At the Southwest Ag Summit (SWAG) Feb. 17-19, my project stood in full bloom as a trailer of sweet alyssum. The scent caught attention of conference attendees, and people quickly realized this was more than just a pretty trailer.

The trailer represents a project I’ve been developing, supported by the Arizona Department of Agriculture Specialty Crop Block Grant Program, to explore a bigger question for desert vegetable production:

Can off-field habitat open the door to new tactics in vegetable IPM encouraging us to think beyond traditional in-field control?

This work builds on traditional trap cropping concepts but modernizes them through mobile trap crop trailers planted with sweet Alyssum (Alyssum maritimum). Unlike fixed trap crops, the trailers can be repositioned as field conditions shift, making them adaptable to real-world vegetable production systems.

At its core, this project examines the potential to use natural insect movement as part of a broader IPM approach:

Attract → Aggregate → Eliminate.

By positioning flowering habitat outside production fields, we aim to influence insect movement and aggregation. If pests are drawn into a managed zone, that area can function as a pest sink, concentrating populations where they can be intentionally and effectively eliminated.

At SWAG, I used the trailer display to emphasize a broader principle:

IPM is a strategy.
Individual actions are tactics.

Habitat manipulation, monitoring, thresholds, and selective chemistries are not competing tactics. When layered intentionally, they reinforce one another.

In systems where insecticide options are limited, redirecting pest pressure into a managed off-field zone may strengthen the effectiveness of available control tactics. Research is ongoing to evaluate how these mobile habitat trailers influence pest pressure and beneficial insects in nearby crops.

Figure 1. Mobile sweet alyssum trailer displayed at SWAG, illustrating the use of off-field habitat as an IPM tactic.


Figure 2. Project poster displayed at SWAG illustrating key principles of IPM.

There are 20 essential nutrients necessary for complete plant growth and development. Not all are required for all plants, but all have been found to be essential to some.  Three of the 20 (carbon, hydrogen, and oxygen) and are derived from CO₂ and H₂O and are not usually considered in terms of managing a plant nutrition and soil fertility program.

The remaining 17 are commonly referred to as mineral nutrients (N, P, K, Mg, Ca, S, Fe, Mn, Mo, Cu, B, Zn, Cl, Na, Co, V, and Si).  Of the 17 mineral nutrients, N, P, and K are the macronutrients; Mg, Ca, and S are secondary nutrients; and Fe, Mn, Mo, Cu, B, Zn, Cl, Na, Co, V, and Si are referred to as micronutrients.  The terms macro-, secondary, or micronutrients do not refer to any level of importance but rather to relative amounts required by plants.

The amount of a given nutrient found in a plant will depend on several; factors, governed in general by a broad range of plant and environmental interactions.  The percentage composition of plant nutrients can vary considerably among species and locations.  Since all the mineral nutrition is provided to the plant by nutrient uptake from the soil through the root system, an understanding of the soil conditions and the effects on plant nutrition are very important. 

There is usually a rather poor relationship between the total amount of a given nutrient found in the soil (i.e., P or K) and the amount available to the plant for uptake and utilization.  This is certainly true in Arizona where our agricultural soils are commonly rather young (geologically) alluvial soils with a high native fertility level.

Soil tests are commonly used to establish a relationship between an estimated level of a “plant-available” form of a given nutrient and its sufficiency, deficiency, or toxicity for the crop in question.  The relationships between a soil test and actual crop nutrient needs are usually specific for a crop and region and a set of common soil conditions.

Developing a sound fertilization program begins with a good understanding of actual soil conditions.  The collection and analyses of a good(representative) set of soil samples and then relating that information to established guidelines are the first steps toward developing a strong soil fertility and plant nutritional management program for any crop.  This is important for the overall efficiency of a crop production system, including agronomic, economic, and environmental efficiency.

To maximize nutrient management efficiency, it is good to consider the 4R concept of plant nutrient management and application, consisting of:

 1.   Right fertilizer source at the

 2.   Right rate, at the

 3.   Right time and in the

 4.   Right place

The 4R nutrient stewardship approach utilizes the implementation of best management practices (BMPs) that optimize the efficient use of fertilizer by the crop.  The primary objective of the 4R approach and BMPs is to match nutrient supply with crop requirements and to minimize nutrient losses from fields.  Each case can vary among farms and fields, dependent on local soil and climatic conditions, crop, management conditions, and other site-specific factors.

Growers, pest control advisors, industry partners, and students are invited to attend the University of Arizona Cooperative Extension’s 2026 Downy Mildew Field Day on Thursday March 12th, 2026 at the Yuma Agricultural Center - 6425 West 8th Street, Yuma, AZ 85364.

This educational event will be centered on fungicide efficacy field trials targeting lettuce downy mildew, spinach downy mildew, and broccoli downy mildew this season. Rumor has it Jim Correll from the University of Arkansas may also be joining us at this event! His varietal trials are planted adjacent to our location, providing a timely opportunity to observe promising examples of genetic resistance to downy mildew in spinach.

Participants will have the opportunity to:

• Learn about fungicide efficacy and resistance management for local populations of downy mildew in each crop
• Hear updates on current research trials and diagnostic statistics from the 2025/2026 growing season
• Hear from industry tech reps on available chemical and biological management tools for vegetable diseases

Ask questions of the presenters and share observations from the season

The program will be conducted entirely in the field and will feature presentations, guided evaluation of the trial products, and dedicated time for discussion. Ample opportunity will be provided for feedback to ensure that future trials and research targets of the Cooperative Extension’s plant pathology program align with the current needs and priorities of Yuma County stakeholders.

The field day will begin at 9:30 am and conclude by 1:00 pm. Lunch from Tacos El Chema will be available from 12:00-1:00 pm thanks to the generous co-sponsorship from our collaborators at BASF, FMC, and Nichino!

There is no cost to attend, but registration is requested to assist with planning. Registration is quick and straightforward. To secure your spot, use the following link:

https://uarizona.co1.qualtrics.com/jfe/form/SV_exJ4HM7F1q6l2GG

2.5 continuing education credits for pest control advisors are approved for AZ and requested for CA.

See you there!

 

Event Summary:

• Date: Thursday - March 12th, 2026
• Time: 9:30 AM - 1:00 PM (programing from 9:30 am-12:00 pm)
• Location: Yuma Agricultural Center - 6425 West 8th Street, Yuma, AZ 85364
• 2.5 CEUs requested from both AZDA and CDPR
• LUNCH WILL BE PROVIDED (lunch from Tacos El Chema available from 12:00-1:00 pm)

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

We are in the process of organizing The Desert Difference: A Showcase of AgTech Opportunities for Growing in the Desert. The two-day event will be held November 13-14^th in Yuma, AZ. The first day will be a Field Day, the second will be a standard conference with keynote speakers and breakout sessions. Details of the conference will be coming soon. The focus of this article is the Field Day. As with our previous AgTech Field Days, the workshop will feature the latest ag technologies being demonstrated in the field. I’ve been reaching out to multiple companies but am sure I’m not aware of all the cutting-edge technologies out there. We would like to showcase as many innovative ag technologies as possible, so please contact me if you are interested in demoing your equipment or know someone that is. It’s an open invitation - private companies, and university and government researchers are all welcome!

Fig. 1. Previous University of Arizona AgTech Field Days.

Why is it that the summer months we spray herbicides, and they don’t work for some weed species. 

For example, during the hot time of the day and when desert weeds are stressed for moisture even the highest rate of Glyphosate sometimes is not effective.
Some desert weeds develop physical characteristics and growth habits that equip them to survive hot and dry conditions. We have seen that some species have different response to herbicides in cool areas than our low desert. 

Weeds in the desert have a thicker skin to preserve water. The stomates, which are the pores found in the epidermis of leaves, stems, and other organs, controlling the rate of gas exchange between the internal air spaces of the leaf and the atmosphere are closed¹. Plant transpiration is reduced, and this interferes with the translocation of herbicides in the weeds.

Take as an example Purslane, which has very succulent leaves and stems and can survive incredibly high hot and dry conditions. Then when weather is more favorable it comes out of survival mode to start growth again at the presence of moisture.

Other perennial species have underground structures that help them survive such as Nutsedge and bermudagrass have tubers, and rhizomes.
Lundkvist² stated:” The conclusion is that environmental conditions that promote growth rate of the weed stand will also increase the herbicide effect. The results were based on data from two field experimental series performed at six sites in southern Sweden during 1991–1994”.



 References:
1. https://simple.wikipedia.org/wiki/Stomata
2. A. Lundkvist,
Predicting optimal application time for herbicides from estimated growth rate of weeds,
Agricultural Systems,
Volume 54, Issue 2, 1997,

I am delighted to embark on my first produce season here in Yuma, AZ. I am looking forward to becoming acquainted with the growing region this fall as we begin identifying tools that can enhance our pest management strategies, specifically focusing on organic solutions for managing insect pests in the Desert Southwest. It is also important for me to gain a deeper understanding of the challenges and issues you are facing in the field. We are eager to evaluate both current and new biopesticides in our upcoming trials and look forward to engaging with potential collaborators. 

Here is a list of our fall 2024 trials: 

1- Evaluation of selected bioinsecticides against Lepidopteran pests in Brassicas 

2- Evaluation of selected bioinsecticides against whiteflies in Brassicas 

3- Alternative bioinsecticides for thrips management in lettuce 

4- Assessing the effectiveness of beneficial insects (T. brassicae, T. pretiosum, and green lacewings) release for diamondback moth control in Brassicas 

I hope everyone’s season gets off to a fantastic start. Please contact me or Macey if you have specific pest issues, biopesticides, or other organic IPM practices you would like us to evaluate. Your expertise is truly invaluable to us! 

Contact Information: 

• Wilfrid Calvin
Assistant Professor & Extension Specialist
Cell: (979) 709-9762
Office: (928) 782-5861
e-mail: wilfridcalvin@arizona.edu 
 

• Macey Keith
Assistant in Extension
Cell: (928) 580-5785
e-mail: maceyw@catmail.arizona.edu 

Organic lettuce is a high-demand crop for organic nitrogen sources. Lettuce requires a substantial amount of nitrogen to support its growth, particularly during the heading stage when most nitrogen uptake occurs. This demand is driven by its rapid growth rate and the production of large leaf biomass. The organic iceberg lettuce production system is gaining importance both locally and nationally due to the growing demand for healthy, hygienic, and safe food, along with the need for long-term sustainability (McGrady et al, 1991; Koide & Bache, 2021).

In arid regions like Yuma, AZ, where annual precipitation is often less than 3 inches, long periods of drought and frequent heat waves create challenging conditions for soil health. Limited rainfall restricts natural moisture replenishment, leading to soil dehydration and reduced microbial activity. Prolonged drought intensifies soil compaction and salinity buildup, while extreme heat accelerates organic matter decomposition, further depleting essential nutrients. These factors collectively hinder soil fertility, making it more difficult to sustain productive organic lettuce farming without strategic soil health management practices.

Therefore, many questions arise about whether combining fertilizers with biostimulants may improve soil health, particularly soil water retention while also enhancing crop growth, development, and yield. Several studies indicate that the combination of biostimulants with organic fertilizers has a positive effect on soil structure and mitigates stress and crop yield (Rodgers et al., 2020 Li et al., 2021; Zhang et al., 2021). They enhance soil physical properties and boost crop productivity in multiple ways. The potential of biostimulant to align with sustainability policies offers promising prospects for the future of agriculture. Given the environmental challenges associated with current fertilization practices, there is a pressing need to prioritize research that optimizes plant-microbe interactions to establish more sustainable agricultural systems. Biostimulants can positively influence a plant’s response to stress and adverse environmental conditions, promoting growth by enhancing germination, root development, and the plant's ability to access water and minerals.

Thus, investigating the magnitude of the potential impacts of coupled organic fertilizer and biostimulant on soil properties (i.e., soil water retention), lettuce crop growth development and yield for local or regional conditions can result in more effective, relevant, and practical information that can aid users in making management decisions. To address the identified knowledge gaps, preliminary field experiments were conducted during the Fall 2024 growing season at the Valley Research Center, University of Arizona Yuma Agricultural Center. These experiments aimed to establish foundational data to support this proposal.

The field (Figure 1) was planted on October 29th, 2024, and the pre-sprinkler irrigation strategy was utilized to ensure germination which was noticed on November 06, 2024. On December 5, when the lettuce was about 1 inch tall, the first application of 2 quarts/acre biostimulant (FBS Organics® Zicron®) was applied via the subsurface irrigation system. A second application of 1 gallon/acre was applied on January 9, 2025.

To quantify changes in soil water retention, three types of high-tech sensors (Figure 2) were installed after crop emergence to continuously monitor soil moisture levels, along with other key parameters. Additionally, plant height (Figure 3) measurements have been taken to assess the impact of biostimulants combined with organic fertilizers on crop growth and development. Finally, yield differences will be evaluated after harvest to determine the overall effectiveness of these treatments (Figure 4). Stay tuned for the results and conclusions after harvesting.

Figure 1. Satellite image view of the organic research field in the Valley Research
Center at the University of Arizona, Yuma Agricultural Center, Yuma, Arizona.


Figure 2. Nitrate-N sensor and soil moisture sensor from AquaSpy and soil
moisture and salinity sensors 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.

Figure 3. Plant height measurements in the field at the Valley Research Center at
the University of Arizona, Yuma Agricultural Center, Yuma, Arizona


Figure 4. Lettuce few weeks before harvesting in the field at the Valley Research
Center at the University of Arizona, Yuma Agricultural Center, Yuma, Arizona.

 

VegIPM Update Vol. 17, Num. 5

March 4, 2026

Results of pheromone and sticky trap catches below!!

 

Corn earworm:  CEW moth activity seen in some areas, but numbers have been low; About average for this time of season.

Beet armyworm: BAW numbers decreased across most locations since last collection. Above average  for this time of the season. Historically BAW numbers peak in March/April.

Cabbage looper:  Cabbage  looper moth activity decreased across most sites since last collection, but  remains higher than average for late-February. Historically cabbage looper moth  numbers peak in March/April. 

Diamondback moth: Adult activity remains steady across most locations. About average for this time of the year. 

Whitefly: Adult activity remains low across all locations, about average for this time of year.  

Thrips:  Thrips adult activity remains steady across locations, about average for this time of year. Expect numbers to continue increasing as temperatures warm up.

Aphids:  Winged aphid numbers decreased at most sites since last collection; below average for this time of the year.

Leafminers: Adult leafminer activity remains steady, high numbers seen in Yuma Valley, about average for this time of the season.