Jul 26, 2023Trends in Insect Losses and Management on Desert LettuceTo contact John Palumbo go to: jpalumbo@ag.Arizona.edu
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.
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#
In the past few weeks we have seen increase in cucurbit samples submitted to the plant disease diagnostic clinic infected with bacterial wilt. PCAs have also reported increase in number of cucumber beetle in the fields.
Bacterial wilt is a common occurrence in commercial fields and residential gardens. This destructive disease can potentially result in complete crop loss even before the first harvest. Hosts Cucumber and muskmelon (cantaloupe) are highly susceptible; squash and pumpkin are less susceptible; watermelon is resistant.
Initially, individual leaves or groups of leaves turn dull green and wilt (Figure 1), followed by wilting of entire runners or whole plants. At first, plants may partially recover at night, but as disease progresses, wilt becomes permanent. Collapsed foliage and vines turn brown (necrotic), shrivel, and die (Figure 2). Wilt symptoms may be noticeable in as few as 4 days from infection on highly susceptible hosts but can take up to several weeks to become evident on crops that are less susceptible. Plant growth stage can also affect disease progress, which is more rapid on young, succulent plant tissues.
The diagnostic feature for this disease is the emission of a slimy, sticky ooze (exudate made of polysaccharides and bacterial cells) from cut stems. Field diagnosis can be confirmed using a simple “bacterial ooze test.” With a sharp knife, cut through a wilted (but not dead) vine; use a section near the crown (Figure 3A). Touch the cut ends together, and then slowly pull them apart. Fine thread-like strands of bacterial ooze will be drawn out (Figure 3B) when bacteria are present. This test works well for cucumber and muskmelon but is less reliable for squash or pumpkin. If this disease is present, a cloudy string or mass of bacterial ooze will flow into the water from the cut stem pieces (Figure 3C).
Bacterial wilt is caused by Erwinia tracheiphila; striped and spotted cucumber beetles (Fig 4 and 5) serve as vectors, carrying the bacterium from plant to plant during the growing season. The life cycles of the bacterial wilt organism and its vectors are closely associated, and bacterial wilt is directly correlated to striped and spotted cucumber beetle populations. These beetles hibernate through winter under leaf litter and in other protected sites; all the while, the bacterial wilt pathogen overwinters within the gut of the striped cucumber beetle. The beetles become active once temperatures remain above 55°F in spring. As soon as cucurbit seedlings begin to break through the ground, the beetles begin to feed on cotyledons and later feed on leaves, stems, and flowers. Striped cucumber beetle larvae also feed on root systems, causing damage that can result in wilt. The bacterial wilt organism is deposited through beetle mouthparts and the frass deposited onto/ into wounds created during beetle feeding. Once the bacterium invades a plant’s water conducting vessels (xylem), it spreads rapidly throughout the plant. The matrix of bacteria and ooze obstructs water movement in the xylem vessels, which causes wilt symptoms. Further spread of the pathogen occurs when beetles feed on diseased plants and then feed on nearby healthy plants. Close to harvest, a second generation of striped cucumber beetle may acquire the bacterium while feeding on infected plant tissues. Fall-planted cucurbits may be infected by this generation. These late-season adults will overwinter with the live bacterium in their gut and possibly transmit the pathogen to young plants the next spring. The bacterium cannot survive in infected plant debris from one season to the next.
Prevention of bacterial infections is dependent upon preventing cucumber beetle vectors from feeding on cucurbit plants. Early protection is critical for long-term disease management, which should begin as soon as seedlings emerge or when plants are transplanted into fields or gardens. Once it is evident that plants are infected, they should be removed from the site and destroyed. An early, aggressive management approach has been shown to reduce amounts of disease later in the season.
Start an insecticide program as soon as seedlings emerge or immediately after transplanting. This is critical to protecting very small plants from beetle feeding and, ultimately, from bacterial wilt. Bactericides are not recommended for management of bacterial wilt disease. Plastic and reflective mulches, crop rotation have shown promising effect against the insects.
More information: http://plantpathology.ca.uky.edu/
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