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.

We conducted a session at the 2026 SW Ag Summit program on Thursday, 19 February regarding the future of the Colorado River and possible management plans for water allocations that will be very important for agriculture in the lower Colorado River Valley in the next decade. The program outline included the following speakers and components:

• Introduction – Jeff Silvertooth, Moderator, University of Arizona
• Colorado River Perspectives -
• Clint Chandler, Deputy Director, Arizona Department of Water Resources
• Vineetha Kartha, Colorado River Programs Manager – Central Arizona Project
• Tina Shields, Water Manager at Imperial Irrigation District

All current conservation and operational guidelines expire in 2026. The Department of Interior (DoI) and the Bureau of Reclamation (BoR) set 11 November 2025 as a deadline for basin states (Figure 1) to come forth with an agreement and a new plan for conservation and river management. But the basin states could not come to an agreement, so the DoI extended the deadline to 14 February 2026, and the basin states failed to reach an agreement and meet that deadline.

Figure 1. Map of the Colorado River Basin and watershed. (Source: U.S. Bureau of
Reclamation).

During the SW Ag Summit session prospects for a possible agreement among the Colorado River basin states were discussed. The Lower Basin (LB) states are unified in their efforts to find a common agreement and have offered numerous plans that include substantial conservation reductions on their part, but the Upper Basin (UB) states are unified in their direct opposition to any offers made by the LB and they refuse to make any reductions in their water allocations.

In January 2026, the Bureau of Reclamation BoR published the Draft Environmental Impact Statement (DEIS), which is required in the NEPA process. The DEIS includes five alternative approaches and analyses for consideration in the development of the new operating guidelines.

The five alternative approaches are listed below in very brief terms.

1.  No Action Alternative—Included as a requirement of NEPA, this alternative reverts Colorado River operations to the decades-old operating framework that was in place prior to the adoption of the 2007 Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead.
2.  Basic Coordination Alternative—This alternative is designed to achieve protection of critical infrastructure within the Department of the Interior and Bureau of Reclamation’s current statutory authorities if no new agreements among Basin water users are adopted.
3.  Enhanced Coordination Alternative—This alternative was developed in coordination with the U.S. National Park Service and the U.S. Fish and Wildlife Service, with input from Basin Tribes and the hydropower industry. It uses an approach of distributing storage between Lake Powell and Lake Mead that enhances the reservoirs’ ability to protect critical infrastructure and support the Colorado River Basin.
4.  Maximum Operational Flexibility Alternative—This alternative was developed by a consortium of conservation organizations with the goals of stabilizing system storage, integrating stewardship and mitigation strategies for Lake Powell and Lake Mead, maintaining opportunities for binational cooperative measures, incentivizing water conservation, and designing flexible water management strategies. It uses both system storage and recent hydrology for determining annual releases from Lake Powell and Lake Mead. Additionally, it introduces the Conservation Reserve as a flexible tool for water conservation and management.
5.  Supply Driven Alternative—This alternative proposes that Lake Powell operation be based solely on historical natural flow. It incorporates concepts from the separate proposals submitted by the Upper and Lower Basin States, as well as ideas emerging from discussions with the Basin States during spring 2025. In this alternative, annual Lake Powell releases would be determined based on a set percentage of the preceding three-year average natural flow, and Lower Basin deliveries would be determined based on Lake Mead elevation.

A lot of attention at our SW Ag Summit session was directed at a review and consideration of the five alternatives presented in the DEIS. Figure 2, which describes LB and UB reductions associated with each of the DEIS alternatives plus two others (continued current strategies and supply driven pro-rata), was presented and reviewed. It is important to note the significant reductions from each alternative on the LB allocations while the UB is not subject to any reductions. 

Figure 2. Maximum shortages for the Lower and Upper Basins for a series of
possible alternatives. (source: Arizona Reconciliation Committee).

The possible impacts from the DEIS alternatives being considered are both interesting and puzzling considering the contrasting UB and LB facts (Figure 3). Some of the basic facts associated with the economic impact of the use of the Colorado River water include:

• 75% of economic productivity from the river is associated with the lower basin.
• 75% of the 40 M people supported by the waters of the Colorado River reside in the LB as well as 74% of the jobs.
• 78% of the total crop sales derived from the irrigation with Colorado River water is from the LB.
• Agriculture in the LB is substantially more efficient, economically (based on agricultural sales) and agronomically (crop yields and productivity per unit of water utilized), than the UB.

The UB states have never utilized their complete allocation of 7.5 MAF of Colorado River water while the LB has consistently utilized their 7.5 MAF and put it to good work (Figure 3). Yet the UB states have been insistent on not making reductions on their part and insisting that all future reductions come the LB.

A huge amount of infrastructure has been developed in the LB in the past 100 years to facilitate the development and productivity described in Figure 3, all in partnership with the United States via the DoI and BoR, Good examples include: the Boulder, Glen Canyon, Parker, Davis, Palo Verde Diversion, and the Imperial Dams as well as the Colorado River Aqueduct and the Central Arizona Project. In review of the DEIS, the proposed alternatives do not seem consistent with the historical precedent established by the DoI and BoR in recognizing the value of the Colorado River in the LB.

Figure 3. Some basic Colorado River basin facts. (Source: Coalition for Protecting
Arizona’s Lifeline, Colorado River Facts.
https://protectingarizonaslifeline.com/members/)

Public input is critical to shape long-term water management for Lake Mead and Lake Powell. Comments have been openly solicited from citizens on the DoI DEIS for Post-2026 Colorado River operations via email to crbpost2026@usbr.gov The deadline was 2 March 2026. However, most of the deadlines imposed by the DoI and BoR for proposals from the basin states have passed without consequence, so perhaps they will extend the period for public comments as well.

The DEIS proposed alternatives can be accessed at the Bureau of Reclamation website. Also, a Web Tool has been developed to help explore and understand different operational strategies: Post-2026 Operations Exploration Web Tool .

Given an opportunity, it is also important to attend meetings hosted by the BoR, which are designed to provide information and collect public input.

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

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

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

This winter at the Yuma Agricultural Center, we evaluated whether Kerb (pronamide) can be effectively applied through sprinkler irrigation using a custom venturi chemigation unit, rather than a traditional ground sprayer. We also tested whether adding Hydrovant fA improves performance.

This trial was conducted under very heavy Sudan grass pressure and in cloddy seedbed conditions, making it a strong stress test of these programs.

Read the full report HERE

Key Takeaways (14 DAT – Preliminary)

1. Chemigated Kerb appears feasible and effective.
   Early results support venturi chemigation as a practical option in desert lettuce.
2. Hydrovant at 1% v/v reduced Kerb performance on Sudan grass.
   No phytotoxicity observed, but higher adjuvant rate did not improve control.
3. Seedbed quality matters.
   Cloddy conditions reduced Prefar efficacy. A fine, firm seedbed remains critical for pre-emergent success.
4. Under severe Sudan grass pressure,
   Prefar remains a suppression tool, but performance depends heavily on soil conditions.

This is a single, unreplicated screening trial. Always follow label directions and consult your PCA before adjusting programs.

Visitors are welcome to walk the plots at YAC.

Figure 1. Early results (14 DAT) show strong goosefoot control with chemigated Kerb
programs. 

This trial was made possible through partial funding from the Western IPM Center, with additional support from the University of Arizona Cooperative Extension and industry collaborators. Co-PIs on the project: Macey Keith and Wilfrid Calvin.

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. Only one Arizona population was included in this initial assessment. Additional populations from Arizona have since been collected and are currently being tested to provide a more comprehensive understanding of insecticide susceptibility across the region.

In the laboratory, larvae were exposed to insecticides at the highest labeled field rate using a leaf-dip bioassay. The insecticides evaluated included Exirel®, Coragen®, Radiant®, Baythroid® XL, Proclaim®, IncipioTM, 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 all six field populations from California and
Arizona.

Consistent Laboratory Mortality Across Regions, with Some Population-Level Variability

The levels of larval mortality caused by each evaluated insecticide were generally consistent across populations collected from major Brassica-growing regions, including Salinas Valley, CA; multiple sites in Coachella Valley, CA; and Gila Valley, AZ (Figure 2). Proclaim, Incipio, Radiant, DiPel, and XenTari resulted in high larval mortality under laboratory assay conditions for most DBM populations tested. 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 resulted in high larval mortality for the laboratory strain but 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).

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 laboratory and field populations
exposed to maximum label rates of insecticides.

Key Laboratory Findings

• Several products resulted in consistently high larval mortality under laboratory assay conditions across field-collected populations.
• Some products resulted in comparatively lower larval mortality in laboratory assays across multiple field-collected populations.
• Mortality levels varied among certain populations, suggesting heterogeneity in susceptibility.

Implications for Resistance Monitoring and Field Decision-Making

• Continued susceptibility monitoring is important for detecting shifts in population response before widespread field control issues emerge.
• Product rotation among different modes of action remains an important tactic to slow resistance development.

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

1. Calvin W., M. N. Keith, and B. McGrew. 2025. Guidelines for Effective Management of Diamondback Moth in Brassica Crops. University of Arizona Extension Publication. az2143. https://extension.arizona.edu/publication/guidelines-effective-management-diamondback-moth-brassica-crops

2. Calvin, W. and J. C. Palumbo. 2024. Chlorantraniliprole Resistance Associated with Diamondback Moth (Lepidoptera: Plutellidae) Outbreaks in Arizona Brassica Crops. Journal of Economic Entomology. toae212, https://doi.org/10.1093/jee/toae212.

Relative humidity (RH) is a microclimate variable that strongly shapes crop water relations, canopy wetness duration, and the “comfort zone” for many pests and pathogens. In leafy greens, RH influences transpiration rate, stomatal behavior, and leaf-surface wetness, which are tightly linked to crop stress and disease favorability. Using the AZMET Yuma Valley station annual summaries (1987–2025), our figures show that maximum, minimum, and average RH have declined over time, even though year-to-year variability remains evident.

In Figure 1 (maximum RH), the trendline equation is y = −0.099x + 27.1 with R² = 0.11. The negative slope indicates a gradual decline in annual maximum RH at approximately −0.099 percentage points per year (about −0.99% per decade). The yellow dotted line represents the long-term mean for the series, providing a visual reference for how many years fall above or below the multi-decadal baseline.

In Figure 2 (minimum RH), the trendline equation is y = −0.12x + 24.9 with R² = 0.33. This is the strongest RH signal among the three metrics, indicating that annual minimum RH has decreased at roughly −0.12 percentage points per year (about −1.2% per decade). The higher R² value suggests that the drying signal is more consistently expressed in the minimum RH metric, which is often closely tied to the driest parts of the diurnal cycle and evaporative demand.

In Figure 3 (average RH), the trendline is y = −0.13x + 28.2 with R² = 0.21, indicating a decline in annual average RH of about −0.13 percentage points per year (approximately −1.3% per decade). As in the other figures, the yellow dotted line marks the long-term mean, illustrating that recent years more frequently sit at or below the historical baseline.

What this means for leafy greens agronomy
A gradual decline in RH generally implies higher atmospheric demand for water (a drier air mass), which can increase crop transpiration and intensify the need for precise irrigation management. For leafy greens, this can translate into:

• Faster canopy water loss during warm, dry periods and greater sensitivity to irrigation timing.
• Potential for physiological stress when high temperature coincides with low RH, particularly during rapid canopy expansion.
• More rapid drying of leaf surfaces after irrigation events, which can influence how long a “wet canopy” persists.

What this means for IPM
Declining ambient relative humidity in the AZMET Yuma Valley record suggests the background atmosphere is gradually becoming drier, which typically corresponds to higher evaporative demand. For IPM in leafy greens, this should be interpreted cautiously: many foliar diseases are favored by extended leaf wetness and high canopy humidity, so fewer naturally humid periods may slightly reduce baseline favorability. However, in irrigated systems the conditions that matter most for infection—irrigation method and timing, canopy density, and short-term weather events—can still create localized humid microclimates and wet leaves even when ambient RH is trending downward. Likewise, lower RH combined with warm conditions can increase the likelihood of transient crop water stress if irrigation is not well aligned with demand, which can indirectly affect pest dynamics and tighten scouting and management windows. Overall, the long-term RH decline is best viewed as a shift toward greater atmospheric drying power, while day-to-day IPM risk remains primarily governed by crop stage, irrigation practices, canopy microclimate, and episodic weather rather than the trend alone.

Figure 1. Distribution and long-term trend in annual maximum relative humidity
(RHmax) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–2025; the
dashed line shows the linear trend and the yellow dotted line indicates the long-term
mean.


Figure 2. Distribution and long-term trend in annual minimum relative humidity
(RHmin) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–2025; the
dashed line shows the linear trend and the yellow dotted line indicates the long-term
mean.


Figure 3. Distribution and long-term trend in annual average relative humidity
(RHavg) at the AZMET Yuma Valley station (Yuma Valley, AZ) for 1987–2025; the
dashed line shows the linear trend and the yellow dotted line indicates the long-term
mean.

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.