With the days getting longer and temperatures gradually warming, 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 suggests that temperatures will be in the upper 60’s with moderate nighttime lows in the mid-40’s for the next two weeks. Assuming the weather service is correct, these conditions may be ideal for aphid population growth.  Aphid population growth in the desert produce is optimal at average temperatures of 55-60 °F. Similarly, with the rainfall we experienced in late December, I would keep an eye out for aphid pressure to start picking up on your lettuce, celery, spinach and cole crops.  Previous research has shown us that aphids tend to be more abundant during warm, wet winters. Note:  Rain has been forecasted for this week.
 
Aphid flights are ahead of schedule compared to the past few seasons (see graph below). Trap captures of winged aphids peaked last week and were particularly heavy in the North Gila and Yuma Valleys.  There have been several reports of green peach aphids showing up in both conventional and organic produce in the past several weeks, 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 aphids too; we’ve confirmed reports of small colonies on lettuce in Wellton in November, and in the Gila Valley this week.    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 the presence of aphid colonies on 5-10% 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.  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 sites:  

• Keys to Aphid Management in Leafy Vegetables 
• Aphid Management on Desert Produce_2024 
• Aphid ID Guide

 

This time last year we were experiencing extremely high fertilizer prices that were continually rising.  Fertilizer prices had been steadily increasing throughout 2021 and then experienced an acceleration after the Russian invasion of Ukraine in February 2022.  Throughout the desert Southwest and across the nation, high prices have continued for fertilizers used in crop production agriculture over the past year.  Now in early 2023 fertilizer prices are starting to decline but are still relatively high compared to prices two years ago.  These patterns are shown in Figure 1.
 
There are at least four important lessons or messages from these recent experiences with global fertilizer prices and the impacts at the field level in crop production systems.  First, many people have come to recognize that among global nitrogen (N), phosphorus (P), and potassium (K) fertilizer producers China, Russia, and Belarus are major players and are consistently in the top 10 (Figure 2).  Our awareness has been heightened in response to the diminished supply available to U.S. markets from these three nations in the past year.  The U.S. ranks fourth in overall N, P, and K fertilizer production.
 
Secondly, as fertilizer use has increased in many parts of the world in the past 60 years, the U.S. now represents only 10% share of the global use of N, P, and K fertilizers (Figure 3).  
 
The third point that has been emphasized and has become increasingly clear to the crop production industry, is the connection between fertilizer production input costs, particularly natural gas, and fertilizer prices (Figure 4).  Fertilizer production facilities require a large amount of energy to convert the raw chemical materials into their applicable farm-use state. This is very important in terms of N fertilizers. 
 
Regarding prospects for global fertilizers, experts in the industry have the common variance in points of view but there seems to be a general agreement that higher prices have been a function of reduced supply and that was further exacerbated by the Russia-Ukraine war, the loss of a major port for Belarus potash fertilizer, and the P fertilizer supply constraints from China (Baffes and Koh, 2023).
 
These pressures are not going away soon, but the impacts have diminished in recent months.  The constraints on supplies of P and K fertilizers are expected to continue for quite some time into the future.  Price reductions have been most notable for N fertilizers, primarily due to lower natural gas prices in Europe compared to 2022.
 
Crop Nutrient Management
The fourth point of emphasis regarding fertilizer prices and desert crop production systems has been the shift towards more conservative management of fertilizers in the field.
 
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.   The 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, an assessment of plant-available forms of the nutrients present in the soil by evaluating soil tests with appropriate indices is a good step in the development of a more efficient nutrient management program.  Then splitting nutrient applications, particularly mobile nutrients such as N in line with crop uptake and utilization patterns are good steps towards higher fertilizer use efficiency by the crop.  Thus, timing, methods, and rates of nutrient applications are critical (i.e., 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.
 
References:
Baffes, J, W. C. Koh.  2023.  Fertilizer prices ease but affordability and availability issues linger.  5 January 2023, World Bank.  https://blogs.worldbank.org/opendata/fertilizer-prices-ease-affordability-and-availability-issues-linger
 
Crawford, A, F. Jomo, E. Elkin, and M. Bristow. 2023.  World’s fertilizer market in turmoil.  Bloomberg, Farm Progress, 20 February 2023.  https://www.farmprogress.com/crops/world-s-fertilizer-market-in-turmoil
 
Quinn, R. 2023.  DTN retail fertilizer trends.  DTN Progressive Farmer, 15 March 2023.  
https://www.dtnpf.com/agriculture/web/ag/crops/article/2023/03/15/anhydrous-uan-move-even-lower?referrer=NLSnapshot

Figure 1.  Average weekly retail prices for anhydrous ammonia (82% N), for
2021, 2022, and through 10 March 2023.  Source: DTN/Quinn, 2023.


Figure 2.  Ranked nitrogen, phosphorus, and potassium fertilizer production by
country.  (FAO and Bloomberg graphics).  Crawford et al., 2023.



Figure 3.  Pattern of U.S. share in the global nutrient market since
1961.  Source: Farm Bureau.


Figure 4.  Fertilizer input cost trends, 2019-2022.  Source: Bloomberg; World
Bank.  Baffes and Koh, 2023.

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%). Variety: Deluxe (HMX2595) was seeded, then sprinkler-irrigated to germinate seed on March 20, 2024on 84 inches 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. 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. 

Spray treatments were done on 05-21-2024, 05-31-2024, 06-07-2024 and 06-14-24. Powdery mildew was first seen on 06-05-24. Please see excel file for additional details.  

Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-17-2024 by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 1 = one to two mildew colonies on leaves  ;2 = powdery mildew present on one quarter of leaves; 3 = powdery mildew present on half of the leaves; 4 = powdery mildew present on more than half of leaf surface area ; 5 = powdery mildew present on entire leaf. These ratings were transformed to percentage of leaves infected values before being statistically analyzed.

The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. Quintec, Merivon, Tesaris, Luna Sensation, and V6M-5-14 V gave the best disease control. Phytotoxicity symptoms were not noted for any treatments in this trial.

ANR Webinar 10/17 click link for details.

With the advent of low-cost computing systems that can identify and locating crop and weed plants in real-time, there’s been an explosion in the interest, investment and development of technologies for robotic/automated weed control. A quick internet search will reveal over 50 companies or university research groups working in this space. You are probably familiar with many of these as they are domestically based and have been discussed in previous articles, but there are also numerous efforts being made in Europe that may be of interest. One of these is highlighted here. In future articles, I’ll discuss additional technologies. 
Andela Techniek & Innovatie¹ is a Dutch company who appears to be making good progress with an innovative robotic weeding machine (Fig. 1). The solar powered device spans 29.5 feet and is equipped with 12 robotic delta arms for removing in-row weeds (Fig. 2). A camera-based imaging system is used to differentiate crop plants from weeds and provide coordinates of targeted weeds to the delta arms. Each delta arm is equipped with an end-effector that uses heat to kill the weed when it comes into contact with it. A company video showing the device operating in carrot and onion crops can be found by clicking here or on the images below. 
Stay tuned!

 

Fig. 1. Andela Techniek & Innovatie1 solar powered robotic weeding machine. (Photo credits: Andela Techniek & Innovatie)


Fig. 2. Delta arms and end effector of Andela Techiek &
Innovatie¹ robotic weeding machine. (Photo credits:
Andela Techniek & Innovatie)

Do you know the botanical families of all the small acreage specialty crops grown in the low desert?
The family is an important factor in deciding what type of herbicides can be used for weed control in our crops. For some of us it has been difficult to keep track of the families. I found a table published in this Newsletter by our Applied Weed Science maestro Barry Tickes. 

Hope you like the chart with the botanical families of many of these crops and herbicides that might be used on them.

Botanical Family	Crops	Possible herbicides (check label)
Brassica	Bok Choy, Napa, Mizuna, Kale, Kohlrabi, Turnip Greens, Mustard, Tatsoi, Arugula, Radish, Daikon	Prefar, Trifluralin, Dacthal, Stinger, Poast, Select
Umbelliferae	Cilantro, Celery, Coriander, Parsley, Dill, Parsnip, Fennel	Prefar, Lorox, Poast, Prometryne
Aster	Endive, Escarole, Chicory, Radicchio	Prefar, Trifluralin, Kerb, Fusilade, Poast, Select
Amaranth	Spinach, Chard, Beets	Roneet, Dual Magnum, Poast, Select

 

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 17, Aug 21, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts decreased areawide; about average to previous years.
 
Beet armyworm:         
BAW moth counts are up in south Yuma valley and Dome valley; about average for August

Cabbage looper:           
Cabbage looper numbers are low consistent with previous years and higher temperatures.
 
Diamondback moth:      
DBM moths were not caught in any trap; average for this time of the year.
 
Whitefly:                      
Adult movement continues to decrease, average for this time of the year.
 
Thrips:                          
Thrips adult activity continues to decline, average for August.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity declining and average for August.