- Author: Whitney B Brim-Deforest
- Author: Roberta Firoved
- Posted by: Gale Perez
Dates for the training are posted on the California Rice Commission calendar https://calricenews.org/events/, as well as the UC Rice website.
Controlled weeds are sprangletop, ricefield bulrush, and smallflower umbrella sedge. The application timing begins from day of seeding up to 82 days before harvest. Recommended timing for sedges is pre-emergent up to the 5-leaf stage, and for sprangletop, pre-emergent up to the 2.5 leaf stage as well as at tillering.
Flood water should be a minimum of 4 inches when the product is applied. The active ingredient, benzobicyclon, is a proherbicide, meaning that it is not active until it comes into contact with water. Therefore, for maximum efficacy, water should be held in the field for at least 5 days. Longer periods of flooding will result in better efficacy, whereas a drain soon after application will both reduce efficacy as well as encourage a new flush of weeds. The recommended waterhold is 10-14 days for maximum efficacy.
Cliffhanger™ should only be applied once per season. It is not recommended that it be applied in the same season as any other HPPD-inhibitor product (Butte®). Applying both in the same season can select for herbicide resistance and may cause significant phytotoxicity to the rice. Repeated applications, both during the same season, or season after season, can select for resistance, particularly in sprangletop, ricefield bulrush, and smallflower umbrella sedge.
Remember to always follow all label instructions when applying any pesticide, as the label is the law. Make sure to pay particular attention to the Use Precautions and Restrictions. Consult your local Agricultural Commissioner's Office regarding buffer zones and aerial restrictions, before making any applications.
Label and SDS: https://www.gowanco.com/products/cliffhanger-sc-herbicide
Original source: Rice Notes - January 2024 newsletter
- Author: Aaron Becerra-Alvarez
- Author: Sarah Lorraine Marsh
- Author: Kassim Al-Khatib
- Posted by: Gale Perez
A new herbicide for early-season weed control in water-seeded rice will be available soon. The herbicide active ingredient (a.i.) is pyraclonil, which will be trademarked as Zembu™ (1.8% a.i.) by Nichino, America Inc. The mode of action is a protox porphyrinogen (PPO)-inhibitor or Group 14. This herbicide is formulated as a granule and will be used as a residual preemergence for application on the day of seeding onto flooded fields. The use rate is 14.9 lbs ac-1 applied by air. While this herbicide is not a new mode of action for water-seeded rice, it is a new mode of action for early-season residual weed control. Pyraclonil is widely used for weed control in paddy fields worldwide and is the most commonly utilized herbicide in Japan [1]; however, Zembu™ will be the debut of pyraclonil to the U.S. rice market [2].
In order to evaluate Zembu's strengths and weaknesses, UC researchers, in collaboration with Nichino, America, has conducted extensive research on Zembu since 2015 and developed foundational information for the use of Zembu in California water-seeded rice. In this post we highlight two studies which demonstrate Zembu's use and how it can be incorporated in an herbicide program for season-long weed control.
Zembu Timing
In the study conducted at the Rice Experiment Station in Biggs, CA in 2019, 2020 and 2023, Zembu application timings were evaluated. The pre-seed bare ground was the first Zembu application at 3 days before flooding the field and seeding rice, then the application at 1-inch flood, then the application at 4-inch flood, followed by the application 3 days after flooding (DAF). The rice was seeded after the 1-inch flood and before the 4-inch flood. 'M-209' rice was seeded in 2019 and 2020 at 120 lbs ac-1 and 'M-209' was seeded in 2023 at 150 lbs ac-1. The objective of studying the different application timings was to determine if the application timing will affect weed control and rice response.
Cross species weed control was not affected by the different application timings of Zembu (Table 1). Zembu does not have great activity on ricefield bulrush and changing the application timing did not improve its control, which reached only 60% by 42 days after treatment (DAT) (Table 1). Zembu provided excellent control of smallflower umbrella sedge and all present broadleaves, which included ducksalad, water hyssop and redstem (Table 1). Across years, there were differences in control levels for watergrass control; however, there were no observed differences in watergrass control across the application timings (Table 2). In 2020, where watergrass control levels were low, was a year when the whole field had an increased pressure of watergrass caused by late rains immediately before the field preparation and initial flood, which provided soil moisture to give the grasses a head start. In 2019 and 2023, all weeds and rice germinations were initiated at time of flooding and led to greater control of watergrass (Table 2). The Zembu label will note that watergrass is suppressed by the chemical, not controlled. When applicators use Zembu for herbicide control, the incorporation of other herbicides to control ricefield bulrush and watergrass populations will be important.
Zembu in Herbicide Programs
Zembu will need to be incorporated into herbicide programs for season-long control. In the study conducted in 2019 and 2021 at the Rice Experiment Station in Biggs, CA, herbicide programs that included Zembu were evaluated for weed control and rice response. ‘M-206' rice was seeded at 120 lbs ac-1 and 150 lbs ac-1 in 2019 and 2021, respectively. All Zembu applications were done at day of seeding (DOS) onto the 4-inch flood. All other herbicides were applied following their label (Table 3).
When accompanied and followed by other herbicides, Zembu is a great addition to achieve season-long weed control (Table 3). In this study, it is observed that Zembu alone did not control the watergrass and when followed by various other herbicides the control level was increased (Table 3). Similar with ricefield bulrush control, other herbicide combinations increased the control levels when compared to Zembu applied alone (Table 3).
Rice response was minimal across treatments except with the Zembu and Bolero Ultramax combinations, which demonstrated greater visual injury early on. However, injury was overcome later in the season and rice grain yield did not differ across treatments (Figure 1).
Zembu will be a great addition to the herbicides available for early-season weed control in water-seeded rice.
References
[1]. Zhang YB (2014) Development and application of pyraclonil in paddy field. World Pestic 36(6):1-3
[2]. Anonymous (2023) Zembu™ Herbicide. Nichino America, Inc. Accessed on January 14, 2024 from https://nichino.net/products/zembu-herbicide/
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- Contributor: Drew Lyon
- Posted by: Gale Perez
Over the past two years (2022 and 2023), we conducted field studies to evaluate the benefits of using herbicides with different modes of action, both with and without glyphosate, for the control of Italian ryegrass in glyphosate-resistant spring canola. We found that glyphosate (Roundup PowerMax) provided excellent control of Italian ryegrass applied alone or in combination with other herbicides. The use of trifluralin (Treflan HFP) applied preplant incorporated or the early postemergence application of glufosinate (Liberty) reduced the number of Italian ryegrass plants that were subsequently treated with glyphosate. The fewer plants you treat with glyphosate or any other herbicide, the lower the chance for selecting an individual or individuals with resistance to glyphosate. Consequently, the use of trifluralin or glufosinate for weed control in glyphosate-resistant spring canola can potentially extend the useful life of glyphosate-resistant spring canola for Italian ryegrass control.
Despite the good news on weed control, we observed a yield reduction with some of the glyphosate applications in both years. In 2022, the greatest Italian ryegrass control resulted from applications of Roundup PowerMax, which provided nearly 100% control at harvest (Table 1). Applications of Roundup PowerMax were so effective in controlling Italian ryegrass that it was difficult to see added control from Treflan HFP. The early Roundup PowerMax application (3-4 leaves) of 44 oz/A resulted in the highest canola yield of 2590 lb/A. All late postemergence Roundup PowerMax applications (6-leaf to bolting) delayed flowering and reduced yield.
In 2023, a year with a low density of Italian ryegrass (the result of a delayed replanting), all treatments except Liberty applied alone early postemergence provided excellent control of Italian ryegrass (Table 2). Without the competition provided by a high density of Italian ryegrass, we were able to observe a reduction in canola yield with all treatments containing Roundup PowerMax. It did not matter if the Roundup PowerMax was applied early or late postemergence or at a rate of 22 or 44 oz/A. We are unsure if this is a problem unique to the TruFlex spring canola varieties we used (Invigor LR344PC and Invigor LR345PC) or if it should be a concern for all Roundup Ready spring canola varieties. Further research is needed to better understand the yield drag associated with the use of glyphosate in Roundup Ready spring canola.
In the meantime, growers should be aware of this potential yield drag in glyphosate-resistant spring canola. The yield drag appears to be partially the result of a delay in plant development and flowering. This delay often results in increased heat and drought stress during flowering, which reduces yield. Growers are encouraged to avoid late planting of glyphosate-resistant canola varieties; however, if late planting is necessary, growers should consider not applying glyphosate and possibly further delaying crop maturity. Late planting may allow control of major Italian ryegrass flushes before planting, thus reducing in-crop infestations. Growers are encouraged to consider the use of a preplant herbicide such as trifluralin or ethalfluralin (Sonalan HFP) prior to an early postemergence application of glyphosate to reduce selection pressure for glyphosate-resistant Italian ryegrass biotypes.
Drew Lyon is an Endowed Chair and Professor in the Department of Crop and Soil Sciences at the Washington State University.
Original source: Weeders of the West blog :: Nov. 22, 2023
- Author: Mick Canevari
- Author: Brent A Holtz
- Posted by: Gale Perez
The 2023 post-harvest season is upon us and it's time to prep for your fall/winter weed control activities. The long-range forecast is calling for another wet winter, and November is the ideal time to plan your early winter weed control program, to check that your spray equipment is functioning properly and calibrated, and to clean your orchard floor of nuts and debris.
There are a variety of herbicides available today for our tree and vine production systems. No one herbicide will control all the weeds present, but choices exist to achieve excellent control for almost every weed combination. However, it takes patience and persistence to win the weed war. Before programs are decided, the following key questions should be discussed with your pest control adviser (PCA). Tree age, root stock, soil composition (sand, clay, gravel), irrigation design and practices, water source and quality, cultural practices used, a list of weed species present, and whether they are annual, biennial, or perennial weeds, your spray nozzle design, spray volume required, and if there are sensitive crops nearby. Discussing these questions early will provide the basis for your PCA to make the best recommendations possible while allowing your applicator to minimize the risk of crop injury or drift issues.
Advantages of early weed control
The advantage of implementing an early pre-emergent herbicide program, “before leaf fall occurs” is to get a jump start on winter germinating weeds at a time when they are just emerging and susceptible. Applying a pre-emergent ahead of a rain, or by activating with sprinklers, will control millions of weed seeds and provide a clean tree row for 4-6 months into spring. Applying a pre-emergent ahead of leaf drop also eliminates an additional operation of sweeping or blowing leaves after leaf drop has occurred. Weed control is enhanced and herbicide efficacy is extended when the herbicide is already in place before leaves cover the soil. A leaf barrier after an application inhibits weed germination and improves herbicide efficacy. As more orchards and vineyards turn to drip irrigation, relying on rain events to set herbicides becomes critical. A weed management program applying soil active herbicides early in the fall (November/December), and repeated in spring while rain events are still forth coming (March/May), will provide good weed control into summer. Orchards with sprinkler irrigation have more flexibility in timing their applications and selecting herbicides.
Pre-emergent herbicide use is also a recognized strategy to manage herbicide resistant weeds that have become established. We hear complaints every year that post-emergent herbicides are failing to control the same weeds they used to; and that higher application rates are needed to achieve the same level of control. Some of our more frequently used herbicides are developing weed resistance in the field: they include; glyphosate, paraquat, sethoxyodim, clethodim, rimsulfuron and other related acetolactate synthase (ALS) inhibiting herbicides.
Herbicide resistant weeds continue to spread across the state in different cropping systems, with the greatest occurrence in perennial orchards and vineyards. Problematic weeds include annual ryegrass, junglerice, goose grass, hairy fleabane, palmer's amaranth and horseweed or marestail with several other annual weeds close behind in developing resistance. There are several approaches to control these resistant weed species--but the best option by far is starting with a pre-emergent herbicide program early and attacking weed seeds at the point of germination.
New herbicides expected in 2023-2024
We are always anxious to share information from our various weed and herbicide research trials. But we never know for certain when a new herbicide will be registered for use in California. Two new herbicides are expected to be available this coming season, Florpyrauxifen-benzyl and a combination product with Indaziflam and Rimsulfuron.
Hulk (florpyrauxifen-benzyl) is a post emergent synthetic auxin mode of action HRAC (herbicide resistance action committee) group 4 herbicide from Corteva Agriscience. It is a foliar uptake and systemic herbicide that translocates through the phloem and xylem accumulating in meristematic tissue. It exhibits herbicidal symptoms of twisting and epinasty, typical of phenoxy herbicides. It targets many broadleaf weeds, typical of phenoxy herbicides, but with greater efficacy with certain weed species. Symptoms develop rapidly when plants are actively growing, but whole plant death may take several weeks to a month depending on the growth stage and environmental conditions. Currently, labeled crops include pome, stone, citrus and tree nuts. Grapes are being explored and may be added to the label in 2025. Tank mix partners are needed for emerged grasses which may include the use of glufosinate, glyphosate, clethodim and some ALS herbicides with post grass activity. Generally, one should avoid using contact herbicides that readily burn leaf tissue, like “paraquat” for example, since they may inhibit foliar absorption and systemic movement needed to control the weed. Check the label for specific recommendations.
Centrus (Indaziflam + Rimsulfuron) is a pre-emergent herbicide from Helena Agri company packaged with two active ingredients and modes of action herbicides in HRAC group 29 & 2. Centrus will provide long term pre-emergence control over a broader spectrum of weeds and grasses. It is labeled for tree fruit, nut, and vines for residual weed control targeting winter and summer annual weeds common in orchard and vineyards, including annual ryegrass, filarees, fleabane-horseweed, malva, shepherd's purse, willowweed, knotweed, and many more. In all cases it will be necessary to add a post emergent herbicide for emerged weeds. By combining two active ingredients with different mode of actions, it broadens weed control across more species while slowing herbicide resistance to either active ingredient. We need to be mindful of mixing different modes of action herbicides and not using the same herbicides repeatedly. By mixing different mode of action herbicides we strive to keep our products viable for years to come.
Overview of pre-emergent (before weed germination) herbicides currently registered
Craze (orthosulfamuron) HRAC Group 2 is a new 2022 broad-spectrum soil residual herbicide from Nichino America. The active ingredient in CRAZE is orthosulfamuron. This herbicide, an acetolactate synthase (ALS) inhibitor, works by inhibiting the enzyme responsible for the production of amino acids (valine, leucine, and isoleucine) essential for plant growth. CRAZE has demonstrated broad spectrum residual control of many broadleaf and grassy weeds including horseweed and fleabane and suppression of yellow nutsedge if applied in a timely pre-emergent manner. Several years of testing has demonstrated that it will fit into our Tree and Vine weed control program with flexibility and safety. In our testing, it included tank mix combinations with Alion, Chateau and Prowl which extended long-term control.
Prowl H2O and Surflan (pendimethalin & Oryzalin) are HRAC group 3 herbicides that have excellent annual grass control along with many broadleaves, especially those that germinate in the spring and summer. Surflan and Prowl are of the same mode of action and are similar in their weed spectrum and residual properties. Prowl H2O and Surflan remain stable on the soil without moisture no more than 21 days. Prowl is in the DNA family which controls weed seeds once the germination begins by inhibiting meristematic growth and plant cell division or mitosis, inhibiting seedling development. A common weed control strategy in the fall is to use a mode of action herbicide such as Chateau, Matrix, Alion, Pindar GT, Craze, and then switch to the DNA chemistry of Prowl/Surflan in the late winter or spring timing (February to May) to control summer annual broadleaf weeds and grasses. Prowl is an herbicide used for newly planted orchards because of its strong affinity of soil binding properties and safety to young trees. Prowl may be used before or after transplanting nonbearing nut and fruit crops and roots are covered with at least 2 inches of soil. Always follow the label instructions.
Chateau EZ (flumioxazin) is now in a new liquid formulation. Fortunately, the use rates and product rates for the new formulation remain the same, so the conversion from granular to liquid also remain the same. It is HRAC group 14, a long-lasting pre-emergent herbicide used for tree, nut, and vine crops. Applied between 8 -12 ounces per treated acre, Chateau enhances burndown of small broadleaf weeds and provides long residual control of difficult to control weeds such as fleabane and horseweed (marestail), malva, willow weed, filaree and a host of other winter weeds. Its broad-spectrum control of winter annuals makes it an excellent herbicide for use in the fall and early winter timing during the dormant period. Chateau at lower rates (6-8 ounces) has become a popular tank mix with other pre-emergent herbicides to extend control of more grass species and slow herbicide resistant issues. New Plantings: Chateau EZ provides early protection of new plantings from weeds. It can be applied immediately after planting according to label guidelines. Trunk protectors are required.
Matrix (rimsulfuron) HRAC group 2 is an ALS inhibitor pre-emergent herbicide active on many winter and summer weeds including fleabane, willow weed, and marestail, barnyard grass, jungle rice, crabgrass. Its broad-spectrum activity on grasses and broadleaf weeds, make it a good fit for an early fall application timing in November or December. It has become a popular herbicide to manage glyphosate resistant ryegrass pre-emergent and is effective post emergent on small emerged ryegrass. We have observed nice broad spectrum weed control when other pre-emergent herbicides are combined with Matrix. A post emergent herbicide should be added when weeds are emerged. Matrix is safe on young trees and a popular tank mix with Prowl or Trellis.
Mission (Flazasulfuron) is a HRAC group 2, an ALS inhibitor in the same family as rimsulfuron, orthosulfamuron (Matrix, Craze) with a similar weed spectrum. Our research has shown that Mission increased post emergent activity on certain weeds at a rate of 2.14 ounces per acre. Research from other Farm Advisors suggests improved yellow nutsedge activity when applied ahead of emergence with adequate water for soil incorporation. Use a post herbicide as a tank mix partner when weeds are up.
Alion (indaziflam) is a broad spectrum pre-emergent soil active herbicide registered in tree nuts and vines. It is a long-lasting soil residual herbicide exceptional in controlling many grasses and broadleaf weeds. It is effective on both winter and summer annual weeds, including fleabane, marestail, sowthistle, and willow weed, shepherd's purse, chickweed, and most grasses. At least 1/4 inch of water is needed to set and activate Alion as a soil residual. Since it is strictly a pre-emergent herbicide, it requires a tank mix with a post herbicide for emerged weeds, typically Rely, Matrix, Shark, Goal, Roundup, Venue, Treevix and Gramoxone are all compatible. Alion has shown to be an excellent tank mix partner with other pre-emergent herbicides to increase its weed spectrum, especially for malva and knotweed. Since it does not control weeds already germinated or just under the soil surface (called white phase) it should be tank mixed with herbicides that will control weeds just prior to emerging (Matrix, Mission, Pindar Gt or Goal are some popular choices).
Pindar GT (oxyfluorfen and penoxsulam) HRAC group 14 & 2 is a premix with two active ingredient herbicides. It combines both a pre- and post-emergence punch for many broadleaf weeds used in tree nuts and fruits but not registered in vineyards. An excellent herbicide for winter applications beginning in November to January, that can provide residual control lasting into spring and early summer. It is especially effective on fillaree, malva, henbit, willow weed, sowthistle, fleabane and marestail among others. If weeds have emerged, it is still recommended to combine it with a post emergent herbicide such as Roundup, Rely, or Gramoxone. If heavy grass pressure is anticipated in the orchard, an addition of Prowl, Matrix or Alion will extend long term grass control into spring. Within 14 days of application, a half-inch of water is needed to set and activate the herbicide.
Trellis (isoxaben) HRAC group 21 is registered for use in tree nut and fruit crops and for non- bearing newly planted orchards (check label for specific timing). It is a pre-emergent herbicide controlling only broadleaf weeds, therefore consider using another herbicide for grass control. Applied in the fall and winter timeframe, Trellis will provide 4-5 months of broadleaf control. It has no post-emergent activity; therefore, it must be tank mixed with the commonly used post emergent herbicides Trellis' mode of action is unique; it inhibits cellulose development making it a good rotational herbicide to manage weed resistance. If grass weeds are an issue, the addition of herbicides with grass control activity such as Prowl, Matrix, Alion, or Surflan are needed.
Broadworks (mesotrione) HRAC group 27 is registered in almond, walnut, pistachio and certain fruit crops. It is primarily a pre-emergent herbicide to control only broadleaf weeds hence the name Broadworks. We have observed some post activity on small broadleaf weeds (fleabane marsetail) when actively growing but to be safe will still require a post emergent herbicide partner for complete burn down control. Broadworks controls some of the more difficult broadleaf weeds in orchards but will need a pre-emergent tank mix partner that controls germinating grasses. We have observed a general reduction in bindweed populations when spring applications of Broadworks are used ahead of emergence.
Goal (oxyfluorfen)HRAC group 14 is a PPO (Protoporphyrinogen oxidase) post-emergent broadleaf herbicide with a soil residual of 1-3 months depending on the rate. Goal has been a mainstay in broadleaf weed control for decades and is especially useful in our fall orchard and vineyard programs as a burn down of broadleaves. It is regulated for application use due to its co-distillation (lift off in warm temperatures) issues subject to drift. Goal Tender is a different formulation of oxyfluorfen which reduces volatility issues associated with the 2XL formulation. Under our fall/winter conditions and weed species Goal is very good on malva, burning nettle, henbit, sowthistle, prickly lettuce and many more broadleaf annuals. It is weak on grass species and does miss some broadleafs as well. We encourage tank mixes with other pre-emergent herbicides of different HRAC groups for extending soil residual control.
Post-emergent herbicides (when weeds are up)
Embed Extra (2,4-D) HRAC group 4 post-emergent herbicide is registered on almonds, pistachios, walnuts, pecans and certain tree fruit. It controls a long list of broadleaf weeds, both winter and summer annuals, and broadleaf biennials and perennials including marestail, bindweed, fleabane and malva. Embed Extra is a new post-emergent phenoxy herbicide, containing choline formulation of the active ingredient 2,4-D which reduces the risk of volatility (soil lift off) while minimizing drift. The systemic action of Embed Extra provides a more thorough kill down to the roots of larger broadleaf weeds, that many contact herbicides struggle with. Embed Extra translocates at a slower pace in weeds than contact herbicides. A grower won't see immediate visible burn, since its mode of action is systemic, mimicking the action of the plant growth hormone affecting cell division and slowly twisting until dead. Embed Extra can be tank mixed with other post-emergent herbicides, such as glyphosate and glufosinate. It can also be tank mixed with many “residual”-type herbicides.” Our trials on spring treated larger plants of fleabane, marestail and willow weed showed excellent results.
Rely (glufosinate ammonium) a HRAC group 10 herbicide has become a mainstay for growers needing a broad spectrum burn down herbicide to control tough broadleaf weeds and grasses; willowweed, barnyardgrass, junglerice, crabgrass and glyphosate resistant fleabane and marestail. In recent years, the development and spread of glyphosate resistant weeds has shifted our growers to use more glufosinate herbicide in combination with other post emergent herbicides. Rely does not translocate totally like glyphosate, so the key to success is good coverage and smaller weed size. It is a popular tank mix with any of the pre-emergent herbicides. We have found that glufosinate plus other foliar herbicide combination to be very effective across most emerged weeds.
Treevix (saflufenacil) HRAC group 14 is a PPO (Protoporphyrinogen oxidase) post-emergent broadleaf herbicide with a short soil residual of approximately 30 days. It is registered in tree nut and fruit crops. It is recognized as an excellent post emergent herbicide for some of our toughest emerged broadleaf weeds. However, it is mostly effective on broadleaf weeds, and should be mixed with another herbicide to control emerged grasses. Like all post contact herbicides, treating small weeds, 1-6 inches tall and using a 20-40 gallon per acre (GPA) rate and thorough spray coverage is important. Treevix is excellent in controlling young fleabane, marestail, malva, willowweed, sowthistle, nettle, henbit, prickly lettuce, especially in cool conditions from fall through spring. It is not considered a long soil residual herbicide, so it should be mixed with a pre-emergent herbicide for soil residual control.
Shark, Venue (carfenthrazone, pyraflufen ethyl)are group 14 PPO herbicides. They are all post emergent herbicides especially effective on broadleaf weeds having little soil residual. Theyprovide a tank mix addition to pre-emergent herbicides to control emerged broadleaf weeds. They also work well with other post herbicides glyphosate and glufosinate (Roundup and Rely). A rule for these and all post-emergent herbicides, "Spray when weeds are small for better coverage and control!"
Roundup, Rely, Gramoxone, 2,4-D & PPO (group 14 herbicides) are registered for multiple use in nut and fruit orchards year around. Growers having certain weed species may need multiple post-emergent treatments for specific weed issues or escapes. Glyphosate is moderately effective on purple nutsedge with repeated applications prior to the six-leaf growth stage. Yellow nutsedge can be controlled by using 3-4 quarts per acre of glyphosate at two sequential application timings. Sandia has shown very good results to control emerged nutsedge but is not registered on almond. Sandia is registered for use in pistachio and walnut orchards. The key to nutsedge and other perennial weeds is persistence with repeated applications as it emerges and before it can regenerate new underground nutlets or rhizomes. Problem broadleaves such as fleabane, horseweed, malva, knotweed that germinate most of the year, should be targeted early at a small growth stage and controlled before seed heads develop. Vigilance and persistence are necessary until orchards mature and reach a full canopy of shade to slow perennials and other weeds from continuous germination.
NOTE: Before using any herbicide, always check the label for any use restrictions applicable to your area, crop, or soil type. Our comments and suggestions are from years of testing herbicides in our research plots and field trials. We appreciate our grower cooperators, who let us have access to their orchards. Again, always review and follow label instructions.
Originial source: November 2023 Field Notes newsletter
- Author: Trina Kleist
- Posted by: Gale Perez
A contraption with a long, low, green metal arm swept noisily along the edge of a row of almond trees in an experimental orchard just west of UC Davis. Little flashes of light sparked between the bottom of the arm and the green weeds below, and puffs of gray smoke wafted up from the stricken pests.
Electrical energy zooms through the plant down into the roots, and the heat damages cells. “We start seeing injury in the weeds within 30 to 60 minutes after the treatment,” said doctoral student Tong Zhen, of the Department of Plant Sciences. “Most weeds will be killed in a day.”
Two weeks after treatment during an orchard trial in May, all of the treated hairy fleabane was dead, and 70 percent of the field bindweed was toast.
In addition to evaluating the effectiveness of this electrical weed control device, the multistate team also is evaluating its effects on crop safety and on the tiny organisms living in the soil. “Maintaining soil health is an important goal of most organic producers,” Zhen added.
The weed-zapper was demonstrated during the 2023 Weed Day held June 21, and it's the focus of research by Tong, staff research associate Seth Watkins and principal investigator Brad Hanson, all in the Department of Plant Sciences. In addition to studying the zapper's effectiveness, they are looking at soil health and crop safety after repeated uses in both almond and blueberry fields that are managed organically. Colleagues at Oregon State University are testing the device in cherry orchards, and colleagues at Cornell University are testing it in apple orchards.
Machines with vision, herbicide tests and Google Street View
More research presented during Weed Day included:
- Efficacy and crop safety of fluridone in pomegranates. Postdoctoral scholar Rohith Vulchi and Brad Hanson, a professor of Cooperative Extension.
- Effect of endothall-treated irrigation water on almond orchards. Stephen Chang, master's degree student, and Brad Hanson.
- Machine-vision cultivators in processing tomato. Steve Fennimore, professor of Cooperative Extension in the department, and Scott Stoddard, UCCE Farm Advisor.
- Farm machinery sanitation to reduce the spread of broomrape seed. Postdoctoral scholar Pershang Hosseini and Brad Hanson.
- Chemigation strategies to manage broomrape in processing tomatoes. Doctoral student Matt Fatino and Brad Hanson.
- Orchard crop injury from simulated rice herbicide drift. Doctoral student Deniz Inci, Brad Hanson and Kassim Al-Khatib, the Melvin D. Androus Endowed Professor for Weed Science.
More research:
- Weed control efficacy and crop safety of the PPO-inhibiting herbicide tiafenacil in orchards. Recent master's degree graduate Guelta Laguerre and Brad Hanson.
- Using Google Street View to map weeds along road networks, making weed control more efficient. Mohsen Mesgaran, an assistant professor in the department, Tong Zhen and Kassim Al-Khatib.
- Using pendimethalin for water-seeded rice. Doctoral student Aaron Becerra-Alvarez and Kassim Al-Khatib.
- Evaluation of group 15 herbicides in tree nuts. Recent master's degree graduate Andres Contreras and Brad Hanson.
Learn more methods at Weed Science School 2023
An intensive, hands-on course offered Sept. 19-21 teaches how to identify weeds, apply herbicides safely and detect symptoms of herbicide problems. Lectures and discussions will cover weed biology, ecology, organic weed management, herbicide action and resistance management, resistance prevention and environmental impacts.
The school is designed for those involved in consulting, research, development or sales of agricultural chemicals in the private or public sector. It's offered through the University of California Weed Research and Information Center.
More about Weed Science School 2023 here.
Find schedule, cost and a full agenda here.
Related links
More about Tong Zhen's evaluation of the electrical weed control device is here.
UC Weed Research and Information Center has lots of resources for weed management.
Agenda for Weed Day 2023, listing additional research.
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Original source: UC Davis • Dept. of Plant Sciences website • News: Sept. 5, 2023
Trina Kleist is the Communications Specialist for the Dept. of Plant Sciences at UC Davis. Her contact information is tkleist@ucdavis.edu, (530) 754-6148 or (530) 601-6846.