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

 

In the past year we have experienced huge fluctuations in the global fertilizer markets.  In 2022, fertilizer shortages developed and the price of fertilizers increased up to 180% in some cases.  

 
These large fluctuations have been largely due to changes in trade flows with Russia because of the tensions in the region, sanctions imposed on Russia, inflation, and other pandemic-related complications with transportation logistics.  Collectively, expensive fertilizer prices have been a challenge globally and certainly in our crop production systems of the desert Southwest.
 
Recently, several retail fertilizers have varied significantly in the market trends.  For example, in May 2023 about half of the major retail fertilizers are higher compared to April prices and the other half has lower prices than last month (Quinn, 2023).
 
Urea (46-0-0) has gone up 6% in retail markets since last month with an average price of $664/ton.  A few weeks ago, urea was below $600/ton for the first time since late 2021.  Similarly, diammonium phosphate (18-46-0), monoammonium phosphate (11-52-0), and urea ammonium nitrate (32-0-0) had an average the past month of $517/ton.
 
In contrast, anhydrous ammonia (82-0-0) has had an average price recently of $910/ton, which is down about 9% in price from April 2023.  Several other major fertilizers have been lower in price the past month.  Muriate of potash (KCl, 0-0-60) had an average price in the past month of $627/ton, ammonium polyphosphate (10-34-0) average price has been $739/ton, and urea ammonium nitrate (UAN-32, 32-0-0) average price has been $423/ton this month.
 
Note that several of the major fertilizer materials come in different forms.  For example, urea ammonium nitrate (UAN) is 28% N in some materials and 32% N in another common form.  Also, monoammonium phosphate (MAP) can have N concentrations of 10-12% and P₂O₅ concentrations of 48-61% with 11-52-0 being probably the most common form in the market.
 
Considering the overall trends in the past few years, international fertilizer prices have been generally decreasing since the summer of 2022.  Today, international fertilizer prices are back in a range close to early 2021.  International fertilizer prices are not expected to drop below pre-pandemic levels, primarily due to global inflation that generates an increase in production and transportation costs (Figure 1).
 
Several expert sources in the fertilizer industry are projecting a drop in international fertilizer prices in the coming months by approximately 50% of the prices experienced last year.   Accordingly, many fertilizer importers are waiting to ship to markets and farmers are often waiting and watching for the projected drop in fertilizer prices to materialize before purchasing (Schnitkey et al., 2023).
 
Despite the high degree of volatility in international fertilizer markets and the limited availability of fertilizers in some crop production sectors that have recently been experienced, it is expected that the downward trends will continue.
 
Looking ahead, many experts in the international fertilizer industry are recommending for producers to not wait until too late to purchase fertilizers for upcoming crops, utilize economies of scale when purchasing fertilizers materials as much as possible, and of course watch the trends in fertilizer markets.  International logistics in the fertilizer industry, including shipping, transfer, and distribution of fertilizer cargo is proving to be very important in realizing a more stable fertilizer market for the future.

Figure 1.  Example of fluctuations in fertilizer prices per ton of material from
January 2021 through March 2023.  Source:  Schnitkey et al. 2023

References:
Schnitkey, G., N. Paulson, C. Zulauf and J. Baltz. 2023. Fertilizer Prices and Company Profits Going into Spring 2023. farmdoc daily (13):36, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, 28 February 2023.
 
Quinn, R. 2023.  DTN Retail Fertilizer Trends: Fertilizer prices moving in two directions. DTN Newsletter, 17 May 2023. https://www.dtnpf.com/agriculture/web/ag/crops/article/2023/05/17/fertilizers-moving-two-directions

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.

 Fig. 1. Finger weeders removing a large, in-row Palmer Amaranth plant in cotton – slow motion video. (Video credit: Kyle R. Russel, Texas A&M University. Cultivator design and setup credit: Carl Pepper, Lubbock, TX). Click here or on the image to see the video. 

Surveying the Yuma area, we have observed a lot of Hairy Fleabane (Conyza bonariensis) and received calls from PCA's regarding this weed and its control. 
We have observed that the application of Glyphosate is not showing good efficacy in controlling this species in parts of Yuma and Phoenix area. 
Resistance to glyphosate has been reported in some grain growing areas of Queensland and northern New South Wales and other cropping regions across Australia ⁽¹⁾ as well as Spain ⁽²⁾.
Other cases of resistance to other herbicides such as paraquat, and 2,4-D have been confirmed ⁽³⁾.
In the International Herbicide Resistance Weed Database it is reported that in Switzerland that both Conyza canadiensis (Horseweed) and Conyza bonariensis (Hairy Fleabane) presented resistance to a HRAC Group 9 herbicide last year. We found resistance reported in California only and not in Arizona ⁽⁴⁾.

Some of our PCA amigos and field technicians have reported having problems finding a good treatment for fleabane due to possible glyphosate resistance. We included Glufosinate and Embed Extra in a trial last year. The images below show good results of an application of Rely at a high rate (82floz) with two applications at a 2-week interval. The second picture shows the efficacy of Embed Extra (2 pt.) following the same application schedule. Weeds were ~2-3” at the time of application. Some growers have reported good results with glufosinate in Waddell AZ. Sharpen has also been used by Yuma citrus growers.  
A study showed that plants grown at 90% relative humidity presented more translocation of glufosinate than those grown at 35%. Relative humidity had greater effect than temperature on glufosinate toxicity to Palmer amaranth, redroot pigweed, and common waterhemp ⁽⁵⁾. In a trial conducted by Barry Tickes from UA nutsedge control was better in an August application with a ~40% RH than a June application with ~20% RH.
As always please check labels and registration before using these treatments.

Figure 1. Hairy fleabane control with Glufosinate


Figure 2. Hairy Fleabane control with Embed Extra

References:

1. https://bnrc.springeropen.com/articles/10.1186/s42269-020-00316-w

2. https://cdnsciencepub.com/doi/10.1139/cjps-2018-0254

3. https://bioone.org/journals/weed-technology/volume-35/issue-4/wet.2021.11/Cross-resistance-to-diquat-in-glyphosate-paraquat-resistant-hairy-fleabane/10.1017/wet.2021.11.short

4. https://www.weedscience.org/Pages/Species.aspx

5. Coetzer, E., Al-Khatib, K., & Loughin, T. (2001). Glufosinate efficacy, absorption, and translocation in amaranth as affected by relative humidity and temperature. Weed Science, 49(1), 8-13. doi:10.1614/0043-1745(2001)049[0008:GEAATI]2.0.CO;2

Area wide Insect Trapping Network   VegIPM Update, Vol. 14, No. 22, 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.