- Author: Alireza Pourreza
UC Digital Agriculture Program's innovative spray backstop system reduces airborne pesticide drift by 78% in almond orchards– a big step forward for improving air quality and working conditions in California's agricultural production areas.
The Issue
Pesticide drift is a significant concern, especially in California's almond orchards. It's not just an environmental issue. Pesticide drift can pose a public health risk by contaminating the skin, lungs, and gut of people in nearby communities. These chemicals can lead to respiratory issues, skin irritation, and other adverse health effects. Another study highlights that pesticide poisoning is a significant cause of morbidity and mortality, affecting not just agricultural workers but also the general population.The challenge has been to control this drift without reducing the effectiveness of the pesticide application. This project aims to tackle this pressing issue head-on.
How UC Delivers
Addressing the issue of pesticide drift requires a multi-disciplinary approach, combining engineering, agriculture, and environmental science expertise. The UC Digital Agriculture Program team rose to the challenge by developing an innovative spray backstop system. This system is a blend of practicality and advanced technology, designed to be both farmer-friendly and effective in reducing pesticide drift.
The core components of this system are a foldable mast and a shade structure. The mast is the backbone, providing the necessary height and stability, while the shade structure acts as a barrier covering the trees from the top. This barrier is crucial in preventing the upward movement of pesticide droplets, thereby reducing the potential for drift.
Figure 1: Schematic design of the backstop prototype installed on a sprayer in an almond orchard.
To validate the effectiveness of this system, a series of tests were conducted in young almond orchards. The sprayer was operated at a 3.2 km/h speed to simulate real-world conditions. But before hitting the field, the team employed advanced uncrewed aerial systems equipped with thermal and RGB cameras. These cameras captured images and videos of the spray pattern from multiple angles, providing invaluable data for analysis.
The aerial imagery was not just for show; it played a pivotal role in the project. It allowed the team to monitor the spray application in real-time and understand the spray cloud's movement pattern. This imagery was then used to refine the design of the shade structure, ensuring it effectively blocked droplet movement beyond the treetop.
Figure 2: Aerial views showing the efficiency of the backstop prototype in blocking the spray cloud.
The results were more than just promising. The backstop system effectively blocked the spray cloud, ensuring that the pesticides stayed precisely where they were intended to be—on the trees. This was further validated through a ribbon test, a simple yet effective method to measure drift. A ribbon placed in the spray path remained in its resting position when the backstop system was used, indicating a significant reduction in drift.
The project didn't stop at just reducing drift; it also ensured that the reduction did not come at the cost of effectiveness. The on-target deposition of the pesticide was not compromised, affirming that the system could achieve dual objectives: reducing drift while maintaining efficacy.
The Impact
The spray backstop system's impact goes beyond just numbers. It represents a significant stride toward sustainable agriculture and community well-being. The system successfully reduced the drift potential by 78%. This isn't merely a statistic; it's a tangible change that has far-reaching implications for both environmental stewardship and human safety.
Figure 3: Statistical results showcasing a significant reduction in drift potential.
The environmental impact is equally noteworthy. Reduced drift means fewer chemicals in the air, contributing to "improved air quality," a UC ANR condition change. This is a step forward in reducing air pollution, which has wide-ranging implications for human health and climate change.
One of the most noteworthy aspects of this innovation is that it managed to reduce drift without compromising the effectiveness of the pesticide application. The on-target deposition remained consistent, ensuring the almond trees received the necessary pesticide coverage for optimal growth and yield. This is a crucial factor for farmers who are often caught in the dilemma of choosing between effective pest control and environmental responsibility.
Figure 4: Comparative leaf samples illustrating consistent on-target deposition and coverage.
The project aligns with another UC ANR's condition change, "improved living and working conditions for California's food system and farm workers." One of the goals of reducing pesticide drift is to mitigate the health risks associated with working and living in agricultural production areas. Therefore, the work directly supports UC ANR's commitment to promoting the public health of California's communities.
Looking ahead, the project has set the stage for further research and development to adapt the system for different types of orchards and terrains. Additional modifications are being considered to make the system even more robust and versatile, ensuring its long-term sustainability and broader applicability.
Want to learn more? See the method in action here.
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- Author: Brad Hanson
Its not too late to register for the San Joaquin Valley Spray Application Short Course (November 12-14).
Here's a link to the webpage: https://ucanr.edu/sites/SJVSprayApplication/Home/
Here's a link to the full agenda: https://ucanr.edu/sites/SJVSprayApplication/Agenda/
- Author: Lynn M. Sosnoskie
There are TWO upcoming weed science extension days in the San Joaquin Valley this April.
The first will be held on the 2nd of April at the Kearney Agricultural Research and Extension Center in Parlier (9240 South Riverbend Road, Parlier CA 93648) and the second will be held on April 11th at the Westside Research and Extension Center in Five Points (17353 West Oakland Avenue, Five Points, CA 93624).
The meeting at the Kearney Center will focus on rangeland, turf, and tree and vine systems while the meeting at the Westside Center will focus on agronomic crops, ROWs, and tree and vine systems. Both meetings will open with hands-on weed ID and nozzle selection/drift management training.
The Kearney meeting has been approved for 3.5 CDPR continuing education credits (other); an application for 3.5 credits is currently pending for the Five Points meeting.
Both meetings are free to attend although we do request that you register by calling the UCCE Merced County office at 209-385-7403 to reserve your spot. Agendas are listed below (pdf flyers are also attached).
Our programs are open to all potential participants. If you require special accommodations, please contact the UCCE Merced County office at 209-385-7403. Thank you and we hope to see you at the meeting!
San Joaquin Valley Weed Science Day at the KARE
Tuesday, April 2 2019, 8:00 a.m. – 12:15 p.m.
Kearney Agricultural Research and Extension Center
9240 South Riverbend Road, Parlier CA 93648
8:00 a.m. Registration and Welcome (Refreshments provided)
8:30 a.m. Concurrent Sessions (attendees will be split into two groups and will rotate between the weed ID and spray drift demonstrations at 45-minute intervals)
Session 1: Identification of Common Weeds of Agricultural Cropping Systems and Non-Crop areas of the Southern San Joaquin Valley.
Anil Shrestha, Chair: Department of Viticulture & Enology and Professor: Weed Science, CSU Fresno
Session 2: Nozzle Selection and Proper Use and Spray Drift Management
James Schaeffer, Staff Research Associate, UCCE – Fresno County
10:00 a.m. Break (Refreshments provided)
10:15 a.m. Post-Emergence Herbicides for Use in Orchards
Kurt Hembree, Weed Science Advisor, UCCE – Fresno County
10:45 a.m. Turfgrass Weeds in the Central Valley
Maggie Reiter, Environmental Horticulture Advisor, UCCE – Fresno, Madera, Tulare and Kings Counties
11:15 a.m. Post-fire Rangeland Weed Management: A Critical Component of Land Stewardship
Rebecca Ozeran, Livestock and Natural Resources Advisor, UCCE – Fresno and Madera Counties
11:45 a.m. Glyphosate for Weed Control: How it Works, Why it Fails, and What we can do to Maximize Efficacy
Lynn Sosnoskie, Agronomy and Weed Science Advisor, UCCE – Merced and Madera Counties
12:15 p.m. Adjourn
San Joaquin Valley Weed Science Day at the WSREC
Thursday, April 11, 2019, 8:00 a.m. – 12:15 p.m.
Westside Research and Extension Center
17353 West Oakland Avenue, Five Points, CA 93624
8:00 a.m. Registration and Welcome (Refreshments provided)
8:30 a.m. Concurrent Sessions (attendees will be split into two groups and will rotate between the weed ID and spray drift demonstrations at 45-minute intervals)
Session 1: Identification of Common Weeds of Agricultural Cropping Systems and Non-Crop areas of the Southern San Joaquin Valley.
Anil Shrestha, Chair: Department of Viticulture & Enology and Professor: Weed Science, CSU Fresno
Session 2: Nozzle Selection and Proper Use and Spray Drift Management
James Schaeffer, Staff Research Associate, UCCE – Fresno County
10:00 a.m. Break (Refreshments provided)
10:15 a.m. The Biology and Management of Alkaliweed
Kurt Hembree, Weed Science Advisor, UCCE – Fresno County
10:45 a.m. Managing tough weeds in the right-of-way (ROW), landscape and other non-crop sites
Rick Miller, Corteva Agrisciences
11:15 a.m. Pre- and Post-Herbicide Performance on Threespike Goosegrass in Tree Nut Orchards
Drew Wolter, UC Davis
11:45 a.m. Breaking Bindweed: What Controls the Species and What Doesn't Work
Lynn Sosnoskie, Agronomy and Weed Science Advisor, UCCE – Merced and Madera Counties
12:15 p.m. Adjourn
- Author: Brad Hanson
Glyphosate is one of the most widely used herbicides in the world and is extremely important in many of our orchard, vineyard, and annual crops as well as in non-crop and home situations. However, it can be confusing to understand some of the differences among various formulations of glyphosate herbicides.
I'll paraphrase a recurring extension question as “I'm trying to compare the rates and cost-effectiveness of two glyphosate herbicides. One lists the active ingredient as ‘41% glyphosate as the isopropylamine salt' and the other as 48.7% glyphosate as the potassium salt'. How do I compare these two herbicides?”
First important point, glyphosate is a weak acid herbicide. The various salt formulations have major impacts on how the herbicide behaves in the jug, and to some degree on how it gets into the plant. But once in the plant, it is the glyphosate acid that binds to the target enzyme in susceptible plants and causes the herbicidal effect.
What is a salt? From a chemistry perspective, a salt is simply a compound formed by ionic bonding of two ions of opposite charge. Glyphosate acid has a weak negative charge and the salt is formed when the glyphosate acid is bound to a base that has a positive charge. In the cartoon below, this is illustrated a little incorrectly - you can see the negatively charged glyphosate acid on the left (C3H8NO5P); however, the "salt+" tagged on the right should really be labeled "base+" (the combined molecule is actually the "salt").
What are some common glyphosate salts? There are several glyphosate salts currently available in the market and others have been in the past but are less common now. Four examples (below) include: isopropylamine, dimethalamine, trimesium, and potassium salts. (images mostly lifted and modified from www.chemsrc.com).
In case it's been a while since your last organic chemistry class, here's a quick refresher on nomenclature. In the isopropylamine salt, that simply means it as a 3-carbon chain (that's “propyl”) and amine group (NH), and the chain is connected in the middle (the “iso” position) rather than on one end. Dimethylamine indicates two (di) methyl groups and an amine. Trimesium is a shortened name for trimethylsulfonium which means three methyl groups and a sulfur. Potassium means, well that one's pretty straightforward and means potassium (K).
How does the salt formulation affect the herbicide? The salt formulations are those of us managing weeds for a couple of important reasons.
- First, the different glyphosate salts have different solubility in water (or other solutions). This doesn't have much, if any, effect when we have the herbicide diluted in water to make a spray application (eg. quarts of product in 10 or more gallons of water). However, it has a big impact on how concentrated the herbicide can be in the formulated product. (It's useful here to note that pure glyphosate is actually a solid crystal that is dissolved in liquid to make the products we use in the field.) In the example I started with, that is the big driver behind why one product has 41% active ingredient and the other has 48.7%. From a packaging, shipping, storing, and handling perspective, it's far more efficient to have more concentrated materials (eg less water). So, we can assume the potassium salt is quite a bit more soluble than the isopropylamine salt form of this herbicide.
- Second, the different glyphosate salts have different weights. Remember the periodic table of the elements? The atoms that make up the salts (and any other chemical structure for that matter) have markedly different weights on an atomic scale. For our purposes, we can think of this as a carbon (C, atomic number 6) weighing six times a hydrogen atom (H, atomic number 1) and a potassium (K, atomic number 19) weighs about three times what carbon does. Of course, the glyphosate acid weight is the same C3H8NO5P in each formulation – only the salt is different. So, it is important to remember that in these herbicides the “active ingredient” (AI) is the salt formulation (eg glyphosate isopropylamine) and that each of the different active ingredients has a slightly different weight.
How can I use the percent active ingredient to compare products? I'll be honest here, I find it very confusing to think about the percent AI list on the label of a glyphosate herbicide. As I indicated above, this does not allow a straight across comparison for two different salts (eg a potassium salt glyphosate is not the same weight as a dimethylamine salt). More importantly, the percentage listed on the label is actually on a weight basis (weight of glyphosate salt per weight of formulated herbicide). I don't know about any of you, but I typically measure glyphosate herbicides by volume (fluid ounces, quarts, milliliters) rather than by weight (ounces, pounds, kilos). So knowing the amount of glyphosate per pound of Roundup Powermax isn't very helpful to me when I don't weigh the liquid.
Instead of focusing on the percent active ingredient, look on the label just below where the percentages are listed for the active ingredient and acid equivalent information. (I'm looking at a Roundup PowerMax label and a Credit41 label, but there are dozens of examples).
In these two herbicides, you can see:
- Credit41 has 4 lbs per gallon of glyphosate as the isopropylamine salt, which is equivalent to 3 lbs per gallon of glyphosate acid.
- Roundup PowerMax has 5.5 lbs per gallon of the glyphosate potassium salt, which equates to 4.5 lb/gal of the acid.
So, once we're comparing on an acid equivalent (AE) basis, we can see that that one product is 50% more concentrated than the other (3 lbs vs 4.5 lb ae). If you wanted to make an equivalent rate (AE per acre) you'd have to apply 50% more of the 3 lb product to have the same amount of glyphosate acid. Similarly, in making cost comparisons, you should be thinking about it in terms of cost per unit of glyphosate acid. In the above example, if making an equivalent AE rate per acres, the breakeven point would be if the 3 lb material costs 2/3 of what the 4.5 lb material costs. Don't make the mistake of assuming a quart of one glyphosate is the same as another (or that a 2% solution of two different products is equivalent!
Check out this publication we did a couple years ago On the second page, there's a chart that illustrates this concept – if you wanted to apply a rate of ¾ lb ae per acre, you'd need to apply 32 fl oz of a 3.0 lb ae/gal material (eg Credit41, Roundup Original) but only 22 fl oz of a 4.5 lb ae/gal material (eg Roundup PowerMax).
What else is different among the formulations? This is a really good question without a really clear answer.
Besides the glyphosate-salt that makes up the active ingredient in each formulation, there are other components of the herbicide product. Some of these influence physical properties that affect handling, storage stability, etc. Others are surfactants and other adjuvants that impact how the herbicide penetrates the leaf surface. The surfactants (types and loading) are proprietary information and are not reported in the same way as the active components are so this can be difficult to ascertain. However, one way that price points can be reduced in this competitive market (lots of generic glyphosate herbicide due to loss of patent protection) is to reduce or change the surfactant packages. Thus, even if the active ingredient is the same between two products, they could have substantially different surfactant loading which can impact weed control efficacy (amount of herbicide getting to the target enzyme in the plants). If you use a low-surfactant-load glyphosate product, you should consider adding appropriate surfactants to make up for it.
I'll wrap this up by saying that I think a weed manager can get similar levels of weed control performance with the wide range of glyphosate herbicides currently available on the market. However, it is really important to make sure you're comparing apples-to-apples in determining rates needed from the various salt formulations and concentrated products. In my experience, at equivalent AE rates, a 3 lb glyphosate plus a good surfactant can perform similarly to a higher AE and higher surfactant load formulations; however, be sure to sharpen your pencils to make sure the savings from the cheaper AI isn't offset by higher required rates and surfactant additions.
12/21/17 - lightly edited to clarify that the "salt" is the combined molecule that includes the glyphosate acid and the "base" (it's been a while since my last O-chem class too!). BH
- Posted by: Gale Perez
The Western IPM Center's May 2017 newsletter just came out.
The IPM VIDEO OF THE MONTH is on a robotic herbicide sprayer that targets weeds.