and XenTari resulted in high larval mortality under laboratory assay conditions for most DBM populations tested. However, slight reductions in larval mortality were observed in specific populations. For example, DiPel resulted in approximately 70% larval mortality in the Coachella Valley, CA population # 4, and Radiant caused approximately 55% larval mortality in the Coachella Valley, CA population #2. Despite this variability, these insecticides generally resulted in high mortality of DBM larvae across geographic locations under laboratory assay conditions (see Figure 1). In contrast, Coragen, Exirel, and Baythroid XL resulted in high larval mortality for the laboratory strain but consistently resulted in low DBM larvae mortality in the field-collected populations from Salinas Valley, CA; Coachella Valley, CA; and Gila Valley, AZ (Figure 2).
The reduced and variable levels of larval mortality observed in laboratory assays across multiple field populations for some tested insecticides highlight the importance of routine susceptibility monitoring to better understand resistance dynamics and to support informed field-level decisions regarding product selection and rotation.
Figure 2. Mortality (%) of DBM larvae from laboratory and field populations
exposed to maximum label rates of insecticides.
Key Laboratory Findings
Implications for Resistance Monitoring and Field Decision-Making
Laboratory monitoring informs our understanding of resistance trends, but field scouting remains essential to evaluate how populations respond under production conditions. As always, when in doubt, scout!
Additional Reading Materials
1. Calvin W., M. N. Keith, and B. McGrew. 2025. Guidelines for Effective Management of Diamondback Moth in Brassica Crops. University of Arizona Extension Publication. az2143. https://extension.arizona.edu/publication/guidelines-effective-management-diamondback-moth-brassica-crops
2. Calvin, W. and J. C. Palumbo. 2024. Chlorantraniliprole Resistance Associated with Diamondback Moth (Lepidoptera: Plutellidae) Outbreaks in Arizona Brassica Crops. Journal of Economic Entomology. toae212, https://doi.org/10.1093/jee/toae212.
Relative humidity (RH) is a microclimate variable that strongly shapes crop water relations, canopy wetness duration, and the “comfort zone” for many pests and pathogens. In leafy greens, RH influences transpiration rate, stomatal behavior, and leaf-surface wetness, which are tightly linked to crop stress and disease favorability. Using the AZMET Yuma Valley station annual summaries (1987–2025), our figures show that maximum, minimum, and average RH have declined over time, even though year-to-year variability remains evident.
In Figure 1 (maximum RH), the trendline equation is y = −0.099x + 27.1 with R² = 0.11. The negative slope indicates a gradual decline in annual maximum RH at approximately −0.099 percentage points per year (about −0.99% per decade). The yellow dotted line represents the long-term mean for the series, providing a visual reference for how many years fall above or below the multi-decadal baseline.
In Figure 2 (minimum RH), the trendline equation is y = −0.12x + 24.9 with R² = 0.33. This is the strongest RH signal among the three metrics, indicating that annual minimum RH has decreased at roughly −0.12 percentage points per year (about −1.2% per decade). The higher R² value suggests that the drying signal is more consistently expressed in the minimum RH metric, which is often closely tied to the driest parts of the diurnal cycle and evaporative demand.
In Figure 3 (average RH), the trendline is y = −0.13x + 28.2 with R² = 0.21, indicating a decline in annual average RH of about −0.13 percentage points per year (approximately −1.3% per decade). As in the other figures, the yellow dotted line marks the long-term mean, illustrating that recent years more frequently sit at or below the historical baseline.
What this means for leafy greens agronomy
A gradual decline in RH generally implies higher atmospheric demand for water (a drier air mass), which can increase crop transpiration and intensify the need for precise irrigation management. For leafy greens, this can translate into:
What this means for IPM
Declining ambient relative humidity in the AZMET Yuma Valley record suggests the background atmosphere is gradually becoming drier, which typically corresponds to higher evaporative demand. For IPM in leafy greens, this should be interpreted cautiously: many foliar diseases are favored by extended leaf wetness and high canopy humidity, so fewer naturally humid periods may slightly reduce baseline favorability. However, in irrigated systems the conditions that matter most for infection—irrigation method and timing, canopy density, and short-term weather events—can still create localized humid microclimates and wet leaves even when ambient RH is trending downward. Likewise, lower RH combined with warm conditions can increase the likelihood of transient crop water stress if irrigation is not well aligned with demand, which can indirectly affect pest dynamics and tighten scouting and management windows. Overall, the long-term RH decline is best viewed as a shift toward greater atmospheric drying power, while day-to-day IPM risk remains primarily governed by crop stage, irrigation practices, canopy microclimate, and episodic weather rather than the trend alone.
Figure 1. Distribution and long-term trend in annual maximum relative humidity
(RHmax) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–2025; the
dashed line shows the linear trend and the yellow dotted line indicates the long-term
mean.
Figure 2. Distribution and long-term trend in annual minimum relative humidity
(RHmin) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–2025; the
dashed line shows the linear trend and the yellow dotted line indicates the long-term
mean.
Figure 3. Distribution and long-term trend in annual average relative humidity
(RHavg) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–2025; the
dashed line shows the linear trend and the yellow dotted line indicates the long-term
mean.
VegIPM Update Vol. 17, Num. 10
May 13, 2026
Results of sticky trap catches below!!
Whitefly: Adult activity continues to increase across locations, about average for this time of year. Expect numbers to continue increasing as temperatures warm up.
Thrips: Adult thrips activity increased across locations over the last two weeks. Historically, western flower thrips numbers peak in May.
