John and I started our faculty careers just months apart more than three decades ago—he in vegetables and melons, me in cotton. We were forged in the same crucible: a time of intense agricultural crisis, stakeholder pressure, and institutional upheaval. We bore the same scars. That shared experience bound us in a special way, even as our day-to-day paths often diverged. Like the sun and moon, our seasons rarely overlapped—but when they did, we moved in rhythm, able to pick up conversations months later as if no time had passed. That was John: steady, grounded, always ready with insight, and always above the noise.

Over the years, we collaborated on critical efforts—most notably on resistance management for whiteflies, a challenge that demanded cross-commodity solutions. With John’s vision and leadership, we built voluntary stewardship agreements that are still in use a quarter-century later. More recently, we corresponded on a new tool to help growers manage resistance in real time—an app we’ll launch later this year. I had hoped he would be part of its rollout; his voice would have carried it far. Now, we will try to carry it forward in his spirit: practical, generous, and unwaveringly committed to growers.

This very newsletter—Vegetable IPM Updates—was John’s idea, and it thrived under his tireless dedication for decades. It was his way of connecting directly with those he served, every other Wednesday without fail. As we continue this tradition, we invite you to pause and reflect on how John and this newsletter may have touched your life or work. We honor him best by continuing to share the kind of clear, grounded, and useful information he believed in. We all know—that’s what John would have wanted.

-By Peter C. Ellsworth

Chile (Capsicum annuum) is an important crop in the desert Southwest. The Capsicum annuum species is the most common group of chiles that we encounter and these chiles are common in our southwestern diet. The New Mexico type chile (aka, Anaheim) is the most common type of chile crop in the desert Southwest including production ares in southeastern Arizona, southern New Mexico, west Texas, and northern Chihuahua, Mexico.

There are five domesticated species of chile peppers. 1) Capsicum annuum is probably the most common to us and it includes many common varieties such as bell peppers, wax, cayenne, jalapeños, Thai peppers, chiltepin, and all forms of New Mexico chile. 2) Capsicum frutescens includes malagueta, tabasco, piri piri, and Malawian Kambuzi. 3) Capsicum chinense includes what many consider the hottest peppers such as the naga, habanero, Datil, and Scotch bonnet. 4) Capsicum pubescens includes the South American rocoto peppers. 5) Capsicum baccatum includes the South American aji peppers (Guzman and Bosland, 2017). Some examples are shown in Figure 1 and some other chile pepper species as well.

Figure 1. Capsicum annuum pod types include A) Asian, B) Cayenne, C) Chile de Arbol,
D) Chiltepin, E) Hungarian Paprika, F) Jalapeño, G) New Mexican, and H) Poblano. A
Capsicum baccatum pod type is I) Aji. Capsicum chinense pod types are J) Bhut Jolokia,
K) Habanero, and L) Scorpion. A Capsicum pubescens pod type is M) Rocoto and a
Capsicum frutescens pod type is N) Tabasco. Source: Guzman and Bosland, 2017.

Crop Phenology
Understanding of the basic stages of plant growth in relation to time or age (crop phenology) and basic crop needs, i.e., water and nutrients, is an important part of crop management. There is a strong relationship among the phenological, morphological and physiological changes that occur with crop development. Understanding what is going on physiologically within a plant at various stages of growth and development is critical in efficiently managing crop inputs such as water and plant nutrients.

Plants respond to environmental conditions and temperature is the primary developmental force in plant development when water is not limiting. Heat units (HUs) can be used as a good measure of “thermal time” that drives plant development. Thus, HUs can be used as a management tool for predicting and identifying stages of growth and physiological needs. We can then use that information for more efficient timing of irrigation and nutrient inputs to crop and pest management strategies. Figures 2 and 3 describe the basic HU concept with upper and lower thresholds.

Crop phenology models describe how crop growth and development are impacted by weather and climate and provide an effective way to standardize crop growth and development among different years and across many locations (Baskerville and Emin, 1969; Brown, 1989).

People still use days after planting to estimate stages of crop development but HUs are more accurate and reliable. As a result, HU based methods of predicting and tracking crop growth can be more consistently and effectively used in crop production systems.

The use of HU-based phenology models is most applicable in irrigated crop production systems where water is a non-limiting factor. Water stress will alter phenological plant development and it is a major source of variation irrespective of temperature conditions.

Chiles are a warm season, perennial plant with an indeterminant growth habit that we grow and manage as an annual crop. The fruiting cycle begins at the crown stage of growth (Figures 4 and 5) and continues until the plant reaches a point of “cut-out” with a hiatus in blooming as the plant works to mature the chile fruit that the crop has set and established.

Figure 6 describes the basic phenological baseline for New Mexico – type chile and was developed from field studies conducted in New Mexico and Arizona (Silvertooth et al., 2010 and 2011; Soto et al., 2006; and Soto and Silvertooth, 2007).

Heat units accumulated after planting (HUAP) for any date of planting to the present date can be easily accessed in the Arizona Meteorological Network (AZMET) website.

https://azmet.arizona.edu/

In the 2025 season, New Mexico-type chiles in southeastern Arizona experienced a good start to the season after planting. In tracking a set of New Mexico-type chile varieties, their development is tracking very closely to the HU model shown in Figure 6. For example, crown formation and first flowers have been consistently observed at approximately 1,300 – 1,450 HUAP among numerous New Mexico type varieties in southeastern Arizona this season. Many fields are progressing through peak bloom consistent with Figure 6 and early set fruit is maturing nicely as well.

Figure 2. Typical relationship between the rate of plant growth and development and
temperature. Growth and development cease 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 3. Heat unit calculation with the sine curve method using upper and lower
temperature thresholds (Brown, 1989). The 86/55 ºF thresholds are used, consistent
with most warm season crops.

Figure 4. Photo of a New Mexico chile plant with crown formation and the first fruiting
branch shown withing the red circle.

Figure 5. Photo of a New Mexico chile plant with crown formation and early first fruiting
branch development. Source: Courtesy of Mr. Ed Curry, Pearce, AZ.


Figure 6. Basic phenological guideline for irrigated New Mexico-type chiles.

References
Baskerville, G.L. and P. Emin.  1969.  Rapid estimation of heat accumulation from maximum and minimum temperatures. Ecology 50:514-517.

Bosland, P.W., E.J. Votava, and E.M. Votava. 2012. Peppers: Vegetable and spice capsicums. Wallingford, U.K.: CAB Intl.

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

Guzmán, I. and P.W. Bosland. 2017. Sensory properties of chile pepper heat - and its importance to food quality and cultural preference. Appetite, 2017 Oct1;117:186-190. doi: 10.1016/j.appet.2017.06.026.

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

Silvertooth, J.C., P.W. Brown and S. Walker. 2011. Crop Growth and Development for Irrigated Chile (Capsicum annuum). New Mexico Chile Association, Report 32. New Mexico State University, College of Agriculture, Consumer and Environmental Science.

Soto-Ortiz, Roberto, J.C. Silvertooth, and A. Galadima. 2006.  Crop Phenology for Irrigated Chiles (Capsicumannuum L.) in Arizona and New Mexico. Vegetable Report, College of Agriculture and Life Sciences Report Series P-144, November, University of Arizona.

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

To better support our stakeholders with pest management, we are launching an Insecticide Resistance Monitoring Program in Calvin’s Lab. This initiative will include seasonal insecticide efficacy bioassays using the most commonly used insecticides. We will target key pests of major crops grown in Arizona, with a particular focus on those affecting vegetables and citrus crops.

A major goal of this program is to establish baseline susceptibility data for Plinazolin’s target pests in vegetables and citrus crops. This will enable us to monitor potential changes in susceptibility over time and make informed, timely adjustments to pest control strategies.

Insecticide resistance monitoring is a critical component of Integrated Pest Management (IPM). Understanding the baseline susceptibility of insect pests is essential for early detection of resistance and the long-term success of new insecticide modes of action. It is especially important to gather this data for Plinazolin before its widespread adoption in our region.

To support this effort, we will collect insects from vegetable- and citrus-growing regions throughout Arizona. Your collaboration is essential. We will reach out to request access to field sites where we can collect target insect populations. Additionally, we encourage you to contact us directly if you experience insecticide control failures or suspect resistance in your fields.

Our current target pests include:

• Diamondback moth

• Beet armyworm

• Cabbage looper

• Western flower thrips

• Citrus thrips

• Aphids

• Whiteflies

 

Please let us know if there are additional pests you would like us to consider.

Thank you for your continued support. We look forward to working with you to address Arizona’s most pressing pest management challenges.

In Yuma's arid agricultural landscape, selecting the right cover crops can significantly influence soil health, water management, and overall sustainability. Two notable options gaining attention among growers are Sudan grass and Sesbania. Sudan grass, a warm-season annual grass, is widely valued in Yuma for its ability to rapidly establish, providing excellent soil protection against erosion and wind. Its extensive root system enhances soil structure, boosts organic matter, and improves moisture retention, crucial for subsequent crops grown in desert conditions. Sesbania, a fast-growing legume, offers additional benefits. It excels at fixing atmospheric nitrogen, naturally enriching the soil and reducing the need for synthetic nitrogen fertilizers. Its deep taproot system penetrates compacted soil layers, improving water infiltration and reducing salinity levels, a common challenge in Yuma's agriculture.

Which Cover Crop Should You Choose?
The decision between Sudan grass and Sesbania depends largely on specific farm goals and challenges. If rapid establishment, erosion control, and increased organic matter are primary concerns, Sudan grass is an excellent choice. However, if the goal is to address soil fertility, nitrogen fixation, and salinity issues, Sesbania may be more beneficial. Using either Sudan grass or Sesbania as a cover crop in Yuma promotes healthier soils and supports sustainable farming practices, benefiting growers economically and environmentally. Considering these cover crops can be a strategic move toward enhanced agricultural productivity and long-term soil health in the region.

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

Corn earworm: CEW moth counts down in all traps over the last month; about average for December.

Beet armyworm: Moth trap counts decreased in all areas in the last 2 weeks but appear to remain active in some areas, and average for this time of the year.

Cabbage looper: Moths increased in the past 2 weeks, and average for this time of the season.

Diamondback moth: Adults increased in several locations last, particularly in the Yuma Valley most traps.  Below average for December.

Whitefly: Adult movement remains low in all areas, consistent with previous years 

Thrips: Thrips adult movement continues to decline, overall activity below average for December.

Aphids: Winged aphids still actively moving but declined movement in the last 2 weeks. About average for December.

Leafminers: Adult activity down in most locations, below average for this time of season.