Seasonal Reinvasion Drives DBM Pressure in Desert Vegetables
Diamondback moth (DBM), Plutella xylostella, is a recurrent pest in desert vegetable systems due to annual fall reintroduction, not local persistence. Area-wide trapping data show populations decline to near zero during summer months, followed by re-establishment associated with transplant movement and seasonal conditions (Fig. 1). These populations often arrive with prior insecticide exposure, increasing early-season management complexity.

Can UV Light and Alyssum Improve Adult DBM Capture?
To evaluate whether behavioral cues—UV light and sweet alyssum—can enhance adult DBM attraction and improve early detection or interception prior to oviposition.

Testing UV Light and Alyssum in Field-Deployed Traps
Pheromone traps were deployed with UV light, sweet alyssum, or both. Adult DBM captures were recorded nightly across repeated sampling periods.

UV Light Dominates Capture; Alyssum Provides Additional Benefit
UV light significantly increased DBM captures, while sweet alyssum also enhanced attraction, though to a lesser extent (Figs. 2–3). No interaction between cues was detected, indicating independent effects.

Improving Early Detection and Interception within IPM Programs
These results show that adult DBM can be captured more effectively by using simple behavioral cues, especially UV light, with additional benefit from alyssum. In desert systems where populations are reintroduced each season, deploying these traps in transplant nurseries and along field edges could help remove adults before they lay eggs and contribute to new infestations. As part of an integrated pest management (IPM) program, improved trapping can support better scouting and more precise timing of control decisions. 

Figure 1. Seasonal DBM trap captures from Dr. John Palumbo’s area-wide trapping
network illustrating summer population collapse and fall reintroduction in desert
systems. 


Figure 2. Mean adult DBM captures per night with and without UV light (± SE) 


Figure 3. Mean adult DBM captures per night with and without sweet alyssum (± SE) 

Early Sunday morning, 11 May 2025 Dr. John Palumbo passed away at his home in Yuma, AZ. John was an excellent scientist and educator, a lifelong student who truly enjoyed good work and a full life. John was also a very good friend and colleague, not only to me but to the many with whom he worked and lived. We mourn his passing and miss him deeply.

I first met John in 1990 when he joined the faculty at the University of Arizona (UA) as an Assistant Professor and Extension Specialist in Entomology and Integrated Pest Management (IPM) based at the Yuma Agricultural Center (YAC). He came very highly recommended by Drs. Theo Watson and Leon Moore, who were research and Extension entomologists and former mentors of John’s when he was an undergraduate and graduate student at the UA.

John did his Ph.D. work at Oklahoma State University (OSU) under the direction of Dr. Larry Crowder, who had been on the UA faculty in entomology prior to moving to OSU. I am originally from Oklahoma and went to graduate school at OSU in agronomy and soil science. I used to jokingly tell John that having spent some formative years in Oklahoma was probably his time of refinement and saving grace.

John was a perfect fit for the position at the UA and at YAC; he was highly intelligent with an excellent background. Most importantly, it was very clear that he was enthusiastic about his opportunity, and he really wanted to do the work necessary. He truly loved his work, and he did it very well with passion and commitment.

John had an outstanding work ethic, he was a man of good character, and his integrity was exceptional. John was a practical realist, and even though we could both see and comment on the imperfections in the world around us, he did not whine or complain about things that could have been better. He was always an optimist, and he did the best with what he had, appreciated his opportunities, and he consistently did a great job with it. He was a model as a professional and as a good person. He had confidence in himself, but he was humble, and he always treated people with respect and dignity. Very importantly, John had a great sense of humor, and I could always count on that with him.

In 2018 John was diagnosed with stage 4 lung cancer. That was not a good prognosis, but John faced it with dignity and grace. John had access to some new drugs that helped give him a good quality of life that he sustained for seven years. In the past seven years he has been productive, worked hard, and he has had fun doing so. He did not dwell on the negative but always emphasized the positive.

John was an avid reader and we both shared an interest in history, particularly American history, including the Civil War. Many of our conversations centered around these common interests and we shared many good reading references.

In my readings I have also enjoyed the writings of Ernest Hemingway. Hemingway emphasized the value and benefits of living a robust life and spending time outdoors in nature. Many of his characters demonstrated a strong way of living and strength in facing the end of their lives. In one of Hemingway’s books (Across the River and Into the Trees) he offered a recounting of the passing of General Thomas “Stonewall” Jackson on 10 May 1863 following his injuries at the Battle of Chancellorsville.

Dr. McGuire, the attending physician, confirmed to Jackson what his wife had conveyed earlier regarding McGuire’s projection of his impending death that day. Jackson’s response after thinking for a moment was that the day was Sunday and he felt that Sunday was a good day to die. After passing in and out of delirium, the last he said was “Let us cross the river and rest in the shade of the trees.”

John Palumbo passed away on a Sunday in May. He has crossed the river and is now resting in the shade of the trees.

I’m excited to share an upcoming free webinar series from the Emerging Viruses in Cucurbits Working Group (EVCWG). For those readers who may be unfamiliar with this organization, the EVCWG is a collaborative partnership that works to promote virus research and communication across the cucurbit industry. It was established with support from the cucurbit industry and funding from the Southern Region IPM Center, a sister organization to the Western IPM Center, but works throughout the US and internationally. The EVCWG brings together members from academia, government, and private industry who work in research, production, extension, outreach, and regulation. The diversity of expertise, geographic locations, and industry connections help create more effective and practical strategies for identifying and controlling viral threats to US cucurbit production. With the lack of hard freezes this winter and pressure from key cucurbit vectors arriving early across Yuma County, you won't want to miss these upcoming informational sessions!

 

Upcoming Webinars
Aphid-, Beetle-, and Thrips-transmitted Viruses in Cucurbits
Wednesday, April 22, 2026 11:00 AM – 12:30 PM (Central Time)

This 1 hour and 20 minute session will cover key insect-vectored viruses affecting cucurbit production, including identification, transmission, and management strategies. Registration link: https://bit.ly/47DlDPi

Other Vectored and Mechanically- and Seed-transmitted Viruses and Viruses with Unknown Modes of Transmission in Cucurbits
Tuesday, May 5, 2026 11:00 AM – 12:00 PM (Central Time)

This one-hour webinar will explore additional virus transmission pathways and discuss emerging challenges in cucurbit virus management. Registration link: https://bit.ly/4rHHpbM

To learn more about the EVCWG and the resources they make available, please visit their homepage at: 
https://ecucurbitviruses.org/

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

Vegetable season is well underway and early planted vegetable crops are already about one month old. Many fields have or soon will need to be cultivated. As such, I thought it would be timely to “repost” this video on “new” technologies for cultivating weeds - 1) a camera-guided side-shift hitch and 2) finger weeders, an in-row weeding tool (Fig. 1). The video shows the device operating in seedling corn, but it will work similarly in other crops such as broccoli or cauliflower.

We have found the devices work well. Trials conducted in cotton over 3 years showed that use of camera-guidance improved weed control by more than 30% and finger weeders removed about 45% of the in-row weeds. Weed control using the two technologies together simultaneously was roughly 90% for broadleaf weeds and about 85% for all weed species including grasses.

If you are interested in trying these technologies, please contact me. We still have the equipment and I’d be happy to work with you.

Fig. 1. Technologies for precision cultivation and in-row weeding include a) a
camera-guided side-shift hitch attached to a cultivator and b) in-row weeding
tools (finger weeders).



Watch the Video Below

According to some authors "the human brain can process images up to 60,000 times faster than words"¹. So, I decided to share images of some of the onion herbicide tests we did at the Yuma Ag Center last season hoping you find them interesting as the season progresses. As you know the products tested could respond differently under different environments. Also some of these trials are done searching for new alternatives, therefore products are not registered.

 

1. https://www.linkedin.com/pulse/why-pictures-speak-louder-than-words-laura-nicole-brown#:~:text=According%20to%20Krista%20Neher%2C%20the,that%20really%20captures%20your%20attention.

Aphids are considered the most difficult to control insect pests in organic vegetables due to the lack of effective bioinsecticides as well as their ability to hide within plant structures. For instance, lettuce aphids normally hide in the head or heart of lettuce, making them difficult to reach by insecticide treatment or natural enemies. It is important to adopt other methods, such as nitrogen and water management, for additional aphid suppression.

As sap-sucking insects, aphids depend on the nutritional content of the sap ingested from the plant hosts for proper growth and development. Nitrogen availability is one of the most important factors in the development of aphid populations. Thus, limiting your nitrogen application to the optimum amount required for your crops is good practice for maintaining your aphid population below damaging level. Additionally, the use of slow-release (minimizing the risk of nutrient deficiency or excess) nitrogen fertilizer can be beneficial for aphid control. On the other hand, excess of nitrogen will make your crops a superfood for aphids. This accelerates the growth, development, and reproduction of the pests, reduces their generation time, and results in an increase in the number of generations and density during the cropping season. Excess of nitrogen particularly affects aphids on host crops such as lettuce, wheat, and sorghum. In some situations, high nitrogen levels in plant tissue can decrease resistance and increase susceptibility to aphids’ attacks. Applying the optimum amount of nitrogen fertilizer can tremendously help to manage aphids. In addition to pest management, effective fertilizer usage can also result in economic and environmental benefits.

Selected References:
1- Altieri, M. A., C. I. Nicholls, and M. A. Fritz. Manage insects on your farm: a guide to ecology strategies. SARE. https://www.sare.org/resources/manage-insects-on-your-farm/

2- Aqueel, M. A., and S. R. Leather. 2011. Effect of nitrogen fertilizer on the growth and survival of Rhopalosiphum padi (L.) and Sitobion avenae (F.) (Homoptera: Aphididae) on different wheat cultivars. Crop Protection. 30:216-221.

3- Bal, R., M. Groshok, and Y. Jama. 2024. Effects of nitrogen and potassium-based fertilizers on green peach aphid and abundance and arugula condition and growth. The Scientist. 6:1. https://journals.mcmaster.ca/iScientist/article/view/2931

4- Sinha, R., B. Singh, P. K. Rai, A. Kumar, S. Jamwal, and B. K. Sinha. 2018. Soil fertility management and its impact on mustard aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae). Cogent Food & Agriculture. 4: 145094.

5- Xia, C., W. Xue, Z. Li, J. Shi, G. Yu, and Y. Zhang. 2023. Presenting the Secrets: exploring endogenous defense mechanisms in chrysanthemums against aphids. Horticulturae. 9: 937. https://doi.org/10.3390/horticulturae9080937

Supplying the optimum amount of water to your crop is also very important for effective pest control. Water availability around plant roots increases nitrogen absorption. Additionally, with high water availability, there is an increase in phloem pressure, making food more accessible to sap-sucking insect pests. Supplying the required amount of water using appropriate irrigation methods and irrigation scheduling can be beneficial for pest management. Although these practices will not completely prevent infestation of aphids, they can surely play a role in reducing the density of aphid populations on your crops.

In the arid farming systems of Yuma, Arizona, growers often face the challenge of sustaining soil health and productivity between intensive winter vegetable cropping seasons. One effective, science-backed strategy to support this transition period is the use of Sudan grass (Sorghum Sudanese) as a summer cover crop (Figure 1).

Sudan grass grows rapidly in hot, dry conditions, making it well-suited for our desert climate. Its value extends beyond simple ground cover; this warm-season annual plays a pivotal role in enhancing long-term soil health, improving field conditions, and supporting environmental resilience.

Figure 1. Sudan grass in the Valley Research Center at the University of Arizona, Yuma
Agricultural Center, Yuma, Arizona.

Soil Health Benefits

Sudan grass contributes significant organic biomass, which boosts soil organic matter and fuels microbial life (USU Extension, 2020). Its deep root system also improves soil structure by loosening compacted layers and enhancing water infiltration (Advance Cover Crops, 2021).

Natural Weed and Disease Suppression
Its dense canopy shades out summer weeds, while allelopathic compounds such as sorgoleone help suppress soil-borne pathogens (SARE, 2012). As a rotation crop, Sudan grass disrupts pest and disease cycles common in lettuce systems, including Fusarium wilt (UVM Extension, 2010).

Environmental and Water Efficiency
As a living cover, Sudan grass reduces dust, protects against erosion during monsoon events, and uses water efficiently compared to cash crops (Arizona Forage and Grain, 2015).

Economics and Future Crop Performance
Though not a direct income generator, Sudan grass has low input requirements and can be used as forage if needed (UMN Extension, 2020). Importantly, it leaves behind a biologically enriched soil bed that benefits subsequent crops like lettuce, often resulting in better stands and vigor (USU Extension, 2020)

Bottom Line
Sudan grass offers growers in the desert Southwest a strategic tool to enhance their production systems while supporting sustainability. By bridging the gap between seasonal crops, it transforms summer downtime into an investment in soil productivity and environmental stewardship.

VegIPM Update Vol. 17, Num. 8
April 15, 2026

Results of pheromone and sticky trap catches below!!

Corn earworm:  CEW numbers remained steady at most locations over the last two weeks, high numbers continue to be seen at Welton and Tacna areas. CEW is active throughout the summer and high numbers are expected leading into the next produce season.

Beet armyworm: BAW activity remained steady over the last two weeks. Historically adult BAW is collected through the summer, although numbers are lower compared to Mar-Apr seasonal highs.

Cabbage looper:  Cabbage looper moth activity continued to decrease over the last two weeks. Numbers are expected to continue decreasing as temperature gets warmer.    

Diamondback moth: Adult DBM numbers decreased across most locations. Based on other years data, DBM numbers are expected to continue decreasing as cole crops acres decrease.  

Whitefly: Adult remains steady across all locations, about average for this time of year. Expect numbers to continue increasing as temperatures warm up.  

Thrips: Thrips activity remains steady across locations. Historically, WFT numbers peak in May.  

Aphids: Winged aphid numbers continued to decrease at most sites in the last two weeks. Winged aphids disappear from our traps after April as temperatures become too hot for aphids.  

Leafminers: Adult leafminer activity decreased over the last collection. Leafminers are collected in our traps throughout the summer.