- Author: Michelle Leinfelder-Miles
From 2019-2021, we conducted trials to evaluate the efficacy of a new herbicide product called Loyant (florpyrauxifen-benzyl; group 4 herbicide; Corteva Agriscience) in Delta drill-seeded rice. Loyant is registered in rice growing states in the southern US but would be a new chemistry in California. Previous work by the company indicates that Loyant provides good control of broadleaf weeds (e.g. ducksalad, redstems), smallflower umbrella sedge, and ricefield bulrush. Results from 2019 and 2020 Delta trials indicate that Loyant has efficacy on grass weeds in the drill-seeded system, like watergrass and barnyardgrass (Echinochloa spp.). The objective of the 2021 trial was to assess the efficacy of Loyant on yellow nutsedge (Cyperus esculentus) (Figure 1).
Figure 1. The most prevalent weeds in the 2019 and 2020 trials were A) watergrass and barnyard grass (Echinochloa spp.) and B) sprangletop (Leptochloa fusca). The most prevalent weed in the 2021 trial was C) yellow nutsedge (Cyperus esculentus). (Photos A and C by M. Leinfelder-Miles. Photo B courtesy UC IPM)
Please see the full report for trial methods, including treatment list and rates, and complete results with discussion. In 2021, we observed minor crop injury with all treatments in the form of leaf tip burning, but symptoms were no longer visible two weeks after treatment. No other injury symptoms were observed. In terms of weed control, the best treatment for yellow nutsedge in this trial was the grower standard program, which contained Sandea. Several Loyant treatments performed statistically similar to the grower standard herbicide program and better than the Prowl (“control”) treatment (Table 1). Loyant alone performed statistically worse than the grower standard program in this trial. While Loyant is registered for yellow nutsedge in other states, lack of moisture can impact efficacy. The delay in establishing the permanent flood may have affected its efficacy in this trial. At 64 DAT, we observed that Echinochloa grasses had grown in the Prowl treatment, but they were controlled with the other treatments. The observations agree with the 2019 and 2020 trial results, where Loyant and Loyant tank mixes showed good efficacy on Echinochloa spp.
Table 1. Percent weed control, as plot area, was estimated on 7-day intervals from 14 days after treatment (DAT) to 35 DAT. An untreated area of the field had approximately 1-4 sedges per square foot.
We also had a non-replicated demonstration site (on a different farm) where we evaluated post-flood applications of Loyant alone and in tank mixes. Treatments were applied in late-June, when grasses were heading, with the purpose of evaluating efficacy on grasses that had escaped the pre-flood grower standard program. No crop injury was observed with any treatments. Weed control was compared to a non-treated area outside of the demonstration area. All treatments had efficacy on grasses, but the Loyant/Clincher treatment appeared to work best under these circumstances.
Conclusions:
The purpose of the trial was to learn the crop tolerance and weed control efficacy of Loyant (florpyrauxifen-benzyl) in drill-seeded rice, with the specific objective in 2021 to evaluate efficacy on yellow nutsedge. The best treatment for yellow nutsedge control in this trial was the grower standard program. Loyant, alone, was not efficacious on yellow nutsedge, but performed well in tank mixes with other products. Three years of results trialing Loyant in the Delta drill-seeded system indicate that it could be used in herbicide programs, providing a different chemistry for herbicide resistance management.
The aforementioned information on products and practices is for educational purposes only and does not constitute an endorsement or recommendation by the University of California.
- Author: Michelle Leinfelder-Miles
- Author: Mick Canevari
Common purslane is a summer, annual weed that thrives under warm, moist soil conditions. It has succulent stems and leaves, grows prostrate, and is a prolific seeder. Under the right conditions, fleshy stems that break away can re-root and increase infestation. Common purslane is edible and does not present any toxicity problems for livestock. There are cultural, biological, and chemical approaches to controlling common purslane. In agricultural systems, cultivation will help manage this weed when the plants are in the seedling stage, and both pre-emergence and post-emergence herbicides are effective. More information on the biology and management of common purslane is available from UC IPM.
The moisture content of common purslane stems and leaves presents a problem when it is raked into alfalfa hay and baled. With moisture in the stems, the stems are still respiring. The process of respiration produces heat. If the heat cannot dissipate, there is the potential for the hay to catch fire. Dan Putnam, UC Alfalfa and Forage Specialist, describes this in a blog post. He explains how it is critical to monitor the hay curing process and stem moisture, and he provides some guidelines for bale moisture content. This situation with common purslane is a variation on the same theme. Moisture within the bales from the purslane presents the potential for trapped heat, so it is important to control this weed, monitor bale moisture, and stack bales so that heat can dissipate.
Glyphosate tolerance, or Roundup Ready technology, is available in alfalfa. Weed control in Roundup Ready alfalfa has been reported by UC Cooperative Extension weed scientists. In stand establishment studies, Roundup controlled common purslane in the seedling stage, but efficacy was reduced on mature plants. Additionally, there is the potential for this broad-spectrum herbicide to have reduced efficacy when used repeatedly. Under conditions of repeated use, a shift in weed species populations may occur to favor weeds like common purslane.
So now, let's go back to the present situation and this PCA's consideration to control common purslane with Shark. Shark is a PPO inhibitor, also classified as a contact herbicide. These herbicides will burn leaves and stems and are most effective on broadleaf weeds. Shark was approved for use in California alfalfa in 2014 and can be used in the winter when the alfalfa is dormant or in-season between cuttings. It can also be tank-mixed with other products, like glyphosate. (Note: always consult the label before making applications.) Another herbicide of the same chemistry class, Sharpen (saflufenacil), was approved in 2016 but only for winter-dormant alfalfa. Growers should be aware, however, that contact herbicides will burn alfalfa, and the best weed control will occur on smaller weeds and with thorough coverage of the herbicide. Alfalfa regrowth could potentially be reduced in the next cutting by the equivalent of 1-2 weeks of growth, but the crop should resume regular growth, and yield should recover. See this presentation for information on weed control in established alfalfa fields.