It has been consistently recognized for several decades that over 90% of the leafy green vegetables consumed in the United States (US) and Canada from November through March each year are grown in the lower Colorado River Valleys, primary in the Yuma area valleys and the Imperial Valley (Renick, 2013 and Satran, 2017).  
 
In some recent articles published in the Agronomy Journal, Dr. Ashley McCarthy and her colleagues at the University of Vermont have evaluated the differences between nutritional recommendations in the US versus actual consumption.  They also studied vegetable crop production capacities in the US and total cropland requirements to meet vegetable crop production needs if everyone in the US consumed the recommended amounts of vegetables for good nutrition (McCarthy et al., 2022 and McCarthy et al., 2023).
 
In this project, McCarthy and her colleagues conducted a set of “thought” experiments.  To address their first question regarding our current capacity in the US to support Americans with diets complete with the daily recommended fruits and vegetables, they found that current domestic production would only provide 29% of the fruit and 53% of vegetable crops to meet that need.
 
They next examined climate, soils, topography, and other biophysical aspects of the land in the US.  From this they determined that the US has an abundance of land suitable for fruit and vegetable crop production, more than 741K acres (300M ha) among the contiguous U.S. states.  However, they do point out that less than half of the land they identified is currently used for crop production.  
 
They determined that of all the land in the US that could potentially go into fruit and vegetable crop production, 47% is currently in agriculture and 53% is not.  Many agronomists and soil scientists in the US would offer significant doubt about the realistic possibility of having that much land available for crop production, not to mention the difficulty of converting that land into agricultural production. 
 
The next question in their series of thought experiments was to evaluate the capacity in the U.S. to produce sufficient fruits and vegetables to make the nation self-reliant and not depend on imported fruits and vegetables.  From their analysis, McCarthy and her colleagues determined that U.S. could indeed become self-sustaining for fruit and vegetable crop production, even if all Americans consumed the daily recommended amounts of fruits and vegetables.
 
The results from the work of McCarthy and her colleagues are interesting but they are not without some significant points of concern or weaknesses in their argument.  For example, they recognize that to realize the projected capacities for fruit and vegetable crop production in the U.S. would require more than a doubling of the current land currently devoted to these crops.  Currently, approximately 11.6M acres (4.7M ha), or 3% of the U.S. cropland is devoted to fruit and vegetable crops.  To meet the objectives of these experiments, the U.S. would have to increase cropland devoted to fruit and vegetable production to 30M acres (12.2M ha).  
 
I am rather dubious of the capacity to convert nearly 20M acres (8M ha) from current crop production systems to a fruit or vegetable crop production system in the U.S.   As we know in the fruit and vegetable production systems in the southwest U.S., there is a tremendous amount specialized equipment, infrastructure, and expertise required to develop and manage systems of this type.  In addition, the labor requirements for fruit and vegetable crops are much larger than the large acreage commodity crops that are being grown on most of the farmland in the U.S.
 
Of the numerous questions that arise from a review of the experiments and conclusions of McCarthy and her colleagues, one major point that they do also recognize is the lack of consideration of water resources necessary to support this level of fruit and vegetable production in the US.  That point is a major limitation and it is exacerbated by the changing climate that we are experiencing throughout the western U.S.
 
There are some good points that come from studies like these.  For example, should self-reliance for food production be a strategic goal in the US?  Currently, the US imports a lot of food products, including many fruits and vegetables (non-leafy green vegetables).  Domestic production provides over 90% of the leafy green vegetables consumed in the US and Canada from November through March each year are grown in the lower Colorado River Valleys, primary in the Yuma area valleys and the Imperial Valley.  This production is totally dependent on irrigation water from the Colorado River.
 
If that last question is answered affirmatively, this would have a huge impact on preserving farmlands and shifting from urban to agricultural land development.
 
This also brings up the consideration of regional food production systems in the US.  For example, Arizona and certainly the southwestern region of the US could be self-reliant for food production if necessary.  Considering the diverse mix of crops and animals grown and produced for food systems in Arizona and the region currently, this is quite feasible for crop production systems in the Southwest.  Of course, the major limiting factor in providing this level of self-reliance in the desert Southwest is water.
 
These thought experiments have value, despite the practical flaws that can be identified.  Very importantly, they are constructive in helping us recognize the tremendous present and future value of the fruit and vegetable crop production systems in the desert Southwest we currently have today.  
 
Maintaining agricultural water allocations is important to support the production systems currently in place.  It is also important to consider the food and nutritional needs of Americans today and in the future and how and where those crops will be grown to support these needs.
 
Considerations for Colorado River water allocations to agriculture for the future are extremely important.  This is true not only to protect and support the systems currently in operation, but it is also an important aspect of food security for the US in the future.
 
 
 
References:
McCarthy, A. C., Griffin, T. S., Srinivasan, S., & Peters, C. J. (2023).  Capacity for national and regional self-reliance in fruit and vegetable production in the United States. Agronomy Journal, 115, 647– 657. https://doi.org/10.1002/agj2.21305
 
McCarthy, A. C., Srinivasan, S., Griffin, T., & Peters, C. J. (2022). A geospatial
approach to identifying biophysically suitable areas for fruit and vegetable
production in the United States. Agronomy Journal, 114, 2845–2859. 
https://doi.org/10.1002/agj2.21138
 
Renick, O. 2013.  Freezing California Lettuce Boosts Salad Costs: Chart of the Day
Bloomberg, 3 February 2013.
 
Satran, J.  2017.  This Is Where America Gets Almost All Its Winter Lettuce Who knew?  Huffingtion Post. https://www.huffpost.com/entry/yuma-lettuce_n_6796398

I am seeking samples of downy mildew on lettuce from around Yuma County to support the Michelmore Lab and their ongoing efforts to help characterize the downy mildew populations of the United States. The Michelmore Lab has led the charge on a survey of Bremia variants since 1980 and has been instrumental in demystifying the gene-for-gene nature of lettuce resistance to downy mildew.

Their group invites growers across the United States to submit downy mildew infected plant samples, which are then used to culture the Bremia on live host plants. The team then inoculates a panel of lettuce varieties carrying known resistance genes to determine the race of each isolate they receive. Identifying which races occur in which specific fields is essential to guiding the breeding of new resistant cultivars and maximizing the effectiveness of host-based genetic disease management. The data obtained from these tests are also used to designate new Bremia races through the International Bremia Evaluation Board.

Your contribution will help breed better lettuce for Yuma. This means less breakdown of resistance in the field, and better yields for Yuma growers. To facilitate these submissions the Yuma Plant Health Clinic will be setting up a separate drop-off point and submission sheet for downy mildew sample submissions in the same hallway we use for standard plant diagnostic submissions. The drop-off point will be clearly labelled and consist of a chest-style refrigerator and printed copies of the submission form. It is vital to keep these samples cool so they remain viable for future inoculations, so please place your samples inside of the refrigerator before you leave.

Shipping will be handled by the clinic. All we ask is that you fill out the submission form as completely as you can. An example of the questions that are asked in that form so you can prepare ahead of time can be found HERE . 

Over the last couple of years, we developed a prototype steam applicator for injecting steam into the soil prior to planting. The concept behind soil steaming is similar to soil solarization - heat the soil to levels sufficient to kill soilborne pathogens and weed seeds (typically 140 °F > 20 minutes). The device is principally comprised of a 63 BHP steam generator mounted on an elongated bed shaper (Fig. 1). 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.

Trial results have been very promising and reported in previous UA Veg IPM articles. In brief, the multi-year studies have shown that soil steaming provides excellent weed control (>90%), suppresses problematic soilborne diseases (Fusarium wilt of lettuce> 50%, lettuce drop > 70%) and increases crop yields (>24%).

This season, we would like to demonstrate the technique to interested growers. In addition to obtaining grower feedback on the viability of soil steaming, a second objective would be to validate our small plot research results at the field scale level. The machine can be adjusted to work with most bed configurations including 40”, 42”, 80” and 84” beds, and work with any crop, including organic crops (soil steaming is organically compliant). So far, the device has been successfully tested in iceberg lettuce, romaine, baby leaf spinach and carrot crops.
If you are interested in an on-farm demo of soil steaming, please let me know. I’d be happy to work with you.

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. Click here or on the image above to see the device in action.

 

 

Image by: Jim Daily

Hare Barley, Mediterranean, or Wild Barley (Hordeum murinum) has been increasing at the Yuma AZ Valley and the Mesa. This week we have received some samples for ID from our friend PCAs.
It’s a cool season annual grass native to Europe with dense stiff awned spikes. Early in the season before the flower spikes develop, they can be a very good forage but when the spikes emerge can injure the mouths, eyes, nasal passages, ears, and skin of animals.
It is found throughout California up to 3300 feet (1000 m) and inhabits agricultural land, disturbed sites, and unmanaged natural areas³. The seedheads are unbranched, awned, stems and leaves are hairless, and the ligules are membranous. The collar region and auricles can be seen in the image below from the University of CA³.
The Hordeum murinum complex is the most widespread of all the other Hordeum species, and the origin of its distribution of was Central Europe, the Mediterranean area, North Africa, and Western Asia¹.

Collar region of (left to right) hare (wild) barley, wheat, and wild oat.
Photo by Jack Kelly Clark³.

References:

1.   Retrieved from: https://en.wikipedia.org/wiki/Hordeum_murinum
2. https://weeds.nmsu.edu/factsheet.php?weed_id=101
3. https://ipm.ucanr.edu/PMG/WEEDS/hare_barley.html

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 3, Feb 7, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
CEW moth counts increased in the Rol and Dome Vallley areas, above average for this time of year. 
 
Beet armyworm:         
Trap counts low; lower than average compared to previous years.
 
Cabbage looper:           
Cabbage looper counts increased in most traps and about average for this time of season.
 
Diamondback moth:       
DBM moths counts increased in most areas. About average for this time of the year.
 
Whitefly:                       
Adult movement negligible, typical for mid-winter. 
 
Thrips:                          
Thrips adult counts remain low, likely in response to rainfall in late December. Currently, numbers are below average compared with previous years.
 
Aphids:                        
Aphid movement increased significantly in the past two weeks, particularly in North Yuma and Gila Valleys. Highest numbers we’ve seen in 11 years.
 
Leafminers:                   
Adults remain low in most locations, average for January.