This week I presented a poster at the Entomological Society of America’s (ESA) 2025 Annual Meeting in Portland, Oregon, sharing the impacts of Arizona Pest Management Center (APMC) with a diverse audience representing part of the ESA’s nearly 7,000 members nationwide. It was rewarding to share how our real-world IPM efforts in the desert Southwest influence field decisions, grower profitability, and environmental health.

Attendees from other entomological disciplines were surprised by the measurable progress our Arizona vegetable and cotton IPM programs have achieved, flipping the script from risk to safety in how we tell the story of pest management. It was a great reminder of how powerful IPM can be when guided by science and collaboration.

You can find the poster here: Arizona Pest Management Center: Advancing Integrated Pest Management (IPM) for Agriculture and Communities

At the APMC, our approach to resistance management starts with prevention by avoiding resistance before it ever appears. That means rotating modes of action and skipping unnecessary sprays to protect what still works. If you want to learn more (or want a good chuckle) watch our short Proactive Resistance Management App commercial to see how easy proactive can be. Click below to watch the commercial.


To contact Macey Keith go to: maceyw@arizona.edu

Nitrogen (N) is the nutrient required in the largest amount by plants and the most common nutrient needed in crop fertilization. When N fertilizers are applied to a field, they are immediately subject to a myriad of possible reactions and transformations, as described as the N cycle (Figure 1).

Nitrogen is the most abundant element in the atmosphere (approximately 80-82%) as nitrogen gas (N₂) but is inert and not directly usable by most organisms. Thus, atmospheric N gas is not bioavailable. In desert crop production systems, bioavailable N is the second most common limiting factor behind water.

To become bioavailable, N₂ gas in the atmosphere must be converted into different mineral or inorganic forms through a process called nitrogen fixation (Figure 2), which is carried out by specific bacteria, lightning, and industrial processes such as the Haber-Bosch process in commercial fertilizer production (Nevins et al., 2020).  

When N is fixed or transitioned from N₂ gas into inorganic forms such as ammonia (NH₃) and then into ammonium (NH₄⁺) and nitrate (NO₃^-) in the soil, it can then be taken up and utilized by plants, entering the food chain and becoming available to other organisms. Nitrate-N (NO₃^-) is the preferred form for plant uptake (Figure 1).

Nitrogen immobilization is a process in soil systems where soil microbes consume and temporarily convert inorganic nitrogen into organic compounds, making it unavailable for plants. This occurs when decomposing plant material with a high carbon-to-nitrogen (C:N) ratio is added to the soil, as microbes consume the available mineral or inorganic N to break down the carbon-rich organic materials, such as crop residues. The process stops once the residue has decomposed, and the N cycle continues as organic forms are converted and released into the soil as inorganic forms in the soil through mineralization.

Mineralization of soil N is the process of converting organic forms of N into inorganic or mineral forms (Figure 3). 

Figure 1. The nitrogen cycle. Source: Stevenson, 1982.


Figure 2. Nitrogen fixation is the conversion of dinitrogen gas (N₂) to ammonia (NH₃) and can be catalyzed by biotic and abiotic processes. Source: Nevins et al., 2020.

Figure 3. Nitrogen mineralization as organic N is converted or “mineralized” to
ammonium (NH₄⁺) in the soil environment. Source: Nevins et al., 2020. 
 
Nitrification is the process of converting ammoniacal N (NH₄⁺) into nitrite (NO₂^-) and then
into nitrate (NO₃^-). Both steps are carried out by naturally occurring chemoautotrophic
bacterial organisms, Nitrosomonas and Nitrobacter (Figures 4 and 5).



Figure 4. Nitrification is the transformation of ammonium (NH₄⁺) to nitrite (NO₂^-) and then
(NO₃^-) by naturally occurring soil bacterial oxidizing organisms. Source: Nevins et al.,
2020.


Figure 5. The two step process of soil nitrification shows the specific naturally occurring
soil bacterial organisms necessary for the reactions, Nitrosomonas and Nitrobacter.

Nitrogen Mineralization–Immobilization Transformation (MIT) Cycle in Soils

The nitrogen (N) mineralization–immobilization cycle represents the continuous biological transformation process between organic and inorganic forms of N in soil (Figure 6). It is driven primarily by the activity of soil microorganisms that consume mineral (inorganic) N and the those that decompose organic matter.

The MIT cycle represents the core elements of what we are trying to manage in the soils for crop production systems to optimize plant available N and produce healthy crops (Ros, et al, 2011 and Johnson et al., 2007).

Healthy soils are constantly active in these transformation processes. Thus, any inorganic or mineral source of N that is applied to the soil is immediately subject to immobilization and possibly converted into organic forms of N by soil microbes. Organic forms of N are then not available to plants for uptake and utilization until those microbes die and they are then exposed to decomposition and mineralization.

Figure 6. Mineralization – Immobilization Transformation (MIT) cycle.

The nitrogen mineralization–immobilization (MIT) cycle is a biologically mediated balance between the release of plant-available N from organic matter and the reverse reactions of sequestration in organisms and organic compounds. The continuous function of the MIT cycle is a key indicator of healthy soil, and it is central to soil fertility and plant nutrition management and efficient N fertilization.

References:
Ros, G. H., E.J.M. Temminghoff, and E. Hoffland. 2011. Nitrogen mineralization: a review and meta‐analysis of the predictive value of soil tests. European Journal of Soil Science, 62(1), 162-173.

Johnson, J.M.F., N.W. Barbour, and S.L. Weyers. 2007. Chemical composition of crop biomass impacts its decomposition. Soil Sci. Soc. Am. J. 71:155-162 doi:10.2136/sssaj2005.0419

Nevins, C.J., S.L. Strauss, and P. Inglett. 2020. Overview of key soil nitrogen cycling transformations. University of Florida IFAS Extension. SL471/SS684

Stevenson, F.J. 1982, Origin and distribution of nitrogen in soils. In: F.J. Stevenson, Ed., Nitrogen in Agricultural Soils, American Society of Agronomy, Madison, WI, pp. 1-42.

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Lettuce was seeded, then sprinkler-irrigated to germinate seed on October 14, 2024, on double rows 12 in. apart on beds with 42 in. between bed centers. All other water was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed, which contained two 25 ft rows of lettuce. Plants were thinned Nov 19, 2024, at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart. 

Sclerotia of Sclerotinia minor were produced in 0.25 pt glass flasks containing 15 to 20 sterilized 0.5 in. cubes of potato by seeding the potato tissue with mycelia of the fungus. After incubation for 4 to 6 wk at 68°F, mature sclerotia were separated from residual potato tissue by washing the contents of each flask in running tap water within a soil sieve. Sclerotia were air-dried at room temperature, then stored at 40°F until needed. Inoculum of Sclerotinia sclerotiorum was produced in 2 qt glass containers by seeding moist sterilized barley seeds with mycelia of the pathogen. After 2 months incubation at 68°F, abundant sclerotia were formed. The contents of each container were then removed, spread onto a clean surface and air-dried. The resultant mixture of sclerotia and infested barley seed was used as inoculum. Lettuce ‘Winter Select’ was seeded and then sprinkler-irrigation was initiated to germinate seed in double rows 12 inches apart on beds with 42 inches between bed centers. Plants were thinned Nov 19, 2024, at the 3-4 leaf stage to a 12-inch spacing. For plots infested with Sclerotinia minor, 0.13 oz (3.6 grams) of sclerotia were distributed evenly on the surface of each 25-ft-long plot between the rows of lettuce and incorporated into the top 1 inch of soil. For plots infested with Sclerotinia sclerotiorum, 0.5 pint of a dried mixture of sclerotia and infested barley grain was broadcast evenly over the surface of each 25-ft-long lettuce plot, again between the rows of lettuce on each bed, and incorporated into the

top 1-inch of soil. Treatment beds were separated by single nontreated beds. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of a 25 ft length of bed, which contained two 25 ft rows of lettuce. Control plots received sclerotia but were not treated with any fungicide.

For treatments first applied at seeding, sclerotia were introduced into plots before the first application of treatments. The first application for at seeding treatments was made on Jan 17, with an additional application on January 27, 2025. Some treatments had second application on Jan 30, 2024 (See table). For treatments first applied after thinning, sclerotia were introduced into plots after thinning before the first application of these treatments, with additional applications as noted in the data sheets. An initial sprinkler irrigation supplied water for seed germination, with subsequent furrow irrigations for crop growth. First sign of disease was observed on January 23, 2025. The final severity of disease was determined at plant maturity by recording the number of dead and dying plants in each plot due to Sclerotinia minor or Sclerotinia sclerotiorum (March 5, 2024). As a point of reference, the original stand of lettuce was thinned to about 65 plants per plot.

In nontreated plots, about 60% of lettuce plants were dead or dying due to infection with Sclerotinia sclerotiorum and about 50 % due to S. minor, at the end of the trial. Please refer to the data tables to compare treatments of interest, using the Least Significant Difference Value listed at the bottom of each table to determine statistically significant differences among treatments. AVIV, Luna sensation, Tesaris, Elisys, Endura fb merivon and Contans (1 application at thinning), gave the best results against Sclerotinia minor. Luna Sensation, Miravis Prime and Contans (2 applications at thinning and 14 days later) gave the best control against S. sclerotiorum (see table). table).

Phytotoxicity was not observed in any of the treatments in this trial.

Interested in ag tech? There are a couple of events you won’t want to miss. The first is the Automated Thinning & Weeding Technologies Round-Up being held TOMMOROW, Thursday, November 13th at the Yuma Agricultural Center. As the event name implies, this field day will showcase the latest technologies in automated thinning and weeding equipment operating in the field.

The motivation behind this event is that since last season, there have been several new developments in commercial automated thinning and weeding technologies. Companies that focused primarily on weeding with lasers or spot sprayers have developed new algorithms and/or improved precision so that the machines can now also be used for thinning lettuce. Significant enhancements have also been made to existing lettuce thinning machines that use AI to differentiate between lettuce plants and weeds including improved speed, durability and the ability to spot spray inter-row weeds.

For this year’s field day, we’ve added a twist we think you’ll like. The demos will be at the field scale level (> 1 acre), and most will be 20 minutes long. Approximately one half of the plot will be thinned prior to the event so that attendees can see the end result of the treatment. The other half of the plot will be used for live demonstrations on the day of the event. This format allows attendees to more fully evaluate machine performance and spend time with company representatives.

Registration begins at 7:00 am, breakfast will be served at 7:30 am and the program starts at 7:40 am (agenda below). An abbreviated version of the program will be repeated from 1:00-3:00 pm.

The second event is the two-day Desert Difference: FarmTech Connect. The first day is field day that will be held in conjunction with the Automated Thinning & Weeding Technologies Round-Up. The field days complement each other in that different types of technologies will be displayed at each event. Additionally, abbreviated versions of the 3-hour programs will be repeated from 1-3 pm so you will have the opportunity to see both. The second day is a traditional conference with keynote speakers, lightning talks and a trade show. The conference portion of the event will be held Friday, November 14th at the Yuma County Fairgrounds Legacy Event Center. Details of the Desert Difference: FarmTech Connect conference can be found here.

Fig. 1. Agenda for the Automated Thinning & Technologies field day. The event will be
held Thursday, November 13, 2025, at the Yuma Agricultural Center, 6425 W. 8th St.,
Yuma, AZ.


Fig. 2. Exhibitors and field day agendas for The Desert Difference: FarmTech Connect
and Automated Thinning & Weeding Technologies concurrent events being held
November 13, 2025, at the Yuma Agricultural Center, 6425 W. 8th St., Yuma, AZ.

What's Coming This Season
The University of Arizona Cooperative Extension in Yuma is launching an exciting new research trial that could reshape how we approach weed management and lettuce thinning in specialty agriculture. With funding from the Arizona Iceberg Lettuce Research Council (AILRC), we're evaluating the performance of robotic weeding and thinning technologies, and the results could be significant for growers across the desert Southwest.

This isn't just another field trial. This is about understanding whether precision robotics can deliver on their promise to reduce labor demands, improve crop quality, and maintain the same level of weed control that growers have come to expect from traditional hand weeding and cultivation.

The Trial Design
Our research team is comparing the performance of robotic weeding and thinning systems directly against conventional hand weeding and thinning, the industry standard that growers have relied on for decades. This head-to-head comparison will give us real data on how these technologies perform under actual field conditions in our region.

The trial is examining multiple critical factors. We're looking at weed control efficacy across different weed species, because not all weeds respond the same way to mechanical and precision spray control, and that matters. We're evaluating crop safety and plant vigor to make sure the technology doesn't compromise the crop itself. And we're assessing the practical logistics of deployment, which is just as important as the technology's performance on paper.

Why This Matters
Robotic weeding and thinning technology represents a significant shift in how we can approach labor-intensive operations. For specialty crops like lettuce and other Cole crops, hand weeding and thinning have traditionally been necessary to achieve the precision and quality standards the market demands. But labor availability, consistency, and cost are ongoing challenges for growers.

If robotic systems can deliver comparable or superior results while addressing some of these challenges, that changes the economics of production. It also opens conversations about how precision technology can reduce our reliance on certain inputs while improving outcomes.

Connected to the Desert Difference Conference
This trial is running in conjunction with The University of Arizona’s Yuma Center of Excellence for Desert Agriculture (YCEDA), Cooperative Extension, and the Yuma Agricultural Center, in partnership with Western Growers, proudly present The Desert Difference Conference. This important regional event brings together growers, researchers, industry partners, and technology innovators. The timing allows us to share preliminary insights and connect with stakeholders who are directly interested in these innovations.

The conference provides a platform for real conversations about what's working, what's not, and what growers actually need from technology. That kind of direct feedback shapes how we interpret the data and what recommendations we make going forward.

The Research Process
Over the coming weeks and months, our team will be collecting detailed data from multiple technologies. We'll be documenting weed control performance, evaluating crop responses, and assessing the practical aspects of deployment. The goal is to provide growers with evidence-based information they can use to make informed decisions about whether robotic systems make sense for their operations.

This is rigorous work. We're not just looking at whether the robots work in ideal conditions. We're stress-testing them under real-world constraints, including diverse weed species.

Stay Tuned
We'll be sharing results from this trial as the season progresses. This research has the potential to contribute meaningful insights to the conversation about precision agriculture, labor challenges, and the future of specialty crop production in our region.

If you're interested in learning more about the trial, the technologies being evaluated, or how this research might apply to your operation, reach out to Mazin Saber, mazinsaber@arizona.edu. We're here to share what we learn.

While late instar larvae of beet armyworm (BAW), diamondback moth (DBM), and cabbage looper (CL) can usually be distinguished without difficulty, identifying their eggs and early instars can be challenging, especially when these species occur together on the same hosts, such as the Brassicas. The following descriptions summarize key diagnostic features that can help to accurately identify the eggs and young larvae of these pest species in the field.

Figure 1: Diamondback moth eggs (A) and early instar larva (B).


Figure 2: Cabbage looper eggs (A) and early instar larva (B).


Figure 3: Small cluster of beet armyworm eggs (A),
newly hatched larvae (B), and 3rd instar larva (C).

To view this article as a PDF, click here and hit download.

Managing nitrogen efficiently is one of the most important and complex challenges for lettuce growers in the desert Southwest. In Yuma Valley, where over 90% of the nation’s winter lettuce is produced, irrigation and fertilization must be closely coordinated to ensure nitrogen (N) remains available in the crop root zone. Because nitrate-N is highly mobile in soil, both under- and over-application can impact crop yield, input costs, and environmental quality. Traditionally, growers and crop advisors have relied on periodic soil sampling and laboratory testing to assess nitrate levels. While accurate, these methods are time-consuming and represent only a snapshot of field conditions at the time of sampling. This limitation often makes it difficult to track rapid changes in nitrogen availability following irrigation or fertilizer events.

Introducing Near-Real-Time Nitrate Sensing Technology
Recent technological advances are helping close that information gap. Near-real-time nitrate sensors are designed to monitor soil nitrate-N directly in the field, transmitting readings continuously to an online dashboard that growers can access on their computer or smartphone. These sensors, along with soil moisture probes, offer the potential to better understand nitrogen movement and crop uptake dynamics across the growing season.

During the 2024–2025 lettuce season, the University of Arizona Yuma Agricultural Center conducted an evaluation of this emerging technology using the AquaSpy (Inc.) nitrate-N sensor system under both organic and conventional iceberg lettuce production.  

Fertilization and Sensor Setup
The conventional treatment received 200 lbs N acre⁻¹ of synthetic fertilizer applied pre-plant. The organic system received 2,000 lbs acre⁻¹ of chicken manure (4-4-2) before planting and 1,800 lbs acre⁻¹ of organic fertilizer (9-6-1) side-dressed midseason. Nitrate and soil moisture sensors were installed after crop emergence between two healthy lettuce plants, with probes positioned vertically at depths of 3, 6, 9, 12, 15, and 18 inches (Figure 1). The sensors collected hourly data on nitrate-N and soil moisture and transmitted it to a cloud-based platform for remote access. 

Figure 1. Nitrate-N sensor-soil moisture sensor from AquaSpy and soil moisture sensor
from Sentek were installed between two healthy plants in the organic lettuce production
field at the Valley Research Center at the University of Arizona, Yuma Agricultural Center,
Yuma, Arizona. 

Results and Observations
The sensors performed well under both systems, capturing seasonal changes in nitrate-N levels that corresponded with fertilizer applications and irrigation events (Figures 2 and  3). The data showed a clear rise in soil nitrate-N following the January 8, 2025, side-dress application of organic fertilizer and subsequent decreases following irrigation cycles, reflecting nitrogen redistribution in the soil profile. Comparisons with laboratory-analyzed soil samples confirmed that sensor readings followed the same general trends, with differences typically within 3–4 ppm of lab values. Although no formal statistical analysis was conducted in this initial evaluation, the consistency between methods demonstrated that near-real-time sensors can effectively capture nitrogen dynamics in the active root zone. Soil moisture levels strongly influenced sensor performance. Under persistently dry conditions, nitrate readings tended to stabilize or decline, likely due to reduced nitrate mobility and limited diffusion in the soil solution. These results reaffirm that maintaining uniform and adequate soil moisture is essential for both crop uptake and accurate sensor measurements. 

Figure 2. Soil nitrate concentrations in the first and second foot of the soil profile under
the conventional lettuce system during the 2024–2025 growing season. 

Figure 3. Soil nitrate concentrations in the first and second foot of the soil profile under
the organic lettuce system during the 2024–2025 growing season.

Ongoing Evaluation
This study represents an initial evaluation of nitrate-N sensor technology under Yuma Valley conditions. Additional research is underway to expand testing across different fields, soil types, and seasonal moisture conditions. Future work will focus on calibration, long-term accuracy, and integration with precision irrigation systems to better support adaptive nitrogen management strategies. The early results are encouraging: near-real-time nitrate-N sensing has the potential to become a valuable component of precision agriculture in the desert Southwest, helping growers maintain productivity while conserving water and nutrients.

To read the full Extension article, visit: https://extension.arizona.edu/publication/performance-evaluation-nitrate-nitrogen-sensingtechnologies-organic-and-conventional   

VegIPM Update Vol. 16, Num. 23

Nov. 12, 2025

Results of pheromone and sticky trap catches below!!

Corn earworm: CEW moth counts down in most traps over the last two weeks; about average for early November.

Beet armyworm: BAW counts increased across all locations, above average for early November.

Cabbage looper:Cabbage looper trap counts increased over the last two weeks. Overall, CL numbers this season have been higher compared to last year and above average for this time of the year.

Diamondback moth:Adult activity increased in a few locations; consistent with previous years.

Whitefly:Adult activity remains high in Welton area, for all other locations, about average for early November.

Thrips:Thrips adult activity slightly increased in a few locations; higher numbers compared to last year.

Aphids: Winged aphids continue to increase across most locations; about average for early November.

Leafminers: Adult activity continues to decrease in all areas, below average for this time of season.