Every season is unique, and this fall was no different in terms of insect pressure on desert produce crops. A quick look at both recent and historic data on pest abundance recorded from our University of Arizona research plots and areawide trapping and sampling suggests that insect pressure was unusual for several pests. For a look at the data see Fall Pest Abundance on Desert Produce and Melon Crops
 
Whitefly/CYSDV:   Whitefly populations in fall melons were lighter this fall compared to previous years, and areawide, adult movement was below average. CYSDV incidence in cantaloupe fields was much lower than experienced last fall which was unusually high in the Roll/Tacna and Texas Hill areas due to about 300 acres of abandoned watermelons which were highly infested with whiteflies and viruses. Virus incidence in these locations in 2022 was below 10%. However, CYSDV on average was estimated at about 50% in fields produced in the Yuma Valley, where historically virus has been heavier. Whitefly nymph abundance was light in produce crops at YAC in 2022, and apparently light throughout the growing area based on no reports from PCAs.
 
Beet armyworm (BAW), cabbage looper (CL), and corn earworm (CEW):  BAW and CL pressure in the early fall was very high, although not to the levels seen in 2020. BAW pressure subsided in mid-September, but CL pressure was heavy until early November. Worm pressure has been very light since then, likey due to the below average temperatures in November. Trap catches for both BAW and CL were below average. CEW trap catches peaked in mid-October and failed to be much of an issue at harvest in most locations. However, we did receive reports of CEW at harvest in a couple of fields of lettuce in Dome Valley. 
 
Diamondback moth (DBM):   DBM was not a problem again for local desert growers in 2022. PCAs began reporting the presence of larvae in late October but pressure never built up much after that. Areawide pheromone trapping showed that DBM moth activity began later this fall and on average, much lower than we typically find. Following the storm on Dec 3, we experienced a significant spike in trap counts throughout the area suggesting that populations may be migrating in from coastal areas.  At YAC, the larval populations were light compared to previous years, and field efficacy trials in broccoli indicated that this population was very susceptible to all industry standard insecticides. 
 
Aphids     Flights of winged adults have been lighter than most years. Prior to the recent storm (Dec 3),  trap counts have been very low, but increased significantly last week in the Yuma and Gila Valleys.  We did receive reports of green peach aphid nymphs colonizing lettuce and brassica crops in early November, but reports have been light for the past several weeks.  No reports of lettuce or foxglove aphids to date. Aphids might be light this spring.
 
Western Flower Thrips (WFT) / INSV:  WFT pressure on non-treated lettuce plants at YAC was lighter than the past several seasons.  Areawide trapping showed that adult activity was well below average as well, but traps placed on edges of alfalfa, cantaloupe and lettuce fields showed that WFT activity was much higher in melons. Adult movement peaked in all crops around early-mid October, particularly in melons at harvest. In fall lettuce, adult and larvae densities on plants was lower than what we found in fall 2021, and unusually low during November. Although INSV infected transplants were again detected in October in Tacna, Roll, and Wellton, to date virus incidence in direct-seeded lettuce remains almost non-detectable in these areas.  Caution: If we experience a La Nina weather pattern as predicted, WFT populations may rapidly begin building in January. Be vigilant in your WFT management this winter/spring. 
 
Have a Merry Christmas, and we’ll visit again next year!

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. 12, No. 18, Sep 8, 2021.
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts increased in the past two weeks particularly in Wellton and Roll.  
 
Beet armyworm:         
Trap counts beginning to increase in most locations especially in dome Valley and the south Yuma Valley.
 
Cabbage looper:          
Cabbage looper increased in all locations particularly in Wellton, Dome and N. Yuma Valleys consistent with reports of eggs in the in the field.
 
Whitefly:                      
Adult movement increasing in all locations and particularly in Dome/Wellton; about average for this time of year. 
 
Thrips:                         
Thrips adult movement remains about average for early September.
 
Aphids:                         
Aphid movement has been absent since early June typical with high summer temperatures, and the monsoon flow.  
 
Leafminers:                  
Adult activity remains similarly low, above average for this time of season.
 
Diamondback moth:   
First record of DBM adults since early June. Are appearing sooner than last season, likely from high altitude winds associated with Tropical Storm Nora experienced last week.