Next Wednesday we will host a whitefly CEU meeting at YAC. Details for meeting are below.

Date: Wednesday, June 17th
Time: 7:00am-9:15am
Location: U of A Yuma Ag. Center
6425 W. 8th St., Yuma, AZ, 85364
Breakfast burritos will be provided, please email me, maceyw@arizona.edu to RSVP.

Aso, mark your calendars for Tuesday, July 14th when we will host the Vegetable Pest Losses workshop, more details to come.

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).

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 

 

Since last season, there have been several new developments in commercial automated thinning and weeding technologies. Companies that focused primarily on weeding 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 including improved speed, durability and the ability to spot spray inter-row weeds. Arizona Cooperative Extension is in the process of organizing the Automated Thinner and Weeder Technologies Roundup, a field day where these technologies will be demonstrated operating in the field. NEW for this year will be that demos will be at the field scale level (> 1 acre) so attendees will have the opportunity to more fully evaluate machine performance and have time to visit with company representatives. The event will be held November 13th at the Yuma Agricultural Center in tandem with the Desert Difference Ag Connect Event. We would like to showcase as many innovative technologies as possible, so please contact me if you are interested in demoing your thinner/weeder or know someone that is. It’s an open invitation - private companies, university and government researchers are all welcome!

Fig. 1. Previous University of Arizona, Cooperative Extension AgTech Field Day Events
held at the Yuma Ag Center.

 

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. 

Results of pheromone and sticky trap catches can be viewed here.

 

Corn earworm: CEW moth counts remain at low levels in all areas, well below average for this time of year.

Beet armyworm: Trap increased areawide; above average compared to previous years.

Cabbage looper:  Cabbage looper counts decreased in all areas; below average for this time of season.

Diamondback moth: DBM moth counts decreased in most areas. About average for this time of the year.

Whitefly: Adult movement beginning at low levels, average for early spring.

Thrips: Thrips adult counts reached their peak for the season. Above average compared with previous years.

Aphids:  Aphid movement decreased in all areas; below average for late-March.

Leafminers: Adults remain low in most locations, below average for March.