Western flower thrips numbers are building and will likely continue as temperatures are ideal for thrips movement and development. It is important to minimize thrips development not only to prevent cosmetic damage to lettuce, but to minimize the spread of INSV.   As expected, INSV infected plants have been found again in desert lettuce. We confirmed out first case for the 2023 fall season two weeks ago in organic romaine transplants in Tacna. This is almost the same time as the last 2 years (INSV was first confirmed in 2021 and 2022 in mid-Oct). Additionally, this week we confirmed the presence of INSV in another organic romaine field found a few miles away.  Not surprising since the plants originated from Salinas where INSV outbreaks have been occurring the past 3 years.  This past season, INSV was comparatively light in Salinas and we’re hoping that this translates to less virus coming into the desert on transplants.  So far, we’ve yet to find any INSV infected plants in adjacent direct seeded lettuce. If experience tells us anything though, we can expect to find INSV in surrounding lettuce fields as the season progresses. However, to prevent or minimize further spread to adjacent fields, thorough management of thrips in infected lettuce is advised.
Historically, management of thrips was targeted at preventing damage caused by thrips feeding to marketable lettuce leaves. However, that changed with the discovery of INSV in desert lettuce.  It’s important to understand how thrips infect lettuce plants with INSV.   INSV infects lettuce two ways.  The first is Primary infection where INSV infected thrips adults move into a lettuce field and begin feeding, simultaneously transmitting INSV to otherwise healthy plants. In theory, the greater the number of infected thrips moving into the field, the higher the incidence of primary infection. Secondary infection or spread occurs when populations colonize and thrips larvae acquire INSV by feeding on an infected plant, complete development and emerge as infected adults, capable of transmitting INSV throughout the field or nearby lettuce fields/weeds. Keep in mind, adults only transmit INSV, whereas only larvae acquire the virus from an infected plant. To minimize the areawide spread of INSV this fall and into next spring, PCAs should consider the following recommendations:

1. Early and aggressive spray timing in High-risk areas.  It is advisable that PCAs preventatively treat lettuce fields early and aggressively in the following high-risk scenarios:

• Lettuce originating from Salinas should be treated before or shortly after transplanting.
• Direct-seeded lettuce fields grown next to, or near, lettuce fields where transplants originated from Salinas should be treated early and aggressively.

2. Focus on minimizing Secondary spread.   Because adults can be difficult to control, prevent larvae from completing development to the adult stage and moving throughout the field. It’s hard to prevent primary infection from the outside but minimizing larvae populations should help suppress the secondary spread of INSV if it is present in the field.

3. Using Insecticides Differently. Consider incorporating the following approaches in your IPM programs:

• Adding Lannate or Torac with chemical thinners/smart sprays.
• Rotating Minecto Pro or Exirel with Radiant for Lep and/or whitefly control in fall lettuce
• Rotating Beleaf or Acephate with Movento when aphid control is needed.  
• All these products have shown to provide control or suppression of western flower thrips larvae.

4. Test symptomatic plants at once.   The earlier you confirm INSV in a field the better chance you have of reducing secondary spread within the field and, perhaps as important, to surrounding lettuce in the area.  Immunostrip test kits are available, and the UA Diagnostic Plant Pathology Diagnostic Lab can confidentially confirm the presence of INSV on symptomatic plants.

 
For more information, please go to this link: Thrips and INSV Management in Desert Lettuce

Among the many challenges facing the agricultural community, communication is among the most important.  Recent water shortages have raised the attention of the public to agriculture and specifically crop production systems in the desert Southwest.  This has revealed an enormous lack of knowledge on the part of the non-agricultural public about the process of crop production and the management required to produce crops successfully and sustainably in the desert.  As it is commonly stated: “Facts may be facts, but perception becomes reality.”
 
Dwight D. Eisenhower once said, “Farming looks mighty easy when your plow is a pencil and you’re a thousand miles from the cornfield.”  We have certainly seen these tendencies in action during the past few years with an abundance of well-intended advice and directions from the non-ag public regarding how farmers and agricultural entities should deal with the water shortage.
 
Part of our challenge in working with people from non-ag or urban sectors is communicating some basic facts and the truth about agriculture.  This challenge is compounded by the abundance of misinformation, the tendency for people to consider these issues emotionally as opposed to rationally, and the associated lack of interest many people have in hearing about statistics and science-based information.  So, the challenge in communication is often centered on some basic foundational points and trying to make it relevant to people.
 
Most of the time in communicating agricultural perspectives to urban or non-ag audiences we are working with people who are several generations removed from agriculture.  In 1900, nearly 40% of the U.S. population worked on farms and ranches and 60% lived in rural areas.  Today, those numbers are only 1% and 20% (Figure 1).  Considering that, it is easy to understand the disconnect we commonly experience between agricultural realities and common perceptions in the urban sectors.
 
Even with less people working in agriculture, crop yields have continued to increase (Figure 2).  For example, contrasting crop yields in U.S. from 1900 to 2014 shows that corn yields in 1900 were only 18 % of what they were in 2014.  Similarly, 1900 wheat yields were only about 30 percent of what they were in 2014.  This has been largely due to the adoption of improved mechanization, synthetic fertilizers, improved genetics, and seed quality.  Also, crop yields have been better protected with integrated pest management systems for the management of insects, weeds, and diseases.  Major increases in crop yields have been particularly realized since World War II.  The irony is that all these factors contributing to higher yields are commonly the points of fierce criticism from the non-ag populace.
 
Simple things like the significance of photosynthesis and the capture of light energy from the sun with water from the soil and carbon dioxide (CO₂) from the air and then converted into the plant dry matter that humans and other animals consume and depend on for survival is a connection not made by most people.  The process of photosynthesis and how we manage it is really a fundamental piece of our agricultural foundations.  It also describes the basic relationship of water to crop production.  We cannot assume that people understand even these basic facts.
 
In production agriculture we are dependent on natural resources, such as water, climate, and the soils of this region.  In the desert Southwest, our capacities to produce the highest crop yields of anywhere on the planet with premium quality products is largely a function of the dry climate, our capacity to provide sufficient water by irrigation, and the utilization of the tremendous resources of geologically young and highly fertile soils.
 
Another critical resource that is essential to the crop production systems of the desert Southwest is the skill and expertise provided by the people who are farming and managing these systems.  In my work with the University of Arizona over the past 36 years, I have had the opportunity to work with people in crop production regions in many parts of the world, commonly in arid and semi-arid regions.  I am always impressed with the skill, commitment, and capacity of farmers all over the world.  But the skill levels required to survive and compete in crop production systems in the desert Southwest are unsurpassed. 
 
Farmers and the full array of personnel including technicians, pest control advisors, agronomists, irrigators, farm operators, business managers, mechanics, etc. are essential in the production of crops.  Successful crop management requires the successful integration of all these components and much more.  Improvements in our systems of crop production include our constant efforts to improve efficiency in the integration of these essential components.
 
Crop production efficiency comes in at least three different forms: economic, agronomic, and environmental.  These three aspects of crop production efficiency are all important and they can be met simultaneously, but economic survival is essential, and it becomes first and foremost in the management of a farming operation.  If a farm is not profitable it does not survive.
 
A tremendous amount of technical knowledge and skill is required in crop production and an effective understanding and application of scientific knowledge is essential.  Beyond the scientific capabilities required, there is also a high degree of skill required to manage and effectively integrate everything into a crop production operation.  Thus, it is a fact that crop production is a combination of art and science.
 
Effectively communicating agriculture and basic facts about food production is a real challenge for those of us working in agriculture.  As we have seen recently with the challenges that we have faced with the water shortages, the survival of agriculture crop production systems in the desert Southwest will be dependent at least in part upon our capacity to effectively communicate to the non-ag or urban sectors of our state, region, and nation.
 
The manner of this communication is one of our grand challenges for current and future sustainability of agriculture in the desert Southwest.  I find this to be a challenge within the university community and even within a college of agriculture.  It is not always easy but it is important for all of us in the agricultural community to understand and engage in this effort to communicate appropriately with our fellow citizens in non-ag and urban sectors when given the opportunity.  We have a lot at stake and we are all in this together.
 
A broad separation between public perception and reality exists and it is important to understand that.  Perhaps these water shortage situations can serve as a platform for improving public knowledge of agriculture and crop production.

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%). Lettuce ‘Magosa’ was seeded, then sprinkler-irrigated to germinate seed on Nov 2, 2021 on double rows 12 in. apart on beds with 42 in. between bed centers.  All other water was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed, which contained two 25 ft rows of lettuce. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.

 
Powdery mildew (caused by Golovinomyces cichoracearum) efficacy trial treatments were made on January 13^th, January 25^th, and February 1^st 2022. Disease was first seen on 1-20-2022. Disease rating was done on March 9, 2022.   Disease severity was determined  by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 0.5 = one to a few very small powdery mildew colonies on bottom leaves; 1 = powdery mildew present on bottom leaves of plant; 2 = powdery mildew present on bottom leaves and lower wrapper leaves; 3 = powdery mildew present on bottom leaves and all wrapper leaves; 4 = powdery mildew present on bottom leaves, wrapper leaves, and cap leaf; 5 = powdery mildew present on entire plant. These ratings were transformed to percentage of leaves infected values before being statistically analyzed. Yield loss due to rejected lettuce heads would likely begin to occur on plants with a powdery mildew rating above 2.0 (percentage of leaves infected value of 40).         

The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. All treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. The most effective fungicides were Luna sensation and Luna Experience for  this trial.

Last month, we investigated the use of applying steam to the soil to control weeds in baby leaf spinach. In the study, we utilized the prototype steam applicator described in previous UA Veg IPM articles to inject steam into the soil prior to planting. The concept is to heat the soil to levels sufficient to kill soilborne pathogens and weed seeds (140 °F > 20 minutes). The device is principally comprised of a 63 BHP steam generator mounted on an elongated bed shaper (Fig. 1a). The apparatus applies steam via shank injection and from rectangular ports on top of the bed shaper. After cooling (< ½ a day), the crop is planted into the disinfested soil. 

In the trial, the unit’s bed shaper (84” wide) was outfitted with twenty-four steam injection shanks positioned to inject steam into the soil at a depth of about 2” (Fig. 1b,1c). Six injectors were in a rank towards the front of the bed shaper with each injector spaced about 10.4” apart. Three additional ranks of 6 injectors, also with 10.4” injector spacing, were positioned behind the first rank. Ranks of injectors were offset such that the spacing between injectors across the frontal cross-section of the bed shaper was 2.6”. Travel speed was 0.20 mph.

Results showed that steam treatment provided very good control of broadleaf weeds (89%) and moderate control of grassy weeds (65%) (Table 1, Fig. 3). Combined, overall weed control was 80%. The predominant species at the site were nettleleaf goosefoot, thumble pigweed, ground cherry, common purslane and junglerice. Although weed densities were still high in the steam treated plots (1.8 weeds/ft²), hand weeding times were reduced by a factor of 5 as compared to the untreated control.

Work rates and fuel costs were considered marginally acceptable at 0.14 ac/hr and $597/ac, respectively. However, it is estimated that travel speed can be increased by 50% by operating the device when initial soil temperatures are high (>130 °F) as compared to this study where soil temperatures were moderate (110 °F) since much less heat energy is needed to raise soil temperatures to target levels. If a 50% increase in travel speed were realized, work rate would be improved to 0.20 ac/hr (5 hr/ac) and fuel costs would be about $400/ac. These values are very reasonable and show good potential for use of the technique in spinach or spring mix crops where costs for hand weeding are very high. Later this summer, we plan to conduct trials in high temperature soils to determine the maximum travel speeds that can be utilized for effective weed control using steam.
If you are interested in soil steaming and would like a demo or to evaluate the machine on your farm, please let me know. I would be happy to collaborate with you.

Acknowledgements
This work is supported by the Arizona Specialty Crop Block Grant Program and the Crop Production and Pest Management grant no. 2021-70006-35761 /project accession no. 1027435 from USDA-NIFA. We appreciate their support. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

Fig. 1. a) Band-steam applicator principally comprising a 63 BHP steam generator
mounted on a bed-shaper applicator sled. Steam applicator sled b) top view and
c) bottom view.

Table 1. Weed density and control of weeds with soil applied steam in baby leaf spinach trial.

Fig. 3. Weed control with steam in spinach. Steam was applied to the soil at a 2”
depth via shank injection prior to planting (a) and untreated control (b).

It is reported that the herbicidal activities of Plant Growth Regulators (PGRs) were discovered in the 1940’s.  Then, investigators in England and in the United States started their research on this type of herbicides¹.

Some of these substances are hormones produced naturally by the plants and other are synthetically produced. Examples of naturally occurring growth regulators are gibberellins, auxin, cytokinin. Some stimulate stem elongation and cell elongation. One of the first synthetic selective herbicides developed is 2, 4-D (2,4-dichlorophenoxiacetic acid).
PGRs are used extensively for broadleaf weed control in grass crops in this region such as grain production, bermudagrass, alfalfa, cole crops, sugarbeet, forages, and turf grasses. These herbicides upset the natural balance of the hormones that controls cell division, cell enlargement, protein synthesis, and respiration. That is why this group of herbicides is sometimes called the “hormone herbicides”². In our area growers are very careful using these products due to volatility with our summer temperatures and the problems caused to sensitive crops.

According to a report from Texas A&M “phenoxy growth regulator herbicides are reported to have the least plant activity and soil residual activity; the carboxylic acids generally have the most. Broadleaf crops and turf grasses should not be planted into soils recently treated with these herbicides because they severely inhibit seedling emergence”².
 
Some PGRs:

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 21, Oct 16, 2024

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

Corn earworm: CEW moth counts increased in most traps; about average for early October.

Beet armyworm: Trap counts increased in most areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts still most locations, below average for this time of the season.

Diamondback moth: Adult activity increasing, particularly in the Yuma and Dome Valleys.  Above average for this time of season.

Whitefly: Adult movement increasing Tacna, Dome Valley and Yuma Valley; overall about average for early October.

Thrips: Thrips adult movement picking up in all areas, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; about average for early October.