With the desert produce season almost completed and the spring melon season beginning, now is a good time to review the insecticide chemistries commonly used in your insect management programs. This is an important consideration as you make the transition from winter produce to alfalfa, spring melons and summer cotton where many of the same insecticide products are available in all these commodities.  Sustaining long-term insecticide efficacy that provides cost-effective crop protection requires a conscious effort on the part of PCAs and growers to use insecticides responsibly.  Over the past 30 years, Agrochemical Manufacturers have developed and brought to market over 20 new classes of chemistry that are highly effective, selective, and significantly safer than their chemical predecessors. These include the neonicotinoids, spinosyns, tetramic acid derivatives and anthranilic diamides to name a few.  Most recently, we have seen new feeding disruptor products, PQZ (pyrifluquinazon) and Versys/Sefina (afidopyropen) being applied to fall melons for virus management and in winter vegetables for aphid management. Although, the development of new insecticide chemistries has been a bit slow over the past few years, we’re now seeing industry beginning to develop several new experimental insecticides for desert crops. You’ll be pleased to know that several compounds are being targeted for western flower thrips. Of course, at best many of these products are a few years away from registration. But this is great news as many of the older products are slowly being phased out of the marketplace. It was just a couple of years ago that flubendiamide (Belt, Vetica) was removed from the market, chlorpyrifos (Lorsban) is now gone, and EPA is currently proposing label changes to the neonicotinoids which could impact their use on many important crops. Thus, it is imperative to sustain the efficacy of the newer insecticide tools currently available and Insecticide Resistance Management (IRM) is now more important than ever. The most fundamental approach to IRM is to minimize the selection of resistance by a pest to any one type of insecticide chemistry. The key to sustaining insecticide susceptibility is to avoid exposure of successive generations of an insect pest population to the same MOA. Historically, alternating, or rotating compounds with different modes of action (MOA) each time you spray has provided sustainable and effective IRM in our desert cropping systems.  When it is comes to IRM; “rotation, rotation, rotation”. In other words, never expose a generation of insects to the same MOA more than twice.  The Insecticide Resistance Action Committee (IRAC), a coordinated crop protection industry group, was formed to develop guidelines to delay or prevent resistance. Using their most recent information we have produced a brief publication which provides the latest local information on the modes of actions, routes of activity and pest spectrum for important insecticide chemistries used in desert produce and melon crops - see the attached Insecticide Modes of Action on Desert Produce Crops. This classification list will provide you with an additional set of guidelines for the selection of insecticides that can be used in desert IPM programs.

In arid and semi-arid regions, water is our first limiting factor in a crop production system, followed closely by bio-available nitrogen (N).  Thus, our management of water and N are critically important to produce a healthy crop with good yields and quality.
 
Water and nutrient demands coincide with the fruiting cycle and efficient management of irrigation water and plant nutrients is enhanced by tracking crop development in the field.  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 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 some crops or production situations HU based phenological guidelines can be used to project critical dates such as harvest or crop termination.  Many other applications related to crop management (e.g., pest management) can be derived from a better understanding of crop growth and development patterns.

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.

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. 

It’s been anything but a smooth Spring melon season this year. Mild winter temperatures have contributed to the persistence of weeds and whitefly populations culminating in high viral pressure observed from the very first melon plantings onward. Through a collaborative effort between the University of California, USDA, and University of Arizona we would like to invite growers, PCAs, farm managers, researchers, and other stakeholders from the desert melon production regions in California, Arizona, and Mexicali to join us for a stakeholder meeting to discuss field observations and disease management research priorities.  

This meeting will provide an opportunity to review this season’s observations and trends across production areas, hear research and strategy updates from plant pathology specialists, and, most importantly, create space for discussion among stakeholders to better understand what is happening and give input on the disease management research priorities you want to see pursued moving forward. Topics and invited speakers include:

• Bill Wintermantel (USDA-ARS) – Overview of cucurbit viruses affecting desert melon production
• Arun Babu (UCCE Imperial)– Whitefly populations and insecticide efficacy trials in Imperial Valley
• Samuel Discua (University of Arizona, Yuma) – Whitefly populations and insecticide efficacy trials in Yuma, Arizona
• Chris Detranaltes (University of Arizona, Yuma)– Viruses and other pathogens recovered from symptomatic melon plants in Yuma, Arizona
• Ana M. Pastrana (UCCE Imperial) – Viruses and other pathogens recovered from symptomatic melon plants in Imperial Valley, California

 

Meeting details:
Where: AgWest Imperial 485 Business Pkwy, Imperial, CA 92251
When: June 2, 2026 10:30 am – 12:30 pm (lunch to follow until 1:00 pm)

Lunch will be provided. Please register here if you plan to attend so we can have an accurate food count and seating estimate: Registration Survey

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 

Presentation given at 2021 ASABE Annual International Meeting on the development and evaluation of a novel, band steam applicator for controlling soilborne pathogens and weeds in lettuce. Band-steam is where steam is used to heat narrow strips of soil to levels sufficient to kill soilborne pathogens and weeds (140 °F for 20 minutes). Development of a band-steam applicator that applies steam in 4" wide by 2" deep band centered on the seedline is presented. Two trials investigating the use of band-steam for controlling Sclerotinia lettuce drop and weeds in lettuce were conducted. Trial results were promising. Highlights included finding that treatment with steam provided better than 85% weed control, and the unexpected result that crop yields were improved by more than 24%. Energy requirements were high and treatment costs were more than $650/acre. Band-steam may be a viable technique for controlling soilborne pests in high value vegetable crops such as lettuce if the significant yield increases found in this study can be realized.

To watch presentation click: A Novel Band-Steam Applicator

These types of herbicides are also called contact herbicides. PPO inhibitor means they slow down the production of the protoporphyrinogen oxidase (PPO) enzyme, which is used in chlorophill production. This inhibition also results in the formation of highly reactive molecules that attack and destroy lipids and protein membranes which ultimately affect cell membranes. This result in leaky cells and disintegration of the tissue.

Goal (Oxyfluorfen) is one of the earliest registered of these products (1980) but has only been used widely over the about the last 16 years. This is the only one of these that has problems with “lift off” or codistillation with water. ⁽¹⁾
According to University of CA IPM “In dry bulb onions, GoalTender may be tank-mixed with other pesticides such as bromoxynil, but tank mixes must only be used on older onions with well-developed cuticles to avoid unacceptable crop injury. Unacceptable injury may occur if applied to small onions without adequate cuticle development, and in conditions such as after cloudy or rainy weather. Follow the label closely to avoid crop injury when tank mixing.
Oxyfluorfen has some residual soil activity after application. It controls small broadleaf weeds, some grasses, and nightshade, and controls little mallow (cheeseweed) well ”. ⁽¹⁾

Other PPO herbicides are: Aim or Shark, Chateau, Sharpen or Treevix, ET, and Spartan. They work as contact herbicides and do not move through the plant.
Most of these products don’t have preemergence activity but when used at higher rates Goal and Chateau do.⁽²⁾ As the plant emerges from the soil and contacts the herbicide it dies, so it is recommended to avoid disturbing soil after the application of these products.
 
This week in Yuma oxyfluorfen uses:

1. Directed application in broccoli for goosefoot, lambsquarter, and cheeseweed control.
2. Broadcast application in onions for goosefoot, grasses and lambsqurter

 
References

1. https://cales.arizona.edu/crop/vegetables/advisories/more/weed173.html
2. https://ipm.ucanr.edu/agriculture/onion-and-garlic/integrated-weed-management/

VegIPM Update Vol. 17, Num. 11
May 27, 2026

Results of sticky trap catches below!!

Whitefly: Adult activity continues to increase across locations, yet these numbers do not reflect what we are seeing in the field on melon insecticide efficacy trials at YAC, numbers for untreated plots and melon virus incidence are well above what we have seen in other years. Historically whitefly numbers peak in July.

Thrips: Adult thrips activity remained steady across locations over the last two weeks. Historically, western flower thrips numbers peak in May.