With local temperatures expected to increase in the next few weeks, insect activity should also start to pick up. Even though worm pressure has been light in the field for the past month or so, it would be wise to keep a look out for corn earworm (CEW).  In the past, unusually high CEW abundance has occurred on late head lettuce, particularly in the Dome/Wellton areas.  Our latest trap catches indicate that moth counts have been nearly bottomed out for some time.  However, we did see a slight increase in CEW trap captures in the Dome and Yuma Valleys last week (~ 0.5 moths/trap/night).  This is typical for February (Areawide Trap Network) and could be the calm before the storm. In the spring seasons where larvae were heavy (2014-2016), trap catches started to increase in late February-early March and peaked by mid-to-late March. These increased trap numbers should be used as an early indicator that moths are actively flying at night at higher abundance and PCAs should start to scout more aggressively for eggs and larvae.  CEW can be very damaging in spring crops once head formation begins; larvae will usually bore into the head 1-2 days upon hatching.  Corn earworm is much more likely to bore into lettuce heads than other Lepidoptera larvae, rendering the heads unmarketable.  If fields are not watched closely, infestations may not be noticed until the head is harvested. Once inside the head, control of larvae with currently available insecticides is not possible. Thus, pay careful attention for newly oviposited eggs (laid singly) on lettuce plants. If you are beginning to find eggs and suspect that CEW are active in the field when plants are beginning to head, it would be a good idea to treat at regular spray intervals (~ 7days). The UA nominal threshold for CEW in head lettuce from early heading to harvest is 1-2 larvae / 100 plants. Essentially, you find one you spray.  Repeated insecticide treatments may be required to maintain low population levels near harvest.  Most contact insecticides recommended for Lep larvae are active against CEW. Furthermore, the addition of a pyrethroid with thrips, aphid and/or fungicide sprays may be cheap insurance against larvae infesting heads as you approach harvest. For more information on CEW management and control recommendations see Corn Earworm Management on Desert Produce and the 2022 Lep Control Chart.

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.

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum,  is one of the oldest described Fusarium wilt diseases and the most economically important disease of watermelon worldwide. It occurs on every continent except Antarctica and new races of the pathogen continue to impact production in many areas around the world. Long-term survival of the pathogen in the soil and the evolution of new races make management of Fusarium wilt difficult. 
In 2022, we had  a lot of watermelon fields infected with Fusarium from Winterhaven to Yuma, Wellton, and Mohawk Valley. Rain, and overwatering of fields when plants set fruits might have contributed to the disease development. It is always a good idea to look out for any potential diseases that might occur this year! 
 
Symptoms of Fusarium can sometimes be confused with water deficiency, even though there is plenty of water in the field. In Yuma valley we have seen fusarium problem in some overwatered fields. 
Initial symptoms often include a dull, gray green appearance of leaves that precedes a loss of turgor pressure and wilting.  Wilting is followed by a yellowing of the leaves and finally necrosis.  The wilting generally starts with the older leaves and progresses to the younger foliage. Under conditions of high inoculum density or a very susceptible host, the entire plant may wilt and die within a short time.  Affected plants that do not die are often stunted and have considerably reduced yields.  Under high inoculum pressure, seedlings may damp off as they emerge from the soil. 
 
 Initial infection of seedlings usually occurs from chlamydospores (resting structure)  that have overwintered in the soil.  Chlamydospores germinate and produce infection hyphae that penetrate the root cortex, often where the lateral roots emerge.  Infection may be enhanced by wounds or damage to the roots.  The fungus colonizes the root cortex and soon invades the xylem tissue, where it produces more mycelia and microconidia.  Consequently, the fungus becomes systemic and often can be isolated from tissue well away from the roots. The vascular damage we see in the roots is the defense mechanism of the plant to impede the movement of pathogen. 
 
Disease management include planting clean seeds/transplants, use of resistant cultivars, crop rotation, soil fumigation, soil solarization, grafting, biological control. An integrated approach utilizing two or more methods is required for successful disease management.

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:

Family	Common Name	Trade Name
phenoxy	2,4-D	Pasture pro, others
	2,4-DB	Butyrac Butoxone Rhomene
	MCPA	Rhonox Chiptox Battleship
	MCPP MCPB	Several names Several names
benzoic acid	dicamba	Banvel Clarity
carboxylic acid	Picloram	Tordon 22K
	Clopyralid	Stinger Reclaim
	triclopyr	Remedy Grandstand
	quinclorac	Facet

 

 

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased considerably y in the past 2 weeks and about average for late summer
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Dome Valley and Wellton) particularly near alfalfa
 
Cabbage looper:         
Cabbage looper numbers remain low consistent previous years.
 
Diamondback moth:      
DBM moths were not caught in any trap since June; average for this time of the year.
 
Whitefly:                      
Adult movement decreased in past 2 weeks consistent with previous years
 
Thrips:                         
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity has highest in Wellton and Dome Valley, and slightly above average for early August