This year tested the Ag Center in ways we weren’t prepared for, but it showed us how resilient we are. John’s team and the Palumbo Transition Team carried his work forward with the dedication he taught us, and Samuel and team kept the farm operating after Bert’s retirement.

And through it all, industry opened its arms to our new faculty and staff, turning what seemed like an almost impossible season into one we could navigate together.

I’m ending the year with gratitude for an IPM community that works together to keeps this program thriving.

Our next newsletter will be Jan. 7th 2026. Looking forward to what Volume 17 will bring!

To contact Macey Keith go to: maceyw@arizona.edu

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).

Among the diseases affecting global date palm production, trunk rot caused by Thielaviopsis spp. stands out as one of the most destructive and cryptic. That it because this broadhost necrotrophic fungus wreaks havoc on the tissues of palms but often shows no foliar symptoms until the tree is ready to collapse and is firmly beyond saving. Thriving in both arid and semi-arid production systems, Thielaviopsis trunk rot (TTR), also known as black scorch when it attacks foliage and flowers, can be problematic in the date palm production regions of the southwest and of landscape palms across the broader United States.

TTR, also called Medjnoon or Fool’s disease, is primarily caused by two related species of fungi from the genus Thielaviopsis. These fungal pathogens can affect a wide range of palm species, including true date palms (Phoenix dactylifera), Canary Island date palms, and other ornamental palms commonly used in urban landscaping. The disease can affect all palm tissues, and the tissue affected is determined by where the spores opportunistically meet an open wound of the host and begin their infection.

Once inside the palm, the fungus secretes an impressively diverse array of plant cell degrading enzymes before parasitizing and eating the tissue it kills. In trunk infections, TTR often leaves behind nothing but the tough, lignified, fibrous vascular bundles (see Figure 1), severely compromising the structural integrity of the palm and causing it to become crooked, collapsed, or to break off entirely often with little warning. Consequently, this can be extremely hazardous to any objects, equipment, or persons unlucky enough to be below the tree at the moment of collapse.

Figure 1: The trunk of a collapsed date palm. Only the thin, flexible fibrous bundles
remain, while other stabilizing trunk tissue has degraded to the point of snapping under
the weight of its own canopy.

In Arizona, there are no pesticides registered for use in edible-date palm production that show curative action once an infection is established. That makes preventative measures the primary choice when managing this disease. Because wounds are necessary for trunk infections, take note of potential sources of injury and where they arise. Trunk cracking due to excess water uptake, insect feeding damage, bird pecking, debris from windstorms, and mechanical damage from human activity are a few of the many sources of injuries associated with Thielaviopsis infection. Injury should be minimized, especially when other stressors are present with the host. Intentional wounds can be treated with copper solutions to deter the successful germination of the pathogens spores, but ensure the copper is present before the spores arrive and for the duration that the wound is fresh and not yet corked over.

Spores of these fungi survive both as resting structures in the soil and on dead palm debris. Spores can be moved from infected trees or residues to healthy trees by wind and rain splashing as well as pests moving from tree to tree. Infected trees should be removed as soon as possible after infection is confirmed, and infected remains should not be composted or recycled as mulches. Spores can also be moved mechanically on contaminated implements shared between trees. This makes the disinfection of tools and spikes vitally important to minimizing spread from infected trees to healthy trees.

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)

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

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. 

Area-Wide Insect Trapping Network—SUMMER EDITION

As something new this season, we will continue sharing thrips and whitefly counts throughout the summer months. Since these data are already being collected as part of our ongoing monitoring efforts, we felt it would be valuable to provide this information to stakeholders managing summer crops in the region.

VegIPM Update Vol. 17, Num. 10
May 13, 2026

Results of sticky trap catches below!!

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

Thrips: Adult thrips activity increased across locations over the last two weeks. Historically, western flower thrips numbers peak in May.