It’s hard to believe it’s been 10 years since the bagrada bug, Bagrada hilaris, first invaded the desert.  Outbreaks of the invasive pest species occurring in the first few years were quite disruptive, causing significant damage to Cole crops and excessive insecticide spraying. As a new pest, many PCAs and growers struggled to control the pest, but after a few years, populations subsided significantly. I think most would agree that the bagrada pressure has been relatively light the past few years.   In fact, recent infestations have been as light as we’ve seen since the bagrada bug first occurred on desert Cole crops.  We’re uncertain why populations have declined over the past few years but may in part be a due to aggressive preventative control measures, use of insecticide seed treatments, improved bagrada control in nurseries and greenhouses, and impact of natural enemies (e.g., predators, pathogens) in non-crop landscapes. Slightly higher numbers observed last fall were likely due in part to the wet winter experienced in 2018-19.

To document changes in the severity of bagrada bug infestations on direct-seeded and transplanted cole crops and the intensity of chemical management, we have annually surveyed growers and PCAs from Yuma, Maricopa and Imperial counties since 2010. We recently conducted our annual survey and results show that since 2010 the cole crop industry has experienced widespread bagrada bug infestations throughout the desert from September into November, although recent years have been less intense. Last fall (2019) was one of the lighter years we’ve seen to date, but higher than the previous four seasons.  Based on seasonal population abundance studies of adults infesting non-treated broccoli plants at the Yuma Ag Center (see graph below), bagrada bug infestations remain    relatively low compared to the first few years following the initial 2010 outbreak.

Estimates of stand losses from bagrada bug infestations at stand establishment in both direct-seeded and transplanted crops have decreased considerably over the past 10 years and remained relatively low during the 2019 fall growing season, although slightly up from last season. Plant injury, defined as plants with multiple heads, forked terminals, and/or blind terminals resulting from bagrada feeding, was also low relative to 2010 for both direct-seeded and transplanted crops. These reported losses are consistent with stand losses and plant injury measured in trials conducted at the Yuma Ag Center over the past ten years.  Insecticide usage to control this pest remain down in 2019, where the percentage of acreage treated was comparable to the previous two seasons.  Pyrethroids remain the primary product used for controlling bagrada bug adults either via chemigation or with foliar spray applications. Based on survey results, products that have contact activity appeared to provide the most effective control against bagrada adults on both direct-seeded and transplanted cole crops.  Results from the survey also showed that over half of direct seeded broccoli was treated with clothianidin (Nipsit®) in 2017, but a significant decrease in the Nipsit® acreage and number of PCAs using the product was reported in 2018.  NipsIt® usage was up slightly in 2019, and those who used the product in 2019 reported it was extremely effective in controlling bagrada bug adults. Laboratory bioassays to measure insecticide susceptibility were conducted in 2020 and compared to baseline data collected in 2010. Results showed that the bagrada bug population collected in 2020 remain susceptible to Bifenture, Warrior II, Venom and Lannate. Overall, the results of the PCA survey are consistent with results obtained in research trials conducted at the Yuma Agricultural Center over the past ten years.  

June 10, 2020
Name the insect pest

In a world of increasing costs associated with about everything we do, there is some good news in the international fertilizer market.  In response, we can begin to anticipate changes in fertilizer costs at the field level.
 
International fertilizer prices began to experience sharp increases in 2021 due to a series of supply shocks, weather patterns, fertilizer production plant closures, an imperfectly competitive and shallow market structure, and a series of policy changes that resulted in significant price volatility and a drop in fertilizer affordability.  Since then, higher prices of fertilizers have been a challenge globally and it has certainly impacted our crop production systems of the desert Southwest (Figure 1).
 
Some of the fertilizer and grain trade flow issues we have recently experienced developed in relation to the Russian conflict with Ukraine that began in February 2022 and the resultant tensions in the region.  Economic sanctions have been imposed on Russia, inflation has been increasing fertilizer prices and transportation, and other pandemic-related complications have contributed to transportation logistical challenges.  But the Russian-Ukrainian conflict has not been the sole cause of the international fertilizer price increases.
 
Some production and supply reductions experienced in the European, Chinese, and Russian segments of the global fertilizer industry have been caused by sharp increases in production costs.  For example, prices of natural gas and ammonia in Europe, Russia, and in China have increased along with high prices for coal which have created reductions in electricity production and consequential disruptions in the fertilizer industry, which is energy intensive.  The Chinese reduced fertilizer exports in 2021 because of these reductions in fertilizer production and supply (Figure 2; Raghuveer and Wilczewski, 2022).
 
Despite the difficulties in the international fertilizer market in the past 18 months, there are some promising recent trends.  In the past several months international fertilizer prices have come down to levels close to those experienced in early 2021.  Even considering the recent declines in the international fertilizer prices, they 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; Quinn, 2023).  
 
By the end of July 2023, anhydrous ammonia (82-0-0) was 6% lower in late July than a month earlier with an average price of $713/ton.  Among the other major fertilizer materials, diammonium phosphate (DAP) had an average price in late July of $807 per ton, monoammonium phosphate (MAP) $812/ton, potash (primarily muriate of potash, KCl) was $608/ton, urea (45-0-0) $596/ton, liquid ammonium polyphosphate (10-34-0) $717/ton, urea ammonium nitrate (UAN28) $385/ton, and a higher N concentration form of UAN32 was $457/ton.  
 
It is important to note that 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 the most common dry form in the market.  
 
On a percentage basis, urea (46-0-0) is 29% less expensive than a year ago, potash fertilizers are now 31% lower, urea ammonium nitrate (UAN32) is 34% less expensive and another form with 28% N (UAN28) is 36% lower, and anhydrous is 50% less expensive compared to last year.  Monoammonium phosphate (11-52-0) is now 22% lower and diammonium phosphate (DAP) 18-46-0 and ammonium polyphosphate (10-34-0) are 20% lower in price.  
 
Urea (46-0-0) has recently dropped below the $600/ton to $585/ton for the first time since late September 2021.  Anhydrous ammonia (82-0-0) has had an average price recently of $713/ton, which is down about 9% in price from April 2023.  Muriate of potash (KCl, 0-0-60) had an average price in the past month of $608/ton, ammonium polyphosphate (10-34-0) average price has been $717/ton, and urea ammonium nitrate (UAN-32, 32-0-0) average price has been $457/ton this past month.  Urea ammonium nitrate (UAN-28, 28-0-0) price has dropped to an average of $385/ton.
 
When considering nitrogen (N) fertilizer prices in terms of the price per pound of N, recent urea (45-0-0) prices averaged $0.65/lb.N, anhydrous ammonia (82-0-0) $0.44/lb.N, urea ammonium nitrate (UAN28) $0.69/lb.N and urea ammonium nitrate with 32%N (UAN32) is now $0.71/lb.N.
 
Hopefully, the trajectory of fertilizer prices experienced in the past 18 months will continue and the average costs may return to levels close to 2021 (Figure 1).  However, international logistics in the fertilizer industry, including shipping, transfer, and distribution of fertilizer cargo continue to be very important in the fertilizer markets and any projections for the future.  Market and transportation issues in the Black Sea region and limitations in the exportation of fertilizer materials from the western ports of Canada due to labor issues, primarily affecting potassium fertilizers, are still important factors to watch.

Figure 1.  Average weekly retail prices for anhydrous ammonia (82% N), for 2021,
2022, and through 21 July 2023.  Source: DTN/Quinn, 2023.



Figure 2.  General relationship between weekly natural gas and ammonium
fertilizer prices, 2020-2022.  Source:  T. Raghuveer and W. Wilczewski.  U.S.
Energy Information Administration.

References:
Quinn, R. 2023.  DTN Retail Fertilizer Trends: Fertilizer prices moving in two directions. DTN Newsletter, 26 July 2023. https://www.dtnpf.com/agriculture/web/ag/crops/article/2023/07/26/urea-drops-600-per-ton-first-time
 
T. Raghuveer and W. Wilczewski.  2022.  U.S. ammonia prices rise in response to higher international natural gas prices.  U.S. Energy Information Administration.  https://www.eia.gov/todayinenergy/detail.php?id=52358#

This study was conducted at the JV farms at Gila Valley. Lettuce variety ‘Guapo’ was seeded, then sprinkler-irrigated to germinate seed on September 19, 2023, on double rows 12 in. apart on beds with 42 in. between bed centers.  Rest of the irrigation 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, which contained two 25 ft rows of lettuce. Plants were thinned on October 9, 2023 at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied by incorporating in soil before seeding or with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.

 
Fusarium wilt (caused by Fusarium oxysporum f. sp. lactucae ) rating was done in the field by observing the typical symptom of lettuce wilt. Confirmation was done by cutting the cross section of roots. Disease scoring/rating was done on December 6, 2023. 
 
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. The disease pressure was extremely high in 2023, and most treatments showed little or no control against the disease. The treatments that showed some activity were Bexfond, Cevya, Rhyme, and Serifel. Plant vigor was normal and phytotoxicity symptoms were not observed in any treatments in this trial.

Over the last couple of years, we developed a prototype steam applicator for injecting steam into the soil prior to planting. The concept behind soil steaming is similar to soil solarization - heat the soil to levels sufficient to kill soilborne pathogens and weed seeds (typically 140 °F > 20 minutes). The device is principally comprised of a 63 BHP steam generator mounted on an elongated bed shaper (Fig. 1). The apparatus applies steam via shank injection and from rectangular ports on top of the bed shaper. After cooling (< ½ a day), the crop is planted into the disinfested soil.

Trial results have been very promising and reported in previous UA Veg IPM articles. In brief, the multi-year studies have shown that soil steaming provides excellent weed control (>90%), suppresses problematic soilborne diseases (Fusarium wilt of lettuce> 50%, lettuce drop > 70%) and increases crop yields (>24%).

This season, we would like to demonstrate the technique to interested growers. In addition to obtaining grower feedback on the viability of soil steaming, a second objective would be to validate our small plot research results at the field scale level. The machine can be adjusted to work with most bed configurations including 40”, 42”, 80” and 84” beds, and work with any crop, including organic crops (soil steaming is organically compliant). So far, the device has been successfully tested in iceberg lettuce, romaine, baby leaf spinach and carrot crops.
If you are interested in an on-farm demo of soil steaming, please let me know. I’d be happy to work with you.

Fig. 1. a) Band-steam applicator principally comprising a 63 BHP steam generator
mounted on a bed-shaper applicator sled. Steam applicator sled b) top view and
c) bottom view. Click here or on the image above to see the device in action.

Burndown herbicides are used to kill emerged weeds prior to planting lettuce. Some of the species we have are very hard to kill. Therefore, these weeds would have to be controlled using selective herbicides after the crop has emerged.   
Some of the products we have available are glyphosate (Roundup), paraquat (Gramoxone), oxyfluorfen (GoalTender), carfentrazone (Aim,Shark), Pyraflufen (ET), and pelargonic acid (Scythe). There are other products that are being developed such as the S3100 from Valent USA.
Herbicides that can be used up to just before crop emergence are Roundup, Paraquat and Scythe, these provide no residual weed control. ET has an interval of 1 day following preplant burndown application for leafy vegetables. AIM herbicide also requires for some crops (tobacco) 1 day following preplant burndown¹. Oxyfluorfen does not bind strongly to soil but stays active for a long time and requires ninety days after application for the low rate and 120 days for the high rate prior to planting lettuce⁴. It forms a layer on the soil surface that weeds contact as they emerge. If this barrier is destroyed by machinery traffic weeds will not be controlled.
Roundup is a systemic and with a Koc (sorption coefficient) factor of 24,000 adheres very strongly to the soil. So, it is active only on growing plants, but once its bind to the soil is inactive.
Paraquat also adheres good to the soil with a Koc of 1,000,000, so coverage is important for best weed control.  
There is a project through the IR-4 program to add the use of glufosinate as a Pre-Plant burndown on spinach, lettuce, broccoli, cabbage, and mustard greens. Hopefully this addition to the label will provide a new tool for our growers in Arizona and other States³

1. https://www.cdms.net/ldat/ld5L1003.pdf
2. https://cales.arizona.edu/crops/vegetables/advisories/docs/herbicide_injury.pdf
3. https://www.ir4project.org/
4. https://ag.arizona.edu/crops/vegetables/advisories/more/weed140.html

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 21, Oct 16, 2024

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts increased in most traps; about average for early October.

Beet armyworm: Trap counts increased in most areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts still most locations, below average for this time of the season.

Diamondback moth: Adult activity increasing, particularly in the Yuma and Dome Valleys.  Above average for this time of season.

Whitefly: Adult movement increasing Tacna, Dome Valley and Yuma Valley; overall about average for early October.

Thrips: Thrips adult movement picking up in all areas, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; about average for early October.