The Mexican area-wide trapping network is active at 15 locations across Mexicali and Sonora (Fig 1), giving us an early look at pest activity. Reporting frequency varies among sites, and sticky trap data for aphids, thrips, whiteflies, and leafminers are still being compiled, but these numbers offer a useful regional snapshot.

So far, diamondback moth (DBM) has shown the most ups and downs, while cabbage looper, beet armyworm, and corn earworm remain fairly low (Fig 2).

It’s still early, and the picture will get clearer as more data come in. The real value of the network is watching trends over time; the idea is to see what’s coming our way so we’re not reacting after it’s already here.

Most importantly, this work wouldn’t be possible without the cooperation and effort of our Mexican collaborators who help deploy, collect, and report from the field. We truly couldn’t do this without them, and we’re grateful for the partnership.

 

At the Veg IPM session at Southwest Ag Summit, I’ll share how we’re carrying this trapping network tradition forward, modernizing it and integrating it with new projects and data to strengthen IPM decision-making.

 

Session details below:

AFTERNOON BREAKOUT SESSION

Thursday, February 19, 2026 | 1:30 PM – 3:30 PM

Vegetable IPM

• Dr. Palumbo Veg IPM Insecticide Program: 2025–2026 Efficacy trials — Dr. Samuel Discua Duarte, Yuma Ag Center
• Insecticide Options for Insect Pest Management in Organic Vegetable Production — Dr. Wilfrid Calvin, UofA
• Area Wide Trapping Network: Program Update and Expansion — Macey Keith, UofA
• Advances in Vegetable Weed Management: Herbicides and Chemigation Strategies — Dr. Mazin Saber, UofA

 

*AZ and CA DPR CEUs have been approved for the Southwest Ag Summit. Check the agenda for what CEUs each breakout session offers. 

Figure 1. Locations of 15 pheromone traps across Mexicali and Sonora used to
monitor regional Lepidopteran pests. Orange circles mark each site and its trap
number.


Figure 2. Early-season pheromone trap averages (insects per trap per day)
across 15 Mexican trapping network locations. Diamondback moth has shown the
most variability, while other Lepidopteran pests remain low. 

In the previous edition of this publication, I described the work of Norman Borlaug and his colleagues at the International Maize and Wheat Improvement Center (CIMMYT), whose development of high-yielding wheat varieties helped launch what became known as the Green Revolution. Beginning in the 1940s, Borlaug's breeding program in Mexico produced semidwarf, disease-resistant wheat varieties. These varieties dramatically increased wheat production and improved food security in countries such as Mexico, India, and Pakistan (Britannica 2026).

Although the term Green Revolution remains widely accepted, some historians and environmentalists argue that it should also be viewed as a “Blue Revolution” because of its heavy dependence on irrigation and water resources. The new wheat varieties developed by Borlaug and his CIMMYT colleagues that responded exceptionally well to fertilizer and irrigation.  

Critics contend that the productivity gains associated with Borlaug's varieties required increased use of fertilizers, pesticides, mechanization, and irrigation, particularly in arid and semi-arid regions. In areas such as the Indo-Gangetic Plains, the full benefits of the new wheat varieties could only be realized where reliable irrigation systems existed.

This perspective contends that water management was as important as plant genetics in achieving the dramatic yield increases of the Green Revolution. Some analysts therefore argue that the revolution was both “green,” because of increased plant growth, and “blue,” because of the essential role of water.

There is some validity to this interpretation. The Green Revolution greatly increased food production and is credited with helping prevent widespread famine, saving at least one million lives. But it also accelerated groundwater extraction in several major agricultural regions. Largescale irrigation projects associated with Green Revolution agriculture have been linked to declining groundwater levels and increased pressure on water resources (Britannica 2026).

From an agronomic perspective, however, crop yield reflects the interaction of genetics, environment, and management. The semi-dwarf wheat varieties developed by Borlaug and CIMMYT represented a fundamental advance in genetic yield potential and harvest index (the proportion of plant material directed into the grain versus the vegetative portions of the plant). Prior to these developments, additional water or fertilizer often produced only modest gains because traditional varieties were prone to lodging and disease. The new germplasm changed the crop’s biological capacity to convert resources into grain (improved harvest index).

Crop productivity depends on four key factors:

1. The capture of solar energy through photosynthesis,  
2. adequate water supply,  
3. nutrient availability (primarily bio-available nitrogen), and  
4. genetic capacity to convert resources into harvestable yield.  

Water and nutrients support growth, but they do not create new yield potential by themselves. Borlaug’s breakthrough was the development of varieties that used these resources far more efficiently than previous cultivars. Without the genetic improvements, expanded irrigation and fertilizer use would have generated much smaller gains.

Irrigation and fertilizer inputs removed important constraints, allowing the improved varieties to express their genetic potential. A useful analogy is that water and nutrients provided the fuel, while the new genetics provided the engine. Neither could have achieved the same results alone, but the transformative innovation was the genetic improvement that raised the crop’s biological ceiling.

Therefore, the strongest agronomic argument identifies plant genetics as the foundational innovation of the Green Revolution. Irrigation and nitrogen fertilization were indispensable enabling factors, but they did not fundamentally alter the crop’s biological potential.  

The term Green Revolution remains the most accurate description of Borlaug’s achievement, while the “Blue Revolution” interpretation serves as a reminder of the critical role of water in realizing the benefits of improved crop genetics.

 

References
Britannica. 2026. Green revolution. Encyclopedia Britannica. Available at: https://www.britannica.com/event/green-revolution. Accessed 29 May 2026.

Evenson, R.E., and D. Gollin. 2003. Assessing the impact of the Green Revolution, 1960 to 2000. Science 300:758–762.

Green Revolution. 2026. Wikipedia, The Free Encyclopedia. Available at: https://en.wikipedia.org/wiki/Green_Revolution. Accessed 29 May 2026.

On April 30th of this year, the U.S. Environmental Protection Agency (EPA) published document EPA-HQ-OPP-2026-2973-0002 entitled the “Draft Fungicide Strategy to Reduce Exposure of Federally Listed Endangered and Threatened Species and Designated Critical Habitats from the Use of Conventional Agricultural Fungicides”. This strategy is officially open for public comment through July 20th, and the Arizona Pest Management Center and the University of Arizona are working on formulating a cohesive response.  

This latest draft strategy includes a sizable focus on potential off-site movement of fungicides through runoff associated with treated seed. The following excerpt is taken directly from the document:

“As part of the next steps, EPA is requesting stakeholder input on several aspects of the strategy including… Considerations regarding seed treatments, including seed treatment usage data, information and data on the availability of pesticides on the seed coat to runoff, prevalence of non-commercial (e.g., on-farm, on-site) seed treatments, effects of handling (e.g., loading, planting) on the quality of the pesticide coat and its availability for runoff, and relevant agronomic practices that might reduce the potential for runoff from treated seeds (e.g., seeding depths, disposal)”

Accessible as of June 2026 at https://www.regulations.gov/document/EPA-HQ-OPP-2026-29730002

While the potential route of contaminated off-site runoff from treated seed has been a minor discussion in the scientific literature, it has not been enough of a focus to warrant surveying or regulatory decisions at the federal level thus far. This request for information suggests that this may potentially change going forward. The public comment period presents the best opportunity to bring up practical considerations during early stages before regulatory decisions are made. Regulatory decisions are less likely to present unintended consequences when they are informed by real-world operational perspectives which are ultimately guided by region- and crop-specific experience.

To better inform our response, we are seeking information from across Yuma County to help identify use patterns and current stewardship practices related to fungicide-treated seed. A brief, anonymous, five-minute survey can be found at the following link:

https://uarizona.co1.qualtrics.com/jfe/form/SV_bQpJQzNodI3c5x4

We invite growers, PCAs, seed industry professionals, and distributors to fill it out. If you do not work with treated seed as a grower or PCA, answering the first question will accordingly finish the survey. The response will still provide valuable insight into usage patterns. Thank you in advance for your time and participation. 

It is with mixed emotions that I write to inform you that this will be my last University of Arizona Vegetable IPM Update. The reason – I am retiring. Thank you for your support over the years. It’s been an honor and a privilege working with you and serving this ag community.

Figure 1. Automated Thinning & Weeding Technologies Field Day.
(Photo credits: Rosa Bevington)

Last year, I was contacted by one of our PCAs regarding a concerning observation of escaped Palmer amaranth plants in a cotton field that may indicate potential glyphosate resistance.  

Palmer amaranth continues to be one of the most problematic weeds in row crops due to its aggressive growth habit, high seed production, and documented ability to evolve herbicide resistance.

Field Observation & Seed Collection
Following the PCA report, I visited the field and began collecting seeds from the suspected escaped Palmer amaranth plants during the 2025 cotton growing season.

Sampling collection of Palmer Amaranth, August 18th, 2025

Research Effort and Funding
In collaboration with other colleagues, we submitted a grant proposal aimed at supporting a structured study of Palmer seed collection and greenhouse bioassays to test herbicide response across Yuma and Pinal County locations to map for resistance. Unfortunately, the proposal was not funded. Despite this setback, I decided to move forward by self-funding a preliminary experiment to begin generating data and insights.

Greenhouse Bioassay Initiation
The collected Palmer amaranth seeds were planted on June 4th, 2026, in a greenhouse setting. The initial germination rate of the collected seeds was 77%

Greenhouse Bioassay Experiment Setting

Experimental Plan
The next phase of this experiment involves:

• Thinning the trays to maintain a manageable number of healthy plants per replicate
• Applying multiple rates of glyphosate, including labeled and above-label rates, to assess plant survival and response
• Monitoring plant injury, survival, and potential recovery post-application

This dose-response approach will help determine whether the population exhibits traits consistent with glyphosate resistance.

Field & Greenhouse Documentation
This study will be accompanied by images documenting the process, including:

• Early-stage germination and seedling development in the greenhouse
• Plant responses following herbicide treatment

What’s Next
The plants will continue to be carefully monitored as they develop to an appropriate stage for spraying. Once herbicide applications are completed and responses evaluated, results will be compiled and shared.

Stay tuned for updates as we assess whether this Palmer amaranth population represents a new case of glyphosate resistance in our region. If you have encountered similar escapes or suspect resistance in your fields, please feel free to reach out. Collaboration is key to staying ahead of herbicide resistance challenges

The sweet potato whitefly (Bemisia tabaci) remains one of the most important insect pests affecting melon and vegetable production in the desert Southwest. In addition to causing direct feeding damage, whiteflies transmit economically important viruses, including Cucurbit Yellow Stunting Disorder Virus (CYSDV) and Cucurbit Chlorotic Yellows Virus (CCYV), which can significantly reduce melon yield and fruit quality. Unusually mild winter and abundant weed growth have led to elevated whitefly populations in spring melons and summer cotton. These conditions have allowed whiteflies and associated viruses to survive and build up earlier than typically observed in the region. Therefore, whitefly and virus pressure are also expected to be higher than normal this fall.  

Whiteflies reproduce on numerous crops and weed hosts throughout the year. Cotton, alfalfa, melons, cucurbits, lettuce, and several weed species serve as important reservoirs that sustain populations between cropping cycles. As cotton and other summer hosts mature or are terminated, adult whiteflies disperse into newly planted fall melons, often bringing virus inoculum with them.

Management
Successful whitefly management requires an integrated approach that begins before planting and continues throughout the season. Relying solely on insecticides is rarely sufficient and can accelerate resistance development. Instead, effective programs combine resistant variety, crop health, sanitation, crop placement, scouting, biological control conservation, physical control, and responsible insecticide use.

Sanitation: Sanitation remains the most important management practice for reducing both whitefly populations and virus sources. Crop residues should be destroyed immediately following harvest, and volunteer melons, volunteer cotton, and weed hosts should be eliminated whenever possible. Maintaining clean field borders, canal banks, roadsides, and fallow areas helps reduce whitefly breeding sites and virus reservoirs. Area-wide cooperation among neighboring growers greatly improves the effectiveness of sanitation efforts.

Crop placement/Isolation: Field location can also influence whitefly pressure and virus incidence. Whenever possible, fall melon fields should be planted away from spring melon production areas and major whitefly sources such as cotton and alfalfa. Research conducted in Arizona has consistently shown that melon fields located near these crops are at greater risk of whitefly infestation and CYSDV infection. Isolation distances of 1.2 miles for cotton, 1.9 miles for spring melon fields with volunteers, and 0.6 mile for spring melon fields without volunteers are recommended.

Crop health: Maintaining healthy, vigorously growing crops can help reduce the impact of whitefly feeding and virus infection. Proper irrigation management, balanced fertility programs, and avoidance of excessive nitrogen applications can reduce plant stress and improve crop tolerance. Excessive vegetative growth resulting from over-fertilization may increase crop attractiveness to whiteflies.

Physical control: Row covers can provide effective protection against early-season whitefly infestations and virus transmission in melon production. Covers should be installed before crop emergence and removed before flowering to allow pollination. In areas with high migration pressure, an insecticide application following row-cover removal may be warranted.

Scouting: Regular scouting is essential for timely management decisions. Fields should be monitored beginning at crop emergence and inspected at least weekly throughout the season. Particular attention should be given to fields located near cotton, alfalfa, or recently harvested crops where whitefly movement is likely. Monitoring should include assessments of adult whiteflies, immature stages, virus symptoms, and beneficial insect activity.

Conservation of natural enemies: Natural enemies can contribute to whitefly suppression and should be conserved whenever possible. Predators such as lacewings, lady beetles, minute pirate bugs, and big-eyed bugs, along with some parasitoid wasps, help suppress whitefly populations. Although biological control alone may not prevent economic damage during heavy infestations, preserving beneficial insects can reduce whitefly pressure and improve overall pest management.

Insecticide control (conventional): In conventional production systems, whitefly management should begin at planting with systemic insecticides that protect young seedlings during the critical establishment period when plants are most vulnerable to virus infection. Products such as Verimark, Sivanto, Venom, Scorpion, and imidacloprid-based materials can provide early protection. During crop development, foliar products including PQZ, Sefina, Sivanto, Assail, Exirel, and Beleaf can be used to suppress migrating adults. Effective rotation among modes of action is essential for preserving product performance.

Insecticide control (organic): Organic production systems rely heavily on resistant varieties and preventative measures such as sanitation, crop isolation, weed management, and conservation of beneficial insects. Organic insecticides, including Pyganic, neem-based products, insecticidal soaps, and microbial products containing Beauveria bassiana (BotaniGard) or Isaria fumosorosea (PFR-97), can provide suppression when applied early and with thorough coverage. However, these products generally have limited residual activity and are most effective when used before populations become established.

Pollinator protection: Pollinator protection should remain a priority in melon production. Honeybees are essential for fruit set and yield. Whenever possible, insecticide applications should be avoided during bloom. If treatments are necessary, applications should be made during evening or nighttime hours when bees are not actively foraging.

Insecticide resistance management: Because whiteflies readily develop resistance to insecticides, resistance management should be incorporated into every control program. Insecticides should be rotated among different IRAC mode of action (MoA) groups, and repeated applications of products with the same MoA should be avoided. Treatment decisions should be based on field scouting and pest pressure rather than calendar schedules.

Conclusion
Given the elevated whitefly populations and virus incidence observed this spring, growers should anticipate increased whitefly and virus pressure during the upcoming fall season. Implementing an integrated management program that emphasizes resistant varieties, crop health, sanitation, crop placement, scouting, conservation of biological controls, physical controls, and responsible insecticide use will provide the best opportunity to minimize economic losses and protect crop productivity.

Additional Documents for More Detailed Information and Control Options

Palumbo J.C. 2020. Cultural Practices Key to Whitefly and Virus Management in Fall Melons.http://hdl.handle.net/10150/677934

Palumbo J.C. 2024. 2024 Guidelines for Whitefly / CYSDV Management on Fall Melons. http://hdl.handle.net/10150/677911

Following my recent article on Vapor Pressure Deficit (VPD), I received four thoughtful questions from colleagues in Arizona and California. While each question approached the topic from a different perspective, all pointed to a broader concept: the role of crop microclimates in shaping plant growth, water use, and plant health. This article takes a closer look at crop microclimates and why they matter in agricultural production systems. However, the conditions measured by a weather station (Figure 1) may not be identical to those experienced within a crop canopy. The environment surrounding leaves is often referred to as the crop microclimate. 

Figure 1. The Arizona Meteorological Network (AZMET) weather station at the Yuma Valley Agricultural Center. Weather stations provide standardized measurements of ambient environmental conditions; however, environmental conditions within crop canopies may differ from those measured at the station, creating crop-specific microclimates.

As crops grow and develop, they can modify the environment within the canopy by intercepting sunlight, shading the soil, and influencing temperature, humidity, and air movement around the plant. Crop architecture, canopy density, growth stage, irrigation practices, and soil moisture conditions can all contribute to these microclimatic differences. Understanding crop microclimates is important because plants respond to the conditions they experience rather than solely to the conditions measured above the canopy. Environmental factors such as temperature and humidity influence plant growth, transpiration, and physiological processes. Likewise, many plant diseases are affected by conditions within the canopy, including temperature, humidity, and the presence of moisture on plant surfaces. Weather-station measurements remain extremely valuable because they provide a consistent and standardized description of environmental conditions. At the same time, understanding crop microclimates may provide additional insight into crop responses, water use, and plant health.

Many questions remain regarding how environmental conditions measured by weather stations relate to those experienced within different crop canopies and under different management practices. Continued research will help improve our understanding of these relationships and their implications for irrigation management, crop performance, and disease development. The recent discussions generated by the VPD article highlight the importance of considering both the broader environment measured by weather stations and the microenvironment experienced by plants. Together, these perspectives can help us better understand the complex interactions among crops, management practices, and environmental conditions. 

VegIPM Update Vol. 17, Num. 12
June 10, 2026

Results of sticky trap catches below!!

 

Whitefly: Adult activity has increased significantly across locations; above average for this time of the year. Historically, whitefly numbers peak in July.  

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