The Yuma agriculture community lost a legend with the passing of our friend and colleague, Vicki-Lynne Scott. Vicki was a friend to everyone she met and a mentor to countless people across our agricultural community, leaving a lasting impact on Yuma agriculture and University of Arizona Extension.

I was especially fortunate to work closely with Vicki these past few months as she brought me into conversations surrounding the diamondback moth challenges facing our vegetable systems. She believed in me as an entomologist and had confidence in my abilities before I fully recognized them myself. She cared deeply about helping growers and making sure the right people were at the table to move our industry forward. Vicki also loved the Veg IPM Newsletter and often referenced Dr. Jeff Silvertooth’s work and the value of University of Arizona Extension programs.

As our community moves forward, it is difficult to imagine facing these agricultural challenges without Vicki’s guidance. Her legacy will live on in the countless people she mentored and supported throughout her life.

Vicki never left any of us wondering how deeply she cared about the people and community around her. Thank you, Vicki, for believing in people, bringing us together, and leaving our agricultural community better than you found it.

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).

In the last edition of the Veggie IPM newsletter I advertised a collaborative incident response meeting to this year’s unprecedented spring melon virus epidemic. This meeting was made possible through a collaborative effort between the University of California’s Cooperative Extension, USDA-ARS, and the University of Arizona’s Cooperative extension, and of course through the participation of the melon growing community of the Desert Southwest. The goal of the meeting was to revisit currently available management methods and practices, discuss this year’s potential epidemiological trends and pattern observations, and, very importantly, to get a sense of the economic impact this epidemic was having as a result of this anything-but-normal season.

The community’s response to this call to action and reactionary meeting, a career first for me, was overwhelmingly encouraging in many ways. Despite limited advertising, we had excellent turnout and participation, with over 70 attendees including growers, PCAs, industry representatives, and academics filling the room and contributing valuable insights to the open forum discussion. A post-meeting survey of attendees managed to capture representation from a total of 6,825 acres of spring melon grown across Arizona, California, and Mexicali.

I thought some of the key economic, epidemiological, and entomological highlights from the community survey worth sharing were the following:

• Whitefly infestations were reported on 6313 out of 6825 surveyed acres.
• Of those infested acres about 40% of the crops were reported to have whitefly-vectored virus symptoms by the time of the meeting.
• The overall estimated yield loss attributed to whitefly and virus pressure averaged 20% and ranged from 0% in early-planted melons to 100% in late-planted melons within individual plantings.
• 100% of surveyed acres received whitefly control applications consistent with the melon IPM recommendations developed and endorsed by Dr. Palumbo.

I cannot express my gratitude enough to everyone who participated in the meeting, who added to the “debrief” discussion, and took the time to complete the economic loss survey. We never know who will be reviewing and making crucial decisions on our requests for funding or support for our applied research and for developing new IPM strategies to address these challenges. In many cases, those decision-makers are far removed from what we are experiencing here on the ground. Maybe they work in specialty crops but in a climate as different as New Jersey or they may be an expert in whitefly-vectored viruses but work only in field crops of North Dakota. When these often-anonymous gatekeepers critical to advancing our requests for support hear that the whitefly-vectored melon virus epidemic of the Desert Southwest was record-setting in 2026, we cannot afford to simply hope that they’ll grasp what that meant the way we can. We lived the reality of it, but it’s just a sentence on a piece of paper to them. The information you provided is invaluable in helping us tell that story in a way others, no matter how separated from our community they are, can understand. Your efforts and shared experience put real numbers and quantifies the impact these plant health challenges have on our industry.

And these numbers are what are critical for strengthening and justifying grant proposals and requests for federal dollars to research the next best management strategy, for informing regulatory and pesticide review processes who may or may not see the value in the inputs that make our industry thrive, and, perhaps most important to me and my colleagues, for advancing our understanding of regional and seasonal pest trends under unusual and atypical conditions so that we can build in more flexibility to our recommendations and strategies. Your participation helps ensure that the true scale and significance of our plant health challenges are recognized, documented, and acted upon.

From the bottom of my heart, thank you.  
-Chris

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

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.

Weed control in wheat and barley in the Southwestern United States faces significant challenges, including high winter temperatures, extensive irrigation, and limited crop rotation options. Although wheat and barley are naturally competitive crops, research indicates that weeds can reduce yields, hinder harvesting, increase grain impurities, cause grain discoloration, and lead to insect or mold problems during storage if not managed effectively.

An Integrated Pest Management (IPM) approach—which combines prevention, cultural practices, and the appropriate use of herbicides—offers the most sustainable and reliable weed control within wheat production systems in low-desert regions.

Focus on Early Control
Weeds that emerge simultaneously with the wheat crop, or shortly thereafter, cause the greatest yield losses. Weed species typically include annual ryegrass, wild oats, Italian ryegrass, Canarygrass species, London rocket, various mustard species, and Fiddleneck. Fields should be free of weeds at the time of planting and must be kept clean until the onset of the tillering stage.

Cultural Practices Remain Essential

• Utilize vigorous, well-adapted wheat varieties that exhibit strong early-season growth.
• Plant at recommended seeding rates—or slightly higher—in fields known to be heavily infested with weeds. Encourage rapid canopy closure through uniform growth and narrow row spacing.
• Avoid excessive nitrogen application during early growth stages, as this may favor weed growth over the wheat crop.

Recommended Herbicide Programs (Examples of Options)

Note: Always follow the instructions on the product label specifically for your state, wheat variety, soil type, and growth stage. The rates listed below reflect ranges commonly used in the Southwestern United States.

1. Pre-plant or Pre-emergence (Primary Residual Herbicide). Aims to control early weed growth and reduce reliance on post-emergence herbicides.
1. Pendimethalin (Prowl® H₂O, Group 3) 1.0–2.0 pints/acre
1. Applied pre-emergence or pre-plant incorporated; requires irrigation or rainfall for activation. Provides residual control of annual grasses and certain small-seeded broadleaf weeds.

OR

1. Trifluralin (Treflan® HFP, Group 3) 0.75–1.5 pints/acre, pre-plant incorporated. Common in conventional tillage systems.
1. Early Post-Emergence Stage (Grasses with 2–4 leaves; Wheat Tillering Stage)
1. Axial® XL (Pinoxaden, Group 1) 8.2–16.4 fl oz/acre
1. Provides effective control of wild oats and annual ryegrass. Apply when grasses are small; use higher rates under heavy pressure or if resistance is suspected.
2. 2,4-D Amine (Phenoxy Herbicide - Group 4) Mode of Action: Synthetic auxin (growth regulator) 0.5–1.0 pint/acre
1. Controls mustards, London rocket, and other winter annual broadleaf weeds. Apply after tillering and before jointing to avoid crop injury.  

OR

1. MCPA Amine (Group 4) Mode of Action: Synthetic auxin (growth regulator) 0.5–1.0 pint/acre
1. MCPA is often preferred over 2,4-D in areas with nearby cotton or broadleaf specialty crops due to its lower volatility, though care is still essential. Often tank-mixed with bromoxynil, clopyralid, or fluroxypyr for a broader weed spectrum.
1. Fields Dominated by Broadleaf Weeds
1. Bromoxynil + MCPA (Group 6 + 4) 1.0–1.5 pints/acre
1. Best utilized on small, actively growing broadleaf weeds under warm conditions. Less effective on older, established weeds.  

OR

1. Harmony Extra (ALS Inhibitor, Group 2) 0.45–0.9 oz/acre
1. Effective against many winter annual broadleaf weeds; however, rotation is recommended to minimize the risk of weed resistance.

Resistance and Integrated Pest Management (IPM) Considerations  

Rotate the use of multiple effective herbicides.  

• Avoid repeated annual use of Group 1 or Group 2 herbicides alone.
• Apply herbicides to small weeds; delayed application reduces their efficacy.
• Control late-emerging weeds to limit seed accumulation.
• Integrate herbicides with competitive crop varieties, appropriate fertilization, and uniform crop growth.

Recommended Reading
Growers and PCAs are strongly encouraged to review the following foundational reference guide for additional details regarding weed biology, application timing, and appropriate herbicide options for Arizona’s low deserts:

• Ottman, M., & Tickes, B.  Weed Control for Wheat and Barley in the Low Deserts of Arizona. University of Arizona Cooperative Extension, AZ1268 (Revised).
• This publication provides detailed guidance on cultural practices, herbicide timing by crop and weed growth stage, and comparative herbicide performance for both grasses and broadleaf weeds.

Bottom Line
Successful weed management in wheat and barley crops across the Southwestern United States relies on early-season management, high crop competitiveness, and the timely and appropriate application of herbicides. Integrating extension-based cultural practices with weed management programs that are mindful of herbicide resistance remains the most effective strategy for safeguarding both crop yield and grain quality.

Extension Support and Collaboration
I am more than happy to conduct field visits, assist with weed identification and management decisions, or collaborate on herbicide efficacy trials targeting weed problems in wheat and barley. Please feel free to reach out to discuss on-farm visits or research opportunities. 

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

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. 

Dec. 10, 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 December.

Beet armyworm: BAW counts decreased across all locations over the last two weeks; but activity remains in most areas. Above average for December.

Cabbage looper: Cabbage looper trap counts decreased across locations except for East Gila. Activity remains at all locations and above average for early December.

Diamondback moth: Adult activity continues to increase across most locations. About average for early December. Historically DBM adult numbers peak around Dec-Jan and remain high until the end of the produce season.

Whitefly: Adult activity decreased across all locations, about average for early December. Expect numbers to remain low as temperatures continue to fall. Historically, whitefly numbers typically peak in October and then again in July-Aug.

Thrips: Thrips adult activity continues to decrease across locations, about average for this time of year. Historically, thrips numbers start picking up again until mid to late January.

Aphids: Winged aphid counts were low across all sites; below average for early December.

Leafminers: Adult leafminer activity remains low in all areas, about average for this time of season.