Now that the days are getting longer and temperatures remain unseasonably warm, aphids are likely to become more abundant.  Experience has also shown that aphid population growth begins to increase significantly once the weather warms in January.  Our local weather forecast for the next two weeks suggests that temperatures will be in the low 70’s with moderate nighttime lows in the mid-40’s. These conditions may be ideal for aphid population growth, which is optimal at average temperatures of 55-60 °F. However, the lack of rainfall this fall and winter so far may play to your advantage. 

Previous research has shown us that aphids tend to be more abundant during warm, wet winters. Nonetheless, we’ve seen an unusual abundance of aphids earlier this fall and that could continue. So, keep an eye out for colonization.

Aphid flights are ahead of schedule compared to the past few seasons (see graph below). Trap captures of winged aphids peaked in Nov and continued to move in above average numbers in December. They have been particularly heavy in the North Gila and Yuma Valleys.  There were several reports of green peach aphid colonizing lettuce and broccoli in both conventional and organic produce last month, and at the Yuma Ag center, green peach aphids are beginning to colonize small plants, and we should be starting efficacy trials soon. Be on the lookout for lettuce and foxglove aphids too (see Aphid ID Guide) as they tend to develop faster at higher temperatures than other aphid species found in the desert. Consequently, PCAs should be extra vigilant in scouting for aphid colonies.  If a field has been treated with imidacloprid at planting, then chances are you are in pretty good shape on young produce. However, imidacloprid doesn’t last all season.  Regardless of whether you find green peach, or lettuce aphid the key to effective aphid management with foliar insecticide is to initiate sprays at the time apterous (wingless) aphids begin to colonize.  The action threshold is when you can find aphid colonizes on > 5% of plants sampled.  Of course, this requires diligent scouting and sampling.   On older lettuce, make sure you thoroughly examine developing heads/hearts. Fortunately, PCAs have many alternatives for aphid control (see Aphid Management on Desert Produce_2025).  So, keep your eyes open for new aphid colonies and treat early to keep ahead of the populations.  

For more information on aphid management visit these publications: 

• Keys to Aphid Management in Leafy Vegetables
• Aphid Management on Desert Produce_2025
• Aphid ID Guide

Rapidly changing conditions are a common feature in the agricultural arena.  Things are in a constant state of flux in terms of climate, economics, methods of operation, etc.  However, in the past few years, principally during the pandemic and post-pandemic times, changing conditions in agriculture for the desert Southwest have been extremely rapid and substantial.
 
Supply chain issues have been disruptive to many sectors of the economy and that has certainly affected agricultural operations.  Things that have commonly been standard or easy things to manage in the past such as the simple need of replacing equipment or parts have become complicated and expensive.  
 
We have become aware of fragile supply chains and the exposure of single points of failure that can have huge domino effects in many facets of our society, including agricultural industries.  For example, during the pandemic it cost nearly $40,000 to move a shipping container from Asia to the U.S. and now things are starting to catch up and it has been reported that containers can now be shipped from Asia to the U.S. for less than $3,000.00.  
 
Fertilizer prices for many materials have more than doubled in recent years, primarily due to basic supply and demand pressures.  Fertilizer supplies have been subject basic economic pressures and further exacerbated by the war in Ukraine and the associated changes in natural gas supplies.  
 
Fertilizer Supply and Cost
In a recent report from DTN market analysis (Formerly: Telvent DTN, Data Transmission Network) for the second week of November, retail U.S. fertilizer prices were not substantially different than in October but did have some slight variations with five fertilizers showing marginally lower prices than in October and three other key fertilizers tracking slightly higher.  It is important to note that DTN designates a “significant” difference in prices with a move of 5% or more.
 
The five fertilizers that were marginally lower in price included monoammonium phosphate (MAP), potash, urea, 10-34-0, and anhydrous ammonia.  Di-ammonium phosphate (DAP), urea ammonium nitrate (UAN)-28, and UAN-32 were slightly higher in price in mid-November, Table 1.  Costs per pound of nitrogen (N) is shown for primary N sources in Table 2.

MAP	Potash	Urea	10-34-0	Anhydrous	DAP	UAN-28	UAN-32
$978	$848	$812	$753	$1,415	$930	$584	$681

Table 1.  Mid-November retail prices in U.S. markets for several fertilizers.  Source: DTN
 

Anhydrous Ammonia	UAN-28	UAN-32
$0.88	$1.04	$1.06

Table 2.  Comparative prices per pound of N.  Source: DTN
 
Crop commodity prices have been higher recently, sometimes to the extreme.  However, the increasing costs of crop production have generally overrun the increasing returns on a strong market.  In a recent report on western crop production conditions, estimates of cost of production increases in the past year are 135% higher than in 2020 while the return values to farmers have been about 127% higher.  Thus, a nearly 10% negative differential exists which exerts a strong impact on the crop production systems of the desert Southwest.
 
The American consumer is seeing this as well.  In the American Farm Bureau Federation’s 37th annual cost survey from volunteer shoppers for Thanksgiving dinner has shown that prices are up 20% this year.  This increase is in addition to the 14% increase experienced in 2021.
 
Nutrient Management
Developing a conservative approach to nutrient management is often considered a risky venture in crop production systems, particularly with a short season crop like a leafy green vegetable that has a premium on quality as well as yield.  However, under high fertilizer price conditions and/or tight supply, there is a greater incentive to develop and employ a more conservative approach to nutrient management.
 
To maximize nutrient management efficiency, the 4R concept of plant nutrient management and application can be helpful.  The 4R concept consists of applying:
 
 1.   Right fertilizer source at the
 2.   Right rate, at the
 3.   Right time and in the
 4.   Right place
 
Along with the 4R nutrient management approach, assessing plant-available forms of the nutrients present in the soil by evaluating soil tests with appropriate indices is a good step in the develop of a more efficient nutrient management program.  Then splitting nutrient applications, particularly mobile nutrients such as N in line with crop uptake and utilization are good steps towards higher fertilizer use efficiency by the crop.  Thus, timing, methods, and rates of nutrient applications are critical (e.g, 4R management).
 
In agriculture we know quite well that we have no control over markets and the costs of crop production inputs.  However, we can control these inputs in the field, and we do have some tools at our disposal that can be helpful in the process.

With the start of 2022 growing season we are gearing up for field trials on vegetables. Listed below are our research trials for this growing seasons addressing the need of the agriculture community. For more information and/or collaboration contact: bpoudel@arizona.edu
 
Soil amendments for Fusarium wilt in lettuce
We will be conducting trials using different soil amendments available in market to see their effect on fusarium wilt of lettuce. Last years results available. 
https://doi.org/10.1094/PDMR16
 
N. Singh, M. Porchas, J. Furr and B. Poudel-Ward (2022). Evaluation of different soil amendments to manage Fusarium wilt of lettuce in Yuma, AZ, 2021. PDMR: Volume 16. 
. Funded by Specialty crop block grant.

Downy mildew in Lettuce

We will conduct trial on downy mildew of lettuce this year as well.


Sclerotinia drop of Lettuce


We will continue to do field trials on sclerotinia drop of lettuce on both species S. sclerotiorum and S. minor.

Powdery mildew of lettuce

We will continue with field trials on powdery mildew of lettuce.

Downy mildew of Spinach 
Downy mildew of spinach field trials won’t start until January of next year. But we are requesting industry reps to contact us ahead of time.     Protocols for lettuce trials: Please submit by end of October. Material has to be sent in mid December. We start applications on first week of January.  For more information contact Bindu Poudel-Ward (bpoudel@arizona.edu).

Over the last couple of years, we identified and developed two high speed, precision spot sprayers to apply herbicides to weeds with minimal off-target spray while traveling at speeds that are viable for commercial vegetable farming operations (2 mph). The first is a spray assembly designed for controlling in-row weeds that are close to crop plants (1-cm spot spray resolution). The second is a high precision (sub-centimeter spot spray resolution) sprayer designed for spot spraying cotyledon stage weeds in spinach and leaf lettuce crops. We tested the device in the laboratory and found that weed control efficacy was greater than 95% (3 species), percentage of off-target spray was less than 3% and no crop injury was observed. The work was presented at the 2021 California Weed Science Society Annual Meeting. Click here or on the image below ) to view the presentation and see video of the devices in action. 

We are now working towards developing a high precision, automated/robotic weeding machine for vegetable crops. This fall, Evan McGinnis, Biosystems Engineering Ph.D. candidate, initiated work to develop AI-based imaging software for detecting and targeting weeds. Once developed, the software will be integrated with the precision spot sprayer and tested in the field. Stay tuned for updates!

Acknowledgements

This work is supported by the Arizona Specialty Crop Block Grant Program and the USDA NIFA Specialty Crops Research Initiative USDA-NIFA-SCRI-004530. We greatly 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. Images from “Centimeter Scale Resolution Sprayer for Precision In-Row Weed Control” presentation given at the 2021 California Weed Science Society Annual Meeting. Click here or on image to view the presentation.

We published this booklet last July. Please let us know what you think by responding our five questions in the link provided below. The first 25 respondents WILL RECEIVE a copy of the guide. Additionally…first five to take the survey and ID the weeds in the cover of the booklet will also get a Navy Blue UA Vegetable IPM HAT.

ANSWER 5 QUESTIONS HERE

There are abundant resources for weed identification of mature plants. These include very complete guides such as “Weeds of California and Other Western States” by Joseph DiTomaso published by University of California. “An Illustrated Guide to Arizona Weeds” by Kittie F. Parker with excellent drawings by Lucretia Breazeale Hamilton. There are also several phone apps for weed identification. However, the cotyledons of weeds frequently have a different shape than the true leaves, which makes identification of seedlings difficult for some species. The purpose of this pocket booklet is to provide a quick reference with good images that can be carried in your truck to help you identify the most common broadleaved weeds in Southwestern and Central Arizona.

The method for identification presented is not by using a dichotomous key or answering complicated questions about the species. The idea is to leaf through the booklet and find images that match plants you see in the field. If there are unusual characteristics, we note them in our comments for each weed. Here is a link to the guide in PDF format: HERE

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts increased in most locations over the past 2 weeks; but remain average for this time of the season. 
 
Beet armyworm:         
Trap counts remain low in all locations, increased slightly, but remain below average for late season.
 
Cabbage looper:         
Cabbage looper trap counts increased in all locations, but still below average for late season.
 
Diamondback moth:    
Adult activity increased in some locations in the past two weeks. Overall, activity is below average for this time of year. 
 
Whitefly:                       
Adult movement remained low in all locations consistent with previous seasons.
 
Thrips:                         
Thrips adult movement increased in all locations recently particularly in the Tacna/Roll are. Activity is well below average for late season.
 
Aphids:                        
Aphid movement low in most locations but increased slightly in Gila Valley. Trap captures well below average for this time of the season.   
 
Leafminers:                   
Adult activity increased in many areas, and below average for this time of season.