Jul 26, 2023Trends in Insect Losses and Management on Desert LettuceTo contact John Palumbo go to: jpalumbo@ag.Arizona.edu
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.
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
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/
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
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