The fall produce season is off to the races, and so is our diamondback moth (DBM) monitoring project. Although our area-wide trap network is still capturing zero adult DBM moths, AZDA inspectors are already detecting DBM larvae in incoming brassica transplants.

During the first month of inspections in August, AZDA reported 66 shipments of brassica transplants from six California counties. DBM was detected in 28 of those shipments—more than 40%.

These shipments enter Arizona under new phytosanitary requirements intended to reduce the movement of DBM, including inspection and certification within 24 hours of shipment. Understanding what an AZDA detection at arrival means for subsequent DBM risk in the field is therefore an important part of evaluating how well this prevention system is working.

Does a detection at arrival translate into DBM establishment and greater pest pressure after planting—or do some detections pose little subsequent risk?

With funding from the Yuma Center of Excellence for Desert Agriculture (YCEDA) Small Grants Program, we are following inspected transplant lots after planting and linking AZDA inspection findings with subsequent DBM observations and management in commercial fields.

Our goal is to determine which observations made during transplant inspections are useful indicators of subsequent field risk and use that information to develop a practical, risk-based inspection framework for AZDA, growers, and PCAs. Ultimately, better understanding the connection between detections at arrival and what happens in the field can help focus scouting and management where they are most needed—and provide evidence for improving transplant inspection and prevention efforts.

 

Additional Resources

AZDA Director’s Administrative Order 26-03: Exterior Quarantine for Diamondback Moth

AZDA DAO 26-03 Industry Guidelines for Diamondback Moth

In the last two editions of this UA Vegetable IPM Newsletter, I have presented a melon (Cucumis melo ‘reticulatus’ L.) crop phenology model (Figure 1; Silvertooth, 2026) based on heat unit accumulations (86/55 ºF thresholds). This model can be used for predicting and tracking crop development and identifying important stages of crop growth and development (crop phenology).  

I have utilized data from AZMET for three locations in the Yuma area as examples for this season. The HU accumulations from 1 January 2026 for a set of four possible 2026 planting dates are listed in Table 1. The HU accumulations from 1 January 2026 to 10 May 2026 for these sites are listed in Table 2.

The HU accumulations after planting (HUAP) for these four possible planting dates for three Yuma area locations to 10 May 2026 are shown in Table 3. The HUAP values in Table 3 are simply the difference between the values in Tables 1 and 2.  

An example for the Yuma Valley 15 January 2026 planting date is: 1793 - 95 HU = 1698 HUAP for this case.

The information in Table 3 can help serve as a reference to check for melon crop development in the field against this phenological model in Figure 1. With this information we check actual field condition, evaluate crop status, and make some projections on crop development and management.  

An important point of reference with the use of this or any similar model is the degree of variability in the normal plant growth and development patterns. Based on a 95% confidence interval, the standard deviations for each benchmark stage of growth associated with the model in Figure 1 are listed in Table 4. Commonly, we use a general rule of thumb in using this model in the field considering natural variation of approximately 100-150 HU, broadening from early in the season to later stages of development. That can commonly equate to 7-10 days later in the season.

Crop development can be delayed or accelerated based on several factors, some of which are listed in Table 5. A constructive aspect of using a model like this is considering the driving forces in crop development and how they interact.

Reference:
Silvertooth, J.C. 2026. 2026 Melon (Cantaloupe) Crop Growth and Development. University of Arizona Vegetable IPM Newsletter, Volume 17, No.9, 24 April 2026.

Table 2. Heat unit accumulations (86/55 ºF thresholds) after 1 January 2026 to 26 April
2026 utilizing Arizona Meteorological Network (AZMET) data for each representative
site.

H_{T = Heat Unit Total Accumulation.}

Table 2. Heat unit accumulations (86/55 ºF thresholds) after 1 January 2026 to 26 April
2026 utilizing Arizona Meteorological Network (AZMET) data for each representative
site.

H_{T = Heat Unit Total Accumulation.}

Table 3. Heat unit accumulations (86/55 ºF thresholds) after planting (HUAP) from four
possible 2025 planting dates and three sites in the Yuma area on 26 April 2026 utilizing
Arizona Meteorological Network (AZMET) data for each representative site. Each value
is rounded to the next whole number. Note: the values in Table 3 are determined by
taking the difference between the HUs for each representative site and four planting
dates in Tables 1 and 2.


Table 4. Standard deviations for the phenological model in Figure 1 based on heat unit
accumulations (86/55 ºF thresholds) after planting (HUAP) based on 95% confidence
intervals.


Table 5. Factors that can delay or stimulate crop phenology. 


Figure 1. Melon (cantaloupe) phenological development model expressed in Heat Units
Accumulated After Planting (HUAP, 86/55 ^oF).

It’s been anything but a smooth Spring melon season this year. Mild winter temperatures have contributed to the persistence of weeds and whitefly populations culminating in high viral pressure observed from the very first melon plantings onward. Through a collaborative effort between the University of California, USDA, and University of Arizona we would like to invite growers, PCAs, farm managers, researchers, and other stakeholders from the desert melon production regions in California, Arizona, and Mexicali to join us for a stakeholder meeting to discuss field observations and disease management research priorities.  

This meeting will provide an opportunity to review this season’s observations and trends across production areas, hear research and strategy updates from plant pathology specialists, and, most importantly, create space for discussion among stakeholders to better understand what is happening and give input on the disease management research priorities you want to see pursued moving forward. Topics and invited speakers include:

• Bill Wintermantel (USDA-ARS) – Overview of cucurbit viruses affecting desert melon production
• Arun Babu (UCCE Imperial)– Whitefly populations and insecticide efficacy trials in Imperial Valley
• Samuel Discua (University of Arizona, Yuma) – Whitefly populations and insecticide efficacy trials in Yuma, Arizona
• Chris Detranaltes (University of Arizona, Yuma)– Viruses and other pathogens recovered from symptomatic melon plants in Yuma, Arizona
• Ana M. Pastrana (UCCE Imperial) – Viruses and other pathogens recovered from symptomatic melon plants in Imperial Valley, California

 

Meeting details:
Where: AgWest Imperial 485 Business Pkwy, Imperial, CA 92251
When: June 2, 2026 10:30 am – 12:30 pm (lunch to follow until 1:00 pm)

Lunch will be provided. Please register here if you plan to attend so we can have an accurate food count and seating estimate: Registration Survey

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 

For those interested in in-row weed control, checkout the quality video below (Fig. 1) on how finger weeders (Fig. 2) are being used on a 3,600 acre organic cotton farm in Texas. The grower states that finger weeders help him achieve 95-97% weed control and are a highly cost-effective tool for lowering hand weeding costs. 

Fig. 1. Carl Pepper discusses how finger weeders are used to control in-row weeds on
his 3,600 acre organic cotton farm. Click here or on image to view. (Photo credit: Tilmor
LLC, Dalton, OH)


Fig. 2. Finger weeders, an in-row weeding tool, operating in seedling cotton. Finger
weeder pairs are centered on the seed row and overlapped slightly to loosen soil in the
row and uproot small weeds.

As we wrapped up our chemigation trial, I would like to extend our sincere thanks to all the participating partners and to every grower, PCA, and representative who took time from a busy schedule to visit and observe the trial.

With spring well underway across the Yuma valley, weed proliferation is accelerating rapidly. Both in winter vegetable crops approaching harvest and in newly planted, emerging warm-season crops. Proactive and effective weed management remains essential for crop protection, harvest efficiency, and long-term field productivity within this desert production system.

The Yuma Integrated Weed Management Program supports growers and pest control advisors by providing locally relevant, research-based guidance to address current and emerging weed challenges.

Crops We Typically Support
Our program works closely with the Yuma production system to address weed management challenges in:

• Leafy Greens: Lettuce, spinach, and other leafy greens
• Cole Crops: Broccoli, cauliflower, and cabbage
• Spring and Warm-Season Crops: Watermelon and cantaloupe

 

Common Weed Challenges This Time of Year

During April in Yuma Valley, we typically observe:

• Heavy emergence of summer annual weeds as temperatures rise
• Residual winter weeds impacting harvest operations and field cleanliness
• Questions about herbicide efficacy relative to irrigation timing and soil moisture
• Crop safety concerns as production cycles overlap between winter and warm-season crops
• Early signs of herbicide resistance or shifts in weed populations

Timely management decisions made now can significantly reduce weed pressure throughout the season and help prevent seed accumulation for future crops.

How the Yuma Weed Management Program Help
We provide direct, practical support to growers and pest control advisors, including:

• Precise identification of weeds at both early and advanced growth stages
• Evaluation and optimization of pre- and post-emergence herbicide programs
• Guidance on weed resistance management and herbicide rotational strategies
• Integration of chemical, cultural, and mechanical control options
• Label interpretation, application timing, and crop safety considerations
• Applied on-farm research trials conducted under Yuma-area conditions

Our focus is on solving the real-world, field-level weed problems that are unique to the Yuma region.

Get in Touch — We Are Here to Help

If you are experiencing weed problems in your fields, have concerns regarding herbicide efficacy or crop response, or need assistance planning current or future weed management programs, we encourage you to reach out.

Growers — Contact us for weed identification, control options, and management strategies tailored to the current season and your specific crops.

PCAs — We welcome collaboration and field observations. Working together allows us to address weed challenges more effectively across the entire Yuma production system.

Early communication leads to better outcomes. The Yuma Weed Management Program, operating within the broader Integrated Pest Management framework, is available throughout the season to help you manage weeds effectively and sustainably.

Background
The University of Arizona Specialty Crops IPM program supports the agricultural community by delivering research-based solutions for insect pest management, with a strong emphasis on desert production systems in Yuma and surrounding regions. The program addresses key challenges, including insecticide efficacy, resistance management, biological control, and the development of practical, economically viable IPM strategies through applied research and targeted Extension and outreach efforts. The program integrates research and Extension to improve insect pest management by developing and facilitating the adoption of farm-ready tools and promoting sustainable production systems that reduce reliance on chemical inputs.  

I need your help!  
I am conducting this survey to gather honest, anonymous feedback on my program focus, activities, and accomplishments so far. Your input will help me to improve the program and serve you more effectively. All responses are anonymous and will remain confidential. I greatly appreciate your honest responses to help me improve my work. Please click on the link below to take the survey.

Survey link: https://uarizona.co1.qualtrics.com/jfe/form/SWCV_5nz4KTx9reNsavY

Thank you for your time and support! 

Water conservation is becoming increasingly important for desert growers as reduced snowpack, drought, and climate variability continue to pressure irrigation water supplies. To evaluate whether PolySorb could support irrigation water savings under desert conditions, we conducted a large-field evaluation using reduced irrigation levels with and without PolySorb.

The field study included three irrigation levels: 100% full irrigation treatment (FIT), 75% FIT, and 50% FIT. The 100% FIT treatment was used as the full-irrigation standard. PolySorb was evaluated under the reduced irrigation treatments, 75% FIT and 50% FIT, and was applied at a very low rate, approximately 2 inches below the soil surface (Fig. 1). 

Figure 1. Field application of PolySorb in a desert crop production system at Yuma
Valley Farm Research Center at the University of Arizona.

The full irrigation treatment, 100% FIT without PolySorb, produced 17.5 tons/ac. When irrigation was reduced to 75% FIT without PolySorb, yield declined to 14.7 tons/ac. A stronger yield reduction occurred at 50% FIT without PolySorb, where the yield was 7.8 tons/ac. Adding PolySorb improved yield under reduced irrigation. The 75% FIT + PolySorb treatment produced 16.8 tons/ac, which was very close to the 17.5 tons/ac observed under 100% FIT without PolySorb. This represents only a 0.7 tons/ac difference, or about 4% lower yield, while using 25% less irrigation water. At the 50% irrigation level, 50% FIT + PolySorb produced 12.0 tons/ac, compared with 7.8 tons/ac with 50% FIT alone. This was an increase of 4.2 tons/ac, or about 54% higher yield than the same irrigation level without PolySorb (Fig. 2) 

Figure 2. Fresh yield response to irrigation level and PolySorb application. Yield was
17.5 tons/ac under 100% FIT without PolySorb, 14.7 tons/ac under 75% FIT without
PolySorb, and 7.8 tons/ac under 50% FIT without PolySorb. Adding PolySorb increased
yield under reduced irrigation, producing 16.8 tons/ac at 75% FIT + PolySorb and 12.0
tons/ac at 50% FIT + PolySorb.

These results suggest that PolySorb may help improve irrigation efficiency under desert production conditions, especially at moderate deficit irrigation. The strongest response was observed at 75% FIT + PolySorb, where yield was comparable to full irrigation. PolySorb also improved yield at 50% FIT, although yield remained lower than the 75% FIT without PolySorb treatment.

From a practical grower perspective, PolySorb should not be viewed as a stand-alone solution to water scarcity. However, it may be a useful component of an integrated water-management strategy that includes irrigation scheduling, soil moisture monitoring, crop evapotranspiration information, and efficient irrigation delivery systems. More field testing across crops, soil types, irrigation systems, and seasons is needed, but these results indicate that PolySorb could be a promising approach to help conserve irrigation water in desert agriculture. 

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.