University of Arizona Extension is offering two in-person CEU events at the Yuma Ag Center to help PCAs lock in their hours before the season hits full swing:

Fall IPM Update
Date: Tuesday, August 12
Time: 7:00–10:00 AM
Location: Yuma Agricultural Center
Credits: 2 AZDA | 2 CA DPR | 2 CCA (approved)
This session will cover current IPM issues in desert vegetable crops. Breakfast will be provided. Please RSVP to help us plan for food by emailing Robert Masson: masson@arizona.edu

2025 Laws & Regulations Update
Date: Wednesday, September 3
Location: Yuma Agricultural Center
Credits: 4 CA DPR Laws (requested) | AZDA hours pending
This session will focus on pesticide laws, safety, and compliance updates relevant to licensed PCAs.

Take advantage of these local opportunities to complete your CEUs before the season gets into full swing.

If your schedule doesn’t allow for in-person attendance, UA Extension also offers online, on-demand CEU videos so you can earn credits at your convenience. You can find them here: Continuing Education Units | UA Cooperative Extension

Water and nutrient demands coincide with the fruiting cycle of most crop plants. The efficient management of irrigation water and plant nutrients is enhanced by tracking crop development in the field and making decisions on plant demand and condtion. The use of heat units (HUs) with 86/55 oF upper and lower thresholds can be applied to warm season crops in the desert Southwest in relation to the thermal environmental impacts on the development of all crop systems (Brown, 1989), including chiles, (Figures 1 and 2).

Crop Phenology Relationship to Water and Nitrogen Demand
Phenological guidelines have been developed for many crops, including New Mexico (NM) type chiles (Soto-Ortiz and Silvertooth, 2007 and Silvertooth, et al, 2010; Figure 1). This phenological guideline can be used to identify or predict important stages of crop development that impact physiological requirements. For example, a phenological guideline can help identify stages of growth in relation to crop water use (consumptive use) and nutrient uptake patterns (Figure 3).

This information allows growers to improve the timing of water and N inputs to improve production efficiency. For most crops HU based phenological guidelines can be used to project critical dates such as harvest or crop termination. Many other inputs and applications related to crop management (e.g., pest management) can be derived from a better understanding of crop growth and development patterns.

Arizona chile production, consisting of NM type chile varieties, is mostly located in Cochise County in southeastern Arizona. The 2025 Arizona chile crop has been progressing steadily in line with the basic phenological model shown in Figure 2. For a set of fields near Pearce, Arizona with several different NM type varieties and planting dates ranging from 2 – 22 April 2025, current heat unit accumulations after planting are 1,785 – 1,957 (Figure 4a-d). The crop is moving into peak bloom and the period of peak N and water demand.

This is very good time in the season to evaluate these fields in relation to current irrigation and N fertilization needs.

Figure 1. Typical relationship between the rate of plant growth and development and
temperature. Growth and development ceases when temperatures decline below the
lower temperature threshold (A) or increase above the upper temperature threshold (C).
Growth and development increases rapidly when temperatures fall between the lower
and upper temperature thresholds (B).


Figure 2. Basic phenological guideline for irrigated New Mexico-type chiles.


Figure 3. Basic phenological guideline for irrigated New Mexico-type chiles with periods
of peak water and nutrient demand, including optimum N application window.


Figure 4a. New Mexico type chile, variety Carne Duro, 31 July 2025.


Figure 4b. Crown set chiles, Carne Duro variety, 31 July 2025.


Figure 4c. Early fruit set, Carne Duro variety, 31 July 2025.


Figure 4d. Mid-canopy fruit set, Carne Duro variety, 31 July 2025.

References

Brown, P. W.  1989. Heat units.  Bull. 8915, Univ. of Arizona Cooperative Extension,
College of Ag., Tucson, AZ.

Silvertooth, J.C., P.W. Brown, and S. Walker.  2010.Crop Growth and Development for
Irrigated Chile (Capsicum annuum).  University of Arizona Cooperative Extension
Bulletin No. AZ 1529

Soto-Ortiz, R. and J.C. Silvertooth.  2007. A Crop Phenology Model for Irrigated New
Mexico Chile (Capsicum annuum L.) The 2007 Vegetable Report. Jan 08:104-122. 

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Meerkat’ was seeded, then sprinkler-irrigated to germinate seed Jan 13, 2025 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂ backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.

Downy mildew (caused by Peronospora farinosa f. sp. spinaciae)was first observed in plots on Mar 5 and final reading was taken on March 6 and March 7, 2025. Spray date for each treatments are listed in excel file with the results.

Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft²areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft²area of bed was approximately 144. The percentage were then changed to 1-10scale, with 1 being 10% infection and 10 being 100% infection.

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided most effective control against the disease include Orondis ultra, Zampro, Stargus, Cevya, Eject .Please see table for other treatments with significant disease suppression/control.  No phytotoxicity was observed in any of the treatments in this trial.

It is with sadness and a sense of loss that we share the news that our friend and colleague, John Palumbo passed away last weekend. John and I have been office mates so to speak, only two doors apart, for the past 17 years. What I will miss most about John is his presence. Warren Buffet said that a key to becoming a better person was to surround yourself with people that are better than you. In other words, hangout with people who had traits and characteristics that you admire and want to emulate. John was one of those people. He made you want to be a better person. We will miss you, John. RIP.

My name is Mazin Saber, and I serve as an Associate in Extension specializing in Weed Management at the School of Plant Sciences, University of Arizona/Yuma County Cooperative Extension, based at the Yuma Agricultural Center. My work focuses on developing innovative site-specific weed management strategies tailored to specialty crop systems in desert agriculture, aiming to establish effective and sustainable weed control programs. I currently lead a new weed control research initiative at the Yuma Agricultural Center.

My academic background includes a Bachelor’s degree in Agricultural Mechanization and a Master’s degree in Agronomy from the University of Basrah, Iraq. I also hold an M.E., and Ph.D. in Agricultural and Biological Engineering from the University of Florida, where my doctoral research focused on designing automated mechanical intra-row weed control system for row crops.

Previously, my research has involved quantitative assessment of crop water-use and salt balance in the Lower Colorado River region. By utilizing advanced tools such as Eddy Covariance to measure evapotranspiration across 14 major crops over multiple seasons on commercial farming, I have contributed to improving water use efficiency and enhancing the sustainability and competitiveness of desert agriculture.

As I build my weed management program, I am conducting an assessment survey to identify the most pressing weed management challenges. Your feedback is crucial to ensure this program meets your needs. Please take a few minutes to complete the survey using the link below.

https://uarizona.co1.qualtrics.com/jfe/form/SV_4Od09r4hPLThLz8

I am available for any discussions about weed issues on your farm and I am happy to arrange field visits or ride-alongs to better understand your specific challenges. Please feel free to reach out to me directly.

Email Mazin

As the desert vegetable season ramps up, organic growers face tough pest management challenges with limited insecticide options. To help address this, University of Arizona researchers at the Yuma Agricultural Center conducted field trials during the 2024–2025 season, testing OMRI-listed products on six key pests in leafy greens and Brassicas.

This article highlights results for products like Entrust, Pyganic, XenTari, and M-Pede, evaluated for their performance against diamondback moth, beet armyworm, whiteflies, green peach aphid, pale striped flea beetle, and western flower thrips. The results can help growers fine-tune their spray programs and make more informed decisions this season.

Click here to read the full report: Organic-Allowed Insecticide Options for the Management of Six Major Insect Pests in Arizona’s Vegetable Crops

As lettuce season approaches, irrigation management becomes critical for maintaining optimal soil moisture levels in the active root zone. Proper irrigation not only supports healthy crop growth but also prevents excessive water applications that can lead to nitrate leaching, an issue of both environmental concern and economic loss. Likewise, under-irrigation can reduce nitrogen uptake, as adequate soil moisture is essential for root absorption. This is especially critical in an extremely dry region like Yuma, where maintaining optimal soil moisture directly impacts both water and nitrogen use efficiency. This article provides an in-depth guide for growers on how to schedule irrigation based on crop growth stage, system type, and current weather conditions. The article introduces updated crop coefficient (Kc) values developed specifically for Yuma lettuce production through recent field research led by Drs. Sanchez and French, in partnership with Yuma Center of Excellence for Desert Agriculture (YCEDA). It also explains how to use the Arizona Meteorological Network(AZMET) and other practical evapotranspiration tools to make irrigation decisions more precise and site-specific.

Combining updated Kc values, local reference ET data, and irrigation efficiency concepts, this resource empowers growers to improve water use efficiency and sustain high yields and enhance different cropping systems in the region.

Click this link to read the full article: Estimating Crop Evapotranspiration Using Lettuce Crop Coefficients for Irrigation Scheduling in Yuma, Arizona.

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.