Now that the weather has finally returned to normal for mid-October, the worm pressure we’ve been experiencing should begin to decline.  However, with many early-planted head lettuce crops beginning to rosette and folding-in to form heads, it would be wise to keep a keen eye out for corn earworm (CEW).  This fall could be important as pheromone trap catches spiked last week in several locations (see graph below) moths continue to be active.  Although pheromone trap counts don’t always correlate to field infestations, we have associated peak CEW moth trap counts with larval CEW activity in surrounding lettuce fields in the past.  Even with the cooler temps expected this next week, moth activity should be expected in fields and that means eggs being deposited in or on developing heads.

CEW can be very damaging in early fall head lettuce crops. On older plants beginning to form heads, larvae will migrate to the succulent terminal growth. If not controlled before the plant leaves fold in, they are protected from foliar sprays. By this time in plant growth, at-planting soil applications of Coragen or Verimark may not be effective enough to protect the heads. Once head formation begins, newly hatched larvae will usually bore into the head almost at once upon hatching.  Corn earworm is much more likely to bore into lettuce heads than other Lepidoptera larvae, rendering the heads unmarketable.  Larvae may enter the head from any point on the plants but can often be found burrowing in from the lower half of the head. 

If fields are not watched closely, infestations may not be noticed until the head is harvested. Once inside the head, it is virtually impossible to control the larvae with insecticides. 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 or cup over, you should treat as soon as possible.  Moreover, during mid-late October and early November it is probably a good idea to prophylactically apply a pyrethroid, methomyl or acephate in combination with larvicides (e.g., Radiant, Coragen, Proclaim) when heads begin to form.  The UA nominal threshold for CEW in head lettuce from the beginning of heading to harvest is1-2 larvae / 100 plants (1-2%).  Repeated insecticide treatments may be required to maintain low population levels if heavy pressure is sustained near harvest. Lab bioassays have shown that CEW larval mortality is most rapid when exposed to Lannate at 0.5 lbs (>90% mortality in 1 hour after exposure) and pyrethroids at high rates (>90% mortality in 3 hours), followed by Radiant,5 oz (>90% mortality in 12 hours).  By 24 hours, mortality was 100% for all the treatments including Coragen and Proclaim.  For more information on CEW management see Corn Earworm Management on Desert Produce.

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

Lettuce fields right now are covered with downy mildew after the unusual amount of rain we got this year in the desert southwest. 
Another disease to look out for is downy mildew in onions. 
Downy mildew of onions is caused by the fungus-like Stramenopile Peronospora destructor. The pathogen produces abundant sporangia that germinate directly acting as spores. Reported hosts other than onions include shallot, leek, garlic and chives. The fungus overwinters in volunteer hosts, cull piles, and debris. Spores are wind borne. Spores of the fungus present in soil or bulbs germinate, infect roots or bulbs, and develop systemically in the plant. Spores that land on the leaf surface produce local lesions that can spread systemically to younger tissue. Infection can spread rapidly under cool (34– 82 °F), damp conditions generating new inoculum within the field. The pathogen requires cool temperatures and the presence of free moisture (rainfall, dew or overhead irrigation) to infect onion plants. Under those conditions repeated disease cycles may occur with devastating results.
 
Disease management:  Regular scouting of field is important to assess disease severity and apply preventative fungicides. Disease management includes use of disease free bulbs, transplants and seed. Crop rotation with non host (small grain, corn) for at least 3 years. Destroy volunteer plants, debris and cull pile. Better soil drainage, better circulation, preventative spray can reduce disease occurrence. Always rotate fungicide from different groups to avoid resistance build up.

Pics : https://www.omafra.gov.on.ca/IPM/english/onions/diseases/downy_mildew.html
Sources: 
https://amarillo.tamu.edu/
https://barron.extension.wisc.edu/

A couple years ago, we conducted evaluations of various “new” technologies for cultivating weeds in cotton as compared to conventional methods. The new technologies included 1) a camera-guided side-shift hitch and 2) finger weeders, an in-row weeding tool (Fig. 1). Camera-guidance of the maneuverable hitch allows cultivating tools to be positioned close to the seed row. In the study, the uncultivated band was 3.5" for the camera-guided system, and 6” for the conventional cultivator.  The aim of evaluating these technologies was to determine their efficacy in controlling herbicide resistant weeds. Trials conducted 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. Overall weed control using the two technologies together was roughly > 90% for broadleaf weeds and about 85% for all weeds species.
Studies conducted by Texas A&M over two years showed similar results (Dotray et. al, 2021).

It is logical to think that similar type results would be realized in vegetable crops such as broccoli and cauliflower, plants that also have fairly long plant stems at the seedling stage of growth. A better than 40% reduction of in-row weeds would significantly lower hand weeding requirements. If you are interested in trying these technologies in vegetable or other crops on your farm, please contact me. We still have the equipment and I’d be happy to work with you.

A presentation given on the trial results and videos of the equipment used operating can be found by clicking here or on image below.

References
Dotray, P.A., Keeling, J.W., & Russell, K.R. 2021. Precision cultivation with finger weeder systems. Project No. 20-190 Final Report. Cary, N.C: Cotton Inc.

Acknowledgements
Project partially funded and supported by Arizona Cotton Growers Association, Cotton Inc., KULT-Kress, LLC and Keithly-Williams Fabrication. We thank them for their support.

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

Fig. 2. Click on image above to watch presentation on precision cultivation and
in-row weeding technologies.

 

 

The following is the FIRST WEED SCIENCE ARTICLE OF THIS NEWSLETTER published January 13, 2010 by our friend Barry Tickes.

The selective grass herbicides are good rescue type treatments in vegetables for grasses that have gotten through Pefar, Kerb and Balan. These include Poast (sethoxydim), Select (clethodim) and Fusilade (fluazifop) and the generics of these products. These herbicides are all slow and even slower as temperature and day length drop. If you don't like weeds, you can have the satisfaction of watching them suffer for a long time. Treated grasses should stop growing immediately and will slowly turn yellow, red and gradually disappear as the crop grows. This will likely take 2 to 3 weeks. Poast is the slowest and Select is the fastest. All of these herbicides require the addition of a crop oil concentrate except for Select Max which you can use with either a crop oil concentrate or non-ionic surfactant. Some reports indicate that ammonium sulfate will help in cold weather. If you have used one of these products and don't see adequate control within 3 or 4 weeks, please contact us and we'll look at it with you.

As Barry promised in his 2010 article he will be looking at some field trials with me today!

Area wide Insect Trapping Network   VegIPM Update, Vol. 14, No. 24, Nov 1, 2023            
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth captures have steadily decreased over the past 2 weeks, and areawide about average for late-October.
 
Beet armyworm:         
Trap counts reached their highest levels so far this season, particularly in Tacna, Wellton and Yuma Valley, and about average for late October.
 
Cabbage looper:           
Cabbage looper numbers decreased areawide, and are still below average for this time of the year.
 
Diamondback moth:   
Sporadic DBM activity in low numbers throughout the area, trending well below average for late October.
 
Whitefly:                     
Adult movement increased in the past 2 weeks and above average for late October.
 
Thrips:                           
Thrips adult activity peaked in the last two weeks, and trending below average in October.
 
Aphids:                        
Winged adults continue to be captured for the season, consistent with heavy winds from W-NW. Aphid captures thus far have been well below average. 
 
Leafminers:                  
Adult activity decreased in most areas, and trending about average for late October.