The University of Arizona Vegetable IPM team is dedicated to delivering science-based solutions that help desert vegetable growers protect yield and quality while reducing reliance on broadly toxic pesticides. This mission comes to life each year through the Lettuce Insect Losses & Insecticide Use Workshop, where PCA surveys provide a snapshot of pest management practices across the desert.

At this year’s Lettuce Insect Losses & Insecticide Use Workshop, survey results continue to show the industry’s steady shift toward selective, reduced-risk products, while still relying on broad-spectrum tools when necessary. Paired with intensive scouting—nearly four visits per week—this approach allows PCAs to make smarter, more sustainable decisions that protect both crops and the environment.

Bottom Line: Twenty years of lettuce IPM research have given us stronger tools and smarter choices. Advances in chemistry, combined with the leadership of experts like Dr. John C. Palumbo have built grower confidence to lead with selective, reduced-risk products—protecting today’s lettuce crops while sustaining the tools we depend on for the future.

Figure 1. Survey results from the Lettuce Insect Losses & Insecticide Use Workshop
show total desert lettuce acreage treated with insecticides across three broad categories
of toxicity and selectivity: reduced-risk/selective, broad-spectrum, and broadly toxic.

CEU Event Coming 9/3
Don’t let the season slip by without meeting your CA and AZ PCA license requirements—UA Extension will host one more major session before the season heats up.The meeting will cover the highly desired Laws and Regs CA DPR category, giving you the chance to finish your renewals before the first pest outbreak of the season (hopefully). Details below:

2025 Laws & Regulations Update
Date: Tuesday, September 3
Location: Yuma Agricultural Center
Credits: 4 CA DPR Laws (requested) | AZDA hours pending
Time: 10:30a-3:30p

Agenda can be found HERE. We will need a headcount for lunch, please RSVP to Macey via email (maceyw@arizona.edu) or text (928-580-5785). 

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

Soils with excess soluble salts, saline soils, and/or excess sodium Na⁺ concentrations (sodic) are a natural feature of desert soils and common in arid land agriculture. This is primarily due to an accumulation of soluble salts near the soil surface as water evaporates from and the process is driven largely by the intense evaporative demand from the arid desert environment.

A saline soil is a problem in crop production systems because of the sensitivity of crop plants to salinity, although plants vary in their degree of sensitivity. The period of greatest plant sensitivity to salinity is in the early stages of development, during germination and stand establishment.

A sodic soil is a problem in crop production systems because of the adverse effects of excess sodium on soil structure, causing a dispersion of soil particles and the breakdown of soil aggregates. This leads to poor water infiltration and percolation in the soil profile.

The development of saline and sodic conditions does not happen rapidly; the symptoms are commonly slow and hard to see in their development, until they are a problem. Thus, two things are important for field management: 1) regular soil samples and 2) field observations of crop and soil conditions.

Some fundamental points regarding the management of saline and/or sodic soils are outlined in the following section.

1. A saline soil by definition has an electrical conductivity of the soil solution (extract, EC_e) of EC_c ≥ 4 dS/m. Functionally and practically, saline soils have sufficient soluble salts to interfere with and diminish plant growth and development.

a. Soil salinity is a relative term or condition based on the critical salt sensitivity levels of the crop plant in question.

b. Plants vary tremendously in their degree of salt tolerance.

c. Reclamation and management of soil salinity requires an understanding of the specific level of sensitivity of the target plant to salinity.

d. Saline soils commonly have good soil aggregation and structure.

e. Reclamation of saline soils requires sufficient water to accomplish leaching and the removal of soluble salts. Thus, good internal soil drainage is important.

2. Sodic soils have a high level of exchangeable sodium (Na⁺) on the soil cation exchange complex (CEC). Sodic soils by definition have an Exchangeable Sodium Percentage, ESP > 15 of the soil CEC, or a sodium adsorption ratio, SAR > 13 from the soil extract (calculated).

• Sodic soils commonly have poor soil structure and aggregation due to the dispersed condition of soil particles caused by high concentrations of Na on the CEC.
• In practice, finer textured soils, e.g. clay, clay loam, silty clay loam, etc. with high clay content can develop sufficient dispersion and poor soil structure at ESP or SAR levels ~ 6-10. The ESP and SAR designations are general guidelines and not absolute.   

Sodic soil reclamation does require an amendment that will facilitate the chemical exchange of Na⁺, usually from a calcium (Ca²⁺) source, such as gypsum (CaSO₄).

3. Reclamation for saline soil requires additional irrigation water for leaching. Chemical amendments are not necessary for soluble salt removal.

An effective and straightforward method of calculating a leaching requirement (LR) can be calculated with the following equation that was presented by the USDA Salinity Laboratory (Ayers and Westcot, 1989).

Leaching Requirement (LR) Calculation: 

Where:

EC_w= salinity of the irrigation water, electrical conductivity (dS/m)

EC_e= critical plant salinity tolerance, electrical conductivity (dS/m)

4. Saline soils do NOT need amendments for reclamation or management. Only leaching is needed.

5. Sodic soil reclamation involves a two-step process:
    1) Exchange of Na with Ca and
    2) leaching of soluble Na+ from the crop root zone.

6. Adequate soil leaching is required in both cases of saline and sodic soils.
a. In the case of sodic soil reclamation, the leaching needs to occur after appropriate amendment applications for Na⁺exchange with a suitable cation such as Ca²⁺.

7. Adequate drainage is necessary to accomplish sufficient leaching of solutes through the soil profile and below the root zone in the reclamation of both saline and sodic soils.

8. Irrigation systems capable of delivering sufficient water for leaching are necessary.

• Level basin flood irrigation best serves salinity leaching requirements.
• Sufficient salinity leaching can be accomplished with furrow flood or overhead sprinkler irrigation.
• Drip irrigation systems much be designed to provide sufficient volumes of water to accomplish adequate soil leaching.
  — Drip irrigation systems are commonly very limited in this respect.

9. Crop rotation systems are important in leaching and salinity management.

• For example: Crops planted on the flat and irrigated by level basin irrigation serves to facilitate good salinity leaching in a field.
• — Examples: wheat, alfalfa, sudangrass, etc.

10. Good field observations of crop growth and development in conjunction with regular soil and water sample analysis are key elements to the management of salinity and sodicity in agricultural fields.

For example, young plants in the germination and seedling stages of development are most susceptible to salinity and water stress. Abnormal amounts of seedling damage and/or difficulties in germination can often be early signs of increasing soil salinity.

Also, early signs of increasing salinity are often observed with plants demonstrating water stress with plant-available water levels in the soil that should seemingly be adequate for maintaining non-stressed plants.

Thus, fields that are showing signs of water stress and require irrigation in shorter intervals than usual can possibly be an early sign of increasing salinity and it is good to follow-up with a good set of soil samples and a sample of the irrigation water to check.

Early identification of problems in the field with increasing Na concentrations are commonly noticed with increasing tendencies of the soils in the field to form surface crusts very easily, which reduces water infiltration into the soil surface. This is often recognized at the time planting and stand establishment with germination problems resulting from increasing degrees of soil crusting.

11. As demonstrated by the LR calculation in point 3, water quality is an important factor in the management of soil salinity. The soil chemical environment will develop an equilibrium condition in relation to irrigation water quality (salinity content) and field management. The soil solution will have a definite chemical signature from the irrigation water being applied.

12. Soil drainage is an important factor in the management of soil salinity and sodicity. Good drainage is essential for the leaching and removal of soluble salts and the leaching and removal of excess sodium in the case of a sodic soil.

At events and in the halls of the Yuma Agricultural Center, I’ve been hearing murmurings predicting a wet winter this year…

As the Yuma Sun reported last week, “The storms of Monday, Aug. 25 [2025], were the severest conditions of monsoon season so far this year in Yuma County, bringing record-rainfall, widespread power outages and--in the fields--disruptions in planting schedules.”

While the Climate Prediction Center of the National Weather Service maintains its prediction of below average rainfall this fall and winter as a whole, the NWS is saying this week will bring several chances of scattered storms.

These unusually wet conditions at germination can favor seedling disease development. Please be on the lookout for seedling disease in all crops as we begin the fall planting season. Most often the many fungal and oomycete pathogens that cause seedling disease strike before or soon after seedlings emerge, causing what we call damping-off. These common soilborne diseases can quickly kill germinating seeds and young plants and leave stands looking patchy or empty. Early symptoms include poor germination, water-soaked or severely discolored lesions near the soil line, and sudden seedling collapse followed by desiccation.

It is important to note that oomycete and fungal pathogens typically cannot be controlled by the same fungicidal mode of action. That is why an accurate diagnosis is critical before considering treatments with fungicides. If you suspect you have seedling diseases in your field, please submit samples to the Yuma Plant Health Clinic or schedule a field visit with me.

National Weather Service Climate Prediction Center: https://www.cpc.ncep.noaa.gov/

National Weather Service forecast: https://forecast.weather.gov

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.

Hi, I’m Chris, and I’m thrilled to be stepping into the role of extension associate for plant pathology through The University of Arizona Cooperative Extension in Yuma County. I recently earned my Ph.D. in plant pathology from Purdue University in Indiana where my research focused on soybean seedling disease caused by Fusarium and Pythium. There, I discovered and characterized some of the first genetic resources available for improving innate host resistance and genetic control to two major pathogens causing this disease in soybean across the Midwest.

I was originally born and raised in Phoenix, so coming back to Arizona and getting the chance to apply my education while helping the community I was shaped by is a dream come true. I have a passion for plant disease research, especially when it comes to exploring how plant-pathogen interactions and genetics can be used to develop practical, empirically based disease control strategies. Let’s face it, fungicide resistance continues to emerge, yesterday’s resistant varieties grow more vulnerable every season, and the battle against plant pathogens in our fields is ongoing. But I firmly believe that when the enemy evolves, so can we.

To that end I am proud to be establishing my research program in Yuma where I will remain dedicated to improving the agricultural community’s disease management options and tackling crop health challenges. I am based out of the Yuma Agricultural Center and will continue to run the plant health diagnostic clinic located there. 

Please drop off or send disease samples for diagnosis to:
Yuma Plant Health Clinic
6425 W 8th Street
Yuma, AZ 85364

If you are shipping samples, please remember to include the USDA APHIS permit for moving plant samples.

You can contact me at:
Email: cdetranaltes@arizona.edu
Cell: 602-689-7328
Office: 928-782-5879

Thank you all very much. I look forward to meeting you all soon.

Biological control is a crucial tool for managing pests in organic crop production. Arthropod natural enemies provide significant ecosystem services that favor the suppression of agricultural insect pest populations. When you maintain permanent habitats and food sources for the natural enemies of pests in the vicinity of your farms, it favors the continuous availability of the natural enemies. When the growing season starts, the good bugs will be readily available to attack the pests before they become established in the crops. Planting a diversity of flowering plants (e.g., sweet alyssum, nasturtium, milkweeds, common cryptantha, hillside vervain, wild petunia, etc.) on a small portion of your farms or the farms border can provide adequate food and shelter allowing to maintain abundant and diverse natural enemy species, including syrphid flies, tachinid flies, lacewings, parasitic wasp, etc. that will attack aphids, thrips, lepidopterans, and more.  

Figure 1. Insectary plants planted in field margins to attract and conserve natural enemies.

Figure 2. Some suggested insectary plants. 

Intercropping, the practice of growing different crops in the same field, is also a suitable agricultural practice for managing insect pests because landscape diversity plays a crucial role in biodiversity conservation and sustainable pest management. Crops grown in intercropping systems are more likely to be less injured than those grown in monoculture. The non-host companion plants can have repellent or deterrent properties that act against insect pests that attack the main crop. Companion plants can also trap the pests, reduce their ability to locate the host plant, and increase the abundance of natural enemies. Like in a push-pull intercropping system, your main crop is intercropped with plant species that can make it less visible or can emit undesirable volatiles (smells) that divert the pests away from the main crop, on the other hand, other plants in your intercropping system can be extremely attractive using stimuli that are highly apparent and attractive to the pest, hence trapping the pest (Fig. 3). Insects use visual, chemical, or tactile cues to locate their host. Thus, by intercropping the main crop with plants that emit more attractive scents, which are more visually appealing, or can release undesirable odors to the pests, we can reduce the abundance and impact of the pest on the main crop.

Figure 3. Pictorial representation of push-pull strategy. 

In Brazil, the push-pull strategy has been found effective in managing major kale pests. They found that using mustard as a preferred host pulled the pests away from the kale crops, while marigold plants increased the beneficial arthropod population, which provided additional control of the pests. In Salinas, California, intercropping lettuce with sweet alyssum has favored some measurable aphid control. Sweet alyssum attracts and feeds hoverflies, which then lay eggs in lettuce, producing hoverfly larvae that consume aphids (Fig. 4).  

Figure 4. Graphical representation of Lettuce-Alyssum intercropping system for aphids
control. (Image source: Brannan 2013). 

As you plan for the next season, you can consider planting flowering plants along the borders of your farms or in dedicated patches to conserve natural enemies and enhance your biological control. When feasible, consider intercropping multiple crop species that are not affected by the same pests; this will reduce the abundance of insect pests and also increase the abundance and diversity of beneficial insects. 

Area-Wide Insect Trapping Network
Samuel Discua, Leo Chavez, and Javier Chavez
VegIPM Update Vol. 16, Num. 18
Sept. 3, 2025

Results of pheromone and sticky trap catches coming soon!!

Corn earworm:  CEW moth counts increased areawide; about average for this time of year.

Beet armyworm: BAW moth counts are up; below average compared to previous years.

Cabbage looper: Cabbage looper counts remain low in all areas; about average for this time of season.

Diamondback moth: A few DBM moths were caught in Dome and Yuma Valleys; consistent with previous years.

Whitefly:  Adult movement continues to increase, about average for this time of year.  

Thrips: Thrips adult activity remains low but continues to increase, about average for this time of year.

Aphids: Aphid movement is absent and consistent with what we typically see during the summer.

Leafminers: Adult activity increased across all locations, below averge for this time of year.