Norman E. Borlaug completed his Ph.D. in plant pathology at the University of Minnesota in 1942. He worked briefly as a microbiologist for the DuPont de Nemours Foundation. In 1944 he accepted a position as a geneticist and plant pathologist and began work at the International Maize and Wheat Improvement Center (CIMMYT, Centro Internacional de Mejoramiento de Maíz y Trigo) based in Ciudad Obregón, Sonora, Mexico.
Norman Borlaug (left) and his colleague George Harrar in a wheat field in the Yaqui Valley, Sonora, Mexico in 1944.
In joining CIMMYT, Borlaug had the responsibility of organizing and directing the Cooperative Wheat Research and Production Program in Mexico, which was a joint program with the Mexican government & Rockefeller Foundation. This program utilized scientific research in a fully integrated agronomic system utilizing genetics, plant breeding, plant pathology, entomology, soil science, and cereal technology.
The primary objective of Borlaug and his team of colleagues was the development of semi-dwarf varieties of wheat with improved disease resistance, particularly stem rust caused by Puccinia graminis f. sp. tritici (Borlaug, 1968). In the 1940s, Mexico imported a substantial portion of its wheat because of low productivity and severe disease pressure. Within twenty years Borlaug and his team were realizing spectacular success in developing high-yielding short-strawed, diseaseresistant wheat varieties.
One of the key developments by Borlaug and his colleagues was a breeding strategy that combined shuttle breeding between contrasting environments, in this case of the Yaqui Valley of Sonora near Ciudad Obregón, Sonora and Puebla, Mexico with rigorous disease screening. This approach accelerated genetic gains and produced broadly adapted wheat cultivars with durable disease resistance.
Borlaug’s team also developed the incorporation of dwarfing genes into spring wheat varieties. Traditional wheat cultivars commonly developed long stalks and tall plants that were prone to lodging, particularly if provided sufficient water and nitrogen (N) fertilization. This lodging and vegetative growth tendency was limiting yield potential. The new semi-dwarf cultivars allocated more biomass to grain production with a higher harvest index (Pingali, 2012).
The release of two principal varieties, Lerma Rojo 64 and Sonora 64, dramatically increased yields in Mexico and by 1963, Mexico became a net exporter of wheat. Borlaug and the CIMMYT program next directed attention to wheat production in southern Asia and between 1965 to 1970, wheat yields nearly doubled in Pakistan and India, greatly improving food security.
The collective increases in yield from these programs have been labeled the “Green Revolution”, referring to the rapid increase in global agricultural productivity that occurred between the 1940s and the 1970s through the development of improved crop varieties. These developments were especially important in Asia and Latin America, where food shortages and rapid population growth raised concerns regarding widespread famine (Evenson and Gollin, 2003).
The Green Revolution is often credited with saving over a billion people from starvation and in 1970 Borlaug was Awarded the Nobel Peace Prize in recognition of his contributions to world peace through increasing food supply. He is the first and only agronomist to win the Nobel Peace Prize.
The program was a systems approach that consisted of agronomic practices that included improved irrigation, fertilization, and mechanization. Although many scientists, governments, and institutions contributed to the Green Revolution, the work of Norman Borlaug was central to its success.
The Green Revolution developments were also extended beyond wheat. Similar advances occurred in rice breeding through the development of semi-dwarf rice cultivars such as IR8 at the International Rice Research Institute. These plant breeding innovations have contributed to major increases in cereal grains and other crops across many parts of the world in the past 50 years (Khush, 2001).
Borlaug repeatedly and quite emphatically pointed out the fact that their work with the CIMMYT program was only one small step, and it was far from perfect. He consistently encouraged the next generation of agronomists and agricultural scientists to continue working diligently to address food security in the fight against what he often referred to as the “population monster” facing humanity.
Borlaug and the CIMMYT program substantially reduced hunger and demonstrated the importance of science-based agricultural innovation. Due to his contributions to global food security, Borlaug remains widely recognized as one of the most influential agronomists and plant breeders of the twentieth century.
References
Borlaug, N.E. 1968. Wheat breeding and its impact on world food supply. Proc. Third Int. Wheat Genet. Symp. 1:1–36.
Evenson, R.E., and D. Gollin. 2003. Assessing the impact of the Green Revolution, 1960 to 2000. Science 300:758–762. doi:10.1126/science.1078710.
Khush, G.S. 2001. Green revolution: The way forward. Nat. Rev. Genet. 2:815–822. doi:10.1038/35093585.
Pingali, P.L. 2012. Green Revolution: Impacts, limits, and the path ahead. Proc. Natl. Acad. Sci. USA 109:12302–12308. doi:10.1073/pnas.0912953109.
Few things in Yuma County are more frustrating than watching lettuce wilt in the field. Even the best-managed fields are not immune to the many destructive soilborne pathogens capable of causing significant economic losses in lettuce production fields.
It is an unfortunate reality that Fusarium wilt, corky root, bottom rot, and lettuce drop are encountered and require management nearly every season in Yuma to produce a healthy crop. Although advances in resistant cultivars and integrated disease
management have improved our ability to reduce some of the crop losses to these diseases, management options for soilborne diseases, in general, remain severely limited and often are ineffective once symptoms progress to root or crown rot and irreversible
wilting. Strong, durable genetic resistance remains the strategic priority and most viable option when it comes to the management of these pathogens.
To select the right genetic resistance package, accurate field history and proper diagnosis of the cause of plant health challenges on that ground is critical. One of the greatest obstacles in plant disease diagnosis is that symptoms alone are rarely
what we call pathognomonic, that is, they are seldom unique enough to identify down to a single disease or environmental stressor. Temperature, soil moisture, plant age at time of infection, and varietal susceptibility all influence how diseases and
disorders develop and how symptoms are expressed in the plant as a response. As a result, the same pathogen can produce different symptoms under different conditions, while entirely different pathogens may produce nearly identical symptoms. Add to
this the complexity of the frequent occurrence of co-infections with multiple pathogens colonizing the same host at the same time and the ability to provide field diagnoses or diagnosis from pictures can quickly become confusing, overwhelming, or
downright impossible.
This known variability in symptom expression underscores the importance of confirming a diagnosis rather than relying solely on field observations, especially when the time comes for selecting resistant varieties to be planted in fields with a history
of soilborne diseases. Ideally, lettuce shouldn’t be planted on ground that is contaminated with soilborne pathogens, but this isn’t always feasible in our production systems.
Despite my obligatory warning for the difficulty and unreliability of diagnosing plant diseases and disorders from symptoms alone, I thought it would be a good chance to highlight a few key trends for two infamous diseases that we frequently observed
during last season’s atypically warm and rainy weather. I’m talking of course about Fusarium wilt and corky root. My hope is that these observations may prove helpful when scouting wilting fields, explaining your observations, and, importantly,
making it easier to document on our submission sheet what you’re seeing in the field if you choose to drop off samples to the clinic for culture testing and confirmation diagnoses. Of course, I remain happy to take a look and sample from the
symptomatic field as well. Over the 2025-2026 season the plant clinic received 20 samples culturing positive for Fusarium wilt, 16 for corky root, and 8 for a co-infection with both pathogens simultaneously.
In the field, the two diseases often appear indistinguishable from aboveground symptoms alone. Both commonly produce wilting, which may be more pronounced particularly during the heat of the day then seemingly “recover” in the evenings. Plants often lose their characteristic healthy, green waxy luster and instead develop a dull, matted appearance that is more apparent when compared with neighboring healthy plants or fields and as the wilting intensifies. As the diseases progress, the outermost leaves surrounding the crown may rot and collapse, further contributing to the appearance of a sick and declining plant. At this point, secondary microorganisms of both the bacterial and fungal kind may set in and produce signs of growth as they feed on the dead tissue, potentially appearing to be related to the cause of the disease and complicating diagnosis.
Below ground, corky root primarily affects the outermost tissues of the root system, causing feeder roots and the taproot to develop yellow to brown (sometime with specks of green) lesions that eventually crack and become roughened. To me, severely affected roots appear as if they are covered in mesquite bark. In contrast, Fusarium wilt primarily invades the plant's vascular system. Although root deterioration may occur (especially on small feeder roots), the hallmark of Fusarium wilt is vascular discoloration within the taproot and crown, where the water-conducting xylem tissues become tan to reddish-brown. These belowground differences, together with laboratory culture or other laboratory testing, provide the evidence needed to confidently distinguish between the two diseases.
Figure 1: Symptoms on a sample culturing positive for Fusarium wilt alone. Left.) outside view of the root system mostly absent of any rot symptoms, and right.) dissected root showing interior vascular discoloration. Note the bright white cortical tissue between the vascular tissue (center) and epidermis (outermost layer of cells, the “skin”) and near absence of overall rot of inner taproot tissue that is commonly observed with other soilborne diseases. The vascular system appears reddish due to the colonization with Fusarium oxysporum f. sp. lactucae.
Figure 3: Symptoms on a sample co-infected with Fusarium wilt and corky root. Left.) outside view of the root system showing significant barky lesions, and right.) dissected root shows a barky vascular dry rot towards the tip of the taproot with reddish-brown discoloration moving up towards the crown.
The images above are from some of the more diagnostically clear samples we have received in the clinic. As mentioned earlier, timing of infection, local microclimate, and varietal genetics can play a huge role in defining how a plant expresses disease
symptoms, so these observations of textbook symptomology may not be as clear in every field with wilting that you manage. For these reasons, laboratory testing remains the gold standard for disease diagnosis. Submission of symptomatic plants to the
diagnostic clinic allows for pathogen isolation and culture, providing definitive identification that can distinguish between diseases with similar symptoms. Accurate diagnosis is the foundation of effective disease management, ensuring that control
measures are directed at the true causal agent rather than its look-alikes. The Yuma Plant Health Clinic is here to help to that end.
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
Weed control in wheat and barley in the Southwestern United States faces significant challenges, including high winter temperatures, extensive irrigation, and limited crop rotation options. Although wheat and barley are naturally competitive crops, research indicates that weeds can reduce yields, hinder harvesting, increase grain impurities, cause grain discoloration, and lead to insect or mold problems during storage if not managed effectively.
An Integrated Pest Management (IPM) approach—which combines prevention, cultural practices, and the appropriate use of herbicides—offers the most sustainable and reliable weed control within wheat production systems in low-desert regions.
Focus on Early Control
Weeds that emerge simultaneously with the wheat crop, or shortly thereafter, cause the greatest yield losses. Weed species typically include annual ryegrass, wild oats, Italian ryegrass, Canarygrass species, London rocket, various mustard species, and Fiddleneck. Fields should be free of weeds at the time of planting and must be kept clean until the onset of the tillering stage.
Cultural Practices Remain Essential
Recommended Herbicide Programs (Examples of Options)
Note: Always follow the instructions on the product label specifically for your state, wheat variety, soil type, and growth stage. The rates listed below reflect ranges commonly used in the Southwestern United States.
OR
OR
OR
Resistance and Integrated Pest Management (IPM) Considerations
Rotate the use of multiple effective herbicides.
Recommended Reading
Growers and PCAs are strongly encouraged to review the following foundational reference guide for additional details regarding weed biology, application timing, and appropriate herbicide options for Arizona’s low deserts:
Bottom Line
Successful weed management in wheat and barley crops across the Southwestern United States relies on early-season management, high crop competitiveness, and the timely and appropriate application of herbicides. Integrating extension-based cultural practices with weed management programs that are mindful of herbicide resistance remains the most effective strategy for safeguarding both crop yield and grain quality.
Extension Support and Collaboration
I am more than happy to conduct field visits, assist with weed identification and management decisions, or collaborate on herbicide efficacy trials targeting weed problems in wheat and barley. Please feel free to reach out to discuss on-farm visits or research opportunities.
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.
In the laboratory, larvae were exposed to insecticides at the highest labeled field rate using a leafdip bioassay. The insecticides evaluated included Exirel®, Coragen®, Harvanta®, Radiant®, Baythroid® XL, Proclaim®, Torac®, 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 10 field populations from California and Arizona.
DBM Mortality by Collection Location, with Some Population-Level Variability
The levels of larval mortality caused by each evaluated insecticide were generally consistent across populations. For DBM populations collected during fall 2025, Proclaim, Incipio, Radiant, DiPel, and XenTari resulted in high larval mortality under laboratory assay conditions for most DBM populations tested (Figure 2). 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 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).
We observed similar mortality trends among populations collected during winter/spring 2026 for the evaluated insecticides except for DBM mortality caused by Dipel, which declined in many populations (Figures 3 and 4). Harvanta was evaluated for two populations (Imperial Valley, CA and Somerton, AZ), which exhibited similar reduced larval mortality to that of the other diamides. Torac was also evaluated for the Imperial Valley, CA, population, resulting in a high level of DBM mortality (Figure 4). We also tested a population collected from the Yuma Ag Center, which resulted in susceptibility levels very similar to those of the susceptible laboratory colony (Figure 3). Previous DBM monitoring studies performed by Dr. Palumbo over several years also showed that while populations collected from commercial fields showed very low susceptibility to diamides, populations collected at the Yuma Ag Center remained highly susceptible. This indicates that transplant sources and/or field-specific DBM management practices are also affecting DBM susceptibility and control across Arizona’s brassica-growing regions.
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 field populations collected from Arizona
and California as affected by maximum label rates of 8 insecticides, Fall 2025.
Figure 3. Mortality (%) of DBM larvae from a susceptible lab colony and field
populations collected from Arizona as affected by maximum label rates of 8
insecticides, Winter/Spring 2026.
Figure 4. Mortality (%) of DBM larvae from two field populations collected from
Arizona and California as affected by maximum label rates of ten insecticides, Spring 2026.
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
The figure shows a wind rose based on daily wind direction data from the AZMet Yuma Valley station from January 1, 2021, through May 24, 2026. This figure (Figure 1) summarizes where the wind came from most often, not how fast the wind was blowing. Longer bars indicate more frequent wind direction. In this dataset, winds most frequently came from the north–northeast and south–southeast directions, while winds from the east and west occurred less frequently.
Figure 1. Wind rose showing the frequency distribution of daily wind direction at the AZMet Yuma Valley station from January 1, 2021, through May 25, 2026. Longer bars indicate more frequent wind directions. Dominant winds were primarily from the north–northeast and southsoutheast directions. Data source: Arizona Meteorological Network (AZMET) – University of Arizona
Wind direction is important because it indicates the likely origin and pathway of air moving into crop fields. Depending on surrounding land use and regional weather conditions, air moving from different directions may be warmer, cooler, drier, more humid, or dustier. For example, air passing over irrigated agricultural areas may carry relatively more humidity, while air moving across desert, fallow ground, or dry soil surfaces may be hotter, drier, and dustier. Therefore, wind direction can influence field microclimate, soil moisture loss, crop stress, pest movement, and spray drift pathways.
For irrigation management, prevailing wind direction can help growers interpret field variability. In flood or furrow irrigation, wind direction may influence surface drying after irrigation, especially along exposed beds, field borders, and tail-end areas. Wind moving across hot, dry ground can accelerate evaporation from wetted furrow surfaces and contribute to soil crusting. This may affect seedling emergence, salinity accumulation near the bed surface, and the timing of the next irrigation. In sprinkler-irrigated fields, wind direction during irrigation can influence water distribution patterns. In drip-irrigated vegetables, wind direction may help explain recurring dry zones, edge effects, or uneven crop vigor when combined with soil moisture, ET, and field observations.
Wind direction can also affect crop growth and development by modifying canopy microclimate. Air movement from different directions may influence canopy temperature, humidity, dust movement, and drying conditions. Young vegetable seedlings are especially sensitive to windblown soil particles, which can cause abrasion, stand injury, and delayed early growth. Leafy vegetables may also show reduced market quality when exposed to repeated dust or sand movement. This figure does not directly measure crop stress, but it helps identify the directions from which wind-related exposure is most likely to occur.
The wind rose should not be interpreted as direct evidence of yield loss. It only shows the dominant wind direction. However, yield and quality can be affected when prevailing wind direction interacts with high wind speed, dry air, poor irrigation uniformity, soil moisture stress, or physical crop injury. Long-term wind direction information can help growers evaluate whether certain field margins, bed orientations, or crop rows are repeatedly exposed to incoming air movement and associated stress factors.
Wind direction is also important for IPM because it influences the movement of insects, pathogens, dust, and pesticide droplets. Aphids, whiteflies, thrips, leafhoppers, and some airborne pathogens may move with prevailing air currents. Knowing the common upwind directions can help growers identify potential pest-source areas and improve scouting strategies. Wind direction is also important for pesticide applications because it determines the likely pathway of spray drift and off-target movement.
Overall, wind rose information provides a practical decision-support tool for understanding dominant airflow pathways in Yuma vegetable production. This figure should be used together with real-time wind speed, wind direction, pesticide label restrictions, droplet size, boom height, irrigation records, soil moisture monitoring, ET data, and field scouting. When combined with these additional data, wind direction can support better irrigation planning, crop stress interpretation, yield protection, and IPM decision-making.
References: Arizona Meteorological Network (AZMet) https://azmet.arizona.edu/
VegIPM Update Vol. 17, Num. 7
April 1, 2026
Results of pheromone and sticky trap catches below!!
Corn earworm: CEW numbers remained high over the last two weeks; numbers remain high particularly in Welton and Tacna areas. Above average for this time of season.
Beet armyworm: BAW activity remained steady over the last two weeks. Above average for this time of the season. Historically BAW numbers are expected to continue increasing over the next few weeks.
Cabbage looper: Cabbage looper moth activity decreased over the last two weeks but remains higher than average for late-March. Based on historic data, expect to see high numbers through the end of the produce season.
Diamondback moth: Adult activity increased across most locations. High numbers seen in Yuma Valley. About average for this time of the year.
Whitefly: Adult activity increased across all locations, about average for this time of year. Expect numbers to continue increasing as temperatures warm up.
Thrips: Over the last two weeks, thrips adult activity continued to increase across locations and reached season highs. Higher than average for this time of year. Expect numbers to continue increasing as temperatures warm up
Aphids: Winged aphid numbers continue to decrease at most sites in the last two weeks. At our efficacy trials at YAC, most aphids died due to the high temperatures. below average for this time of the year.
Leafminers: Adult leafminer activity remains steady, high numbers continue to be seen in Yuma Valley, about average for this time of the season.
