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:
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.
Fall melon season is approaching, and one recurring question I've been hearing is: Will viruses be as bad this fall as they were in the spring?
The incidence and severity of melon viruses this past spring were unprecedented across Yuma County, Imperial County, and northern Mexico. This is supported by the volume of feedback we received from growers, PCAs, and industry representatives who attended the June 2nd melon virus incident response meeting. As a result, predicting what we can expect is going to happen this fall is difficult. We have no recent, if any, experience with virus pressure at this scale in spring melon to guide our expectations for the upcoming fall season. At this point, predictions are more of an educated guess without the guidance of past observations.
To quickly recap, the three main viruses that affected cucurbits this spring were cucurbit yellow stunting disorder virus (CYSDV), cucurbit chlorotic yellows virus (CCYV), and watermelon chlorotic stunt virus (WmCSV). All three are transmitted by the Biotype B whitefly (Bemisia tabaci), whose populations overwintered at unusually high levels between 2025 and 2026. Between melon seasons, these viruses persist in a wide range of crop and weed hosts, many of which show few or no visible symptoms of infection. Unfortunately, these asymptomatic plants can still serve as reservoirs, allowing both the viruses and their whitefly vectors to bridge the melon-free gap between cropping seasons and provide a source of inoculum for newly planted fields. It is an unfortunate reality that neither the whitefly vectors nor many of the alternate host plants (weeds) show symptoms or suffer ill effects while carrying these viruses. As a result, they can stealthily maintain virus populations between melon seasons and serve as a source of infection for newly planted fields.
Below is a compilation of reported host plants for CYSDV, CCYV, and WmCSV. This list reflects the viruses’ confirmed hosts identified to date but is unlikely to be exhaustive. Additional weed and crop species may also be capable of serving as reservoirs for these viruses but have yet to be discovered or reported. Note that many of these plants may grow throughout the region as weeds, native vegetation, commercial crops, or in backyard gardens:
Table 1: Primary and alternate hosts of CYSDV, CCYV, and WmCSV reported to date.
I can see this upcoming melon season unfolding in one of two ways. On one hand, the most intuitive prediction is that the high virus inoculum and abundant whitefly populations present during the spring melon season will carry over into the fall, resulting in early and significant virus pressure. On the other hand, the intensive whitefly management programs implemented throughout the spring may have suppressed vector populations to provide knockdown to pre-winter 2025 levels, resulting in lower virus incidence early in the season than at the start of spring.
Regardless of which scenario plays out, proactive and preventative management of both whiteflies and weed reservoirs remains the most effective strategy for minimizing virus pressure in fall melons. This approach targets two critical stages of the disease cycle by reducing the initial sources of virus inoculum and limiting the whitefly vectors responsible for further virus spread.
Dr. Palumbo developed a management guide for whiteflies and CYSDV in fall melons in 2024. The recommendations are based on research findings from two key publications and provide practical guidance for reducing virus risk throughout the season, from planting through netted fruit (Castle 2017a and 2017b).
Table 2: Insecticide Use Guidelines for Whitefly /CYSDV Management in Fall Melons
The earlier melons become infected with one or more of these viruses, the greater the impact on plant growth, fruit development, and ultimately yield. Even when infection cannot be completely prevented, delaying virus establishment can substantially reduce losses in both yield and fruit quality. Protecting young plants from early whitefly feeding, and virus infection, is therefore one of the most important management objectives to reducing losses.
In field trials comparing at-plant soil applications of flupyradifurone (trade name Sivanto), dinotefuran (Venom), imidacloprid (Admire Pro), and cyantraniliprole (Verimark), Dr. Palumbo and colleagues found that flupyradifurone and dinotefuran provided the greatest protection against both whiteflies and lowest final incidence of CYSDV (Castle et al. 2017b). All products were applied as a single soil shank injection at planting, allowing systemic uptake and protection during crop establishment.
Across both spring and fall trials, flupyradifurone consistently produced the lowest whitefly densities and the lowest incidence of CYSDV. Dinotefuran was the second most effective treatment, significantly reducing both whitefly populations and CYSDV incidence, although its performance was somewhat less consistent than flupyradifurone. In contrast, at-planting treatment with imidacloprid and cyantraniliprole did not consistently reduce CYSDV incidence.
Further reading:
Castle, S., Palumbo, J., Merten, P., Cowden, C. and Prabhaker, N. (2017a), Effects of foliar and systemic insecticides on whitefly transmission and incidence of cucurbit yellow stunting disorder virus. Pest. Manag. Sci., 73: 1462-1472. https://doi.org/10.1002/ps.4478
Castle, S.J., Palumbo, J.P., Merten, P. (2017b), Field evaluation of cucurbit yellow stunting disorder virus transmission by Bemisia tabaci. Virus Res., 241:220-227. doi: https://doi.org/10.1016/j.virusres.2017.03.017
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
About two weeks ago, we hosted the Automated Thinning & Weeding Technologies Round-Up at the University of Arizona’s Yuma Ag Center, Yuma, AZ (Fig. 1). The field day showcased the latest automated thinning and weeding technologies operating in the field at the commercial field scale level (> 1 acre). Participating companies thinned and/or weeded approximately one half of their respective demo plots 2-3 days prior to the event so that attendees could see the end result of the thinning/weeding “treatment”. The other half of the plot was used for live demonstrations the day of the event.
The performance of all of the thinning machines in the show was impressive, especially given the challenging conditions – intermittent patches of heavy weed pressure and roughly 2” nominal plant spacing with very poor plant spacing uniformity (i.e. a high percentage of the plants were closer than 1” apart) (Fig. 2a-c). I was also very impressed with the precision, speed and efficacy of the high precision spot sprayers and mechanical weeders (Fig. 2d).
If you missed the field day and you would like to see the demonstration plots and evaluate them for yourself, please feel free to contact me. We’ll be keeping the plots intact for the next couple of weeks.
Additionally, you are more than welcome to visit the plots with representatives from the companies that participated in the field day. Please contact me if you are interested. I’d be more than happy to make the arrangements.
Fig. 2. Lettuce plant spacing in the 1-acre plots at the 2025 Automated Thinning &
Weeding Technologies Round-Up was a) tight (< 2”) and non-uniform. Automated
thinning and weeding machines were able to effectively (b) thin the closely spaced
lettuce plants, (c) identify and thin lettuce crop plants to the desired spacing in weedy
conditions and d) deliver herbicidal materials to target weeds precisely without injuring
crop plants.
Palmer amaranth escapes are showing up in cotton despite good early-season control. Most issues are tied to late flushes, missed timing, and heavy reliance on glyphosate programs.
Why escapes are happening
Glyphosate resistance in Palmer is already widespread in the Southwest, so overreliance will continue to fail.
What to do differently
Program basics by system
All cotton systems (foundation)
LibertyLink
XtendFlex / Enlist
Adjuvant reminders
IPM reminders
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/10150/677911Following 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. 14
July 8, 2026
Results of trap catches below!!
Whitefly: Adult activity remains steady across locations; above average for this time of the year. Historically, whitefly numbers peak in July.
Thrips: Adult thrips activity decreased 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.
