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.

On March 30th, I shared a newsletter highlighting an increase in celery samples exhibiting symptoms consistent with black heart and black streak abiotic disorders, associated in timing with the mid-March heat wave. At that time, affected plants showed elongated necrotic pitting accompanied by pronounced horizontal cracking along the inner petioles. In more severe cases, there was complete breakdown of young tissues within the heart, including petioles and emerging leaves. Importantly, diagnostic testing on those early samples returned negative results for the common viral pathogens typically considered in the differential diagnoses fitting these symptoms. 

Early black heart symptoms 


Late black heart symptoms + secondary colonization 

Black streak of celery

The YPHC has since received a new sample that changes part of that picture. This most recent submission tested positive for celery mosaic virus (CeMV). In addition to sunken discolored stalk lesions that could potentially be mistaken for early black heart or black streak, the plants in this sample exhibited severe foliar symptoms. Leaf symptoms included deformation including curling and marginal distortion. The leaves also showed distinct mosaic patterning, yellowing, and streaking, all of which are typical characteristics for viral infections. 

Sunken, discolored lesions on celery petioles 


Broad yellowing and mosaic pattern (left) and severe leaf distortion
and mild mosaic (right) on the foliage 

Mosaic, yellowing, and leaf distortion combined on the same petiole

Additional symptoms associated with CeMV can include overall plant stunting and abnormal growth habit (Greer et al. 2024). In some cases, outer petioles may distort severely and begin growing horizontally, giving the plant a flattened appearance. Symptom severity can vary depending on the strain of the virus and environmental conditions during host infection. Be on the lookout for these additional foliar symptoms if you’re seeing sunken petiole lesions as a possible indicator of viral infection. Early infections, symptoms on different varieties of celery, or symptoms caused by different viral strains of CeMV may not look identical in severity or expression as the sample photographed here. CeMV is transmitted by aphids in a non-persistent manner and may also be spread mechanically through wounds introduced during field activities (Karanfil & Randa-Zelyüt 2025). It has not been reported to be seedborne. Fungicides are not effective against plant viruses, and while insecticides may reduce aphid populations, they are generally not effective at preventing virus transmission due to the rapid transmission following the initiation of aphid feeding that occurs before the insecticide has a chance to act on the vector (Greer et al. 2024). We will continue monitoring all incoming celery samples to determine whether this represents an isolated case or a broader trend developing alongside the ongoing celery abiotic disorders.

Sources and further reading:
Greer, C., Koike, S., & Turini, T. “Celery Mosaic Virus.”  Agriculture: Celery Pest Management Guidelines. University of California Agriculture and Natural resources, 2024. URL: https://ipm.ucanr.edu/agriculture/celery/celery-mosaic-virus/#gsc.tab=0 (Accessible 4/28/2026)

Karanfil, A., & Randa-Zelyüt, F. “Celery Mosaic Virus.” Compendium of Phytopathogenic Microbes in Agro-Ecology. Springer Nature, 2025. 153–160.

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 

 

This week, we initiated a trial investigating the effectiveness of applying fungicides post-emergence with an alternative tool, a point injection applicator, to control the pathogen which causes Fusarium wilt of lettuce. The hypothesis is to inject fungicide where it is needed to protect plants from the soilborne disease – in the root zone, without injuring crop roots. We are doing this with a point injection applicator, a device designed to apply ag chemicals post emergence with minimal root damage and soil disturbance. The applicator utilizes hollow pointed tips attached to a rotatable wheel to inject liquid products into the root zone at precise intervals and depths (Fig. 1). The advantage of point injection compared to conventional shank injection is that root pruning is minimized, reducing the number of wounds that provide a pathway for the pathogen to infect the plant. Stay tuned for trial details and results. 

Fig. 1. Point injection applicator operating in iceberg lettuce. 

Fig. 2. Click here or the image above to see the point injection system in action.

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.

Organic vegetable production in the desert Southwest requires a different mindset for insect management. Our insecticide options are more limited, and results can be more variable, so success depends on using these tools thoughtfully within an IPM framework. In my Southwest Ag Summit talk, I focus on how organic materials perform under desert conditions.


Session details below:
AFTERNOON BREAKOUT SESSION
Thursday, February 19, 2026 | 1:30 PM – 3:30 PM

Vegetable IPM

Dr. Palumbo Veg IPM Insecticide Program: 2025–2026 Efficacy trials — Dr. Samuel Discua Duarte, Yuma Ag Center
Insecticide Options for Insect Pest Management in Organic Vegetable Production — Dr. Wilfrid Calvin, UofA
Area Wide Trapping Network: Program Update and Expansion — Macey Keith, UofA
Advances in Vegetable Weed Management: Herbicides and Chemigation Strategies — Dr. Mazin Saber, UofA

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. 9
April 29, 2026

Results of pheromone and sticky trap catches below!!

Corn earworm:  CEW numbers remained steady at most locations over the last two weeks. CEW is active throughout the summer and high numbers are expected leading into the next produce season.

Beet armyworm:  BAW activity remained steady over the last two weeks. Historically adult BAW is collected through the summer, although numbers are lower compared to Mar-Apr seasonal highs.

Cabbage looper:  Cabbage looper moth activity remained steady over the last two weeks. Numbers are expected to decrease as temperature gets warmer.   

Diamondback moth: Adult DBM numbers continued to decrease across most locations. Based on other years data, DBM numbers are expected to continue decreasing as cole crops acres decrease.  

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

Thrips: Adult thrips activity remains steady across locations. Historically, western flower thrips numbers peak in May.  

Aphids: Winged aphid numbers continued to decrease at most sites in the last two weeks. Winged aphids disappear from our traps after April as temperatures become too hot for aphids.  

Leafminers: Adult leafminer activity decreased over the last collection. Leafminers are collected in our traps throughout the summer.