Foliar-applied Herbicides Research Articles

Sublethal dosing exposure risk of kochia (Bassia scoparia (L.) A.J. Scott) to carfentrazone-ethyl

Kochia is a troublesome, multiple herbicide-resistant tumbleweed which infests Prairie field crops. Kochia has developed resistance to systemic, foliar-applied herbicides from groups 2, 4, and 9, leaving only contact herbicides for post-emergence control. Group 14 chemistry is an important mode of action for resistance management. Weed staging considerations are important as recurrent sub-lethal herbicide exposure can increase risk of nontarget site resistance evolution. The study objective was to evaluate loss-of-control and estimate sublethal dosing exposure risk (SLDER) with a contact-type herbicide (carfentrazone-ethyl) based on initial kochia height, leaf number, and branch number. The SLDER from a single application to a single plant was conceptualized to increase due to escaping plant “volume” or immediate flowering. Kochia was only consistently controlled (100% injury) when dosed at ≤5 cm in height. The estimated maximum size for treated kochia was 21 cm in height, 18 branches plant−1, and the maximum accumulated biomass was between 2.6 and 5.1 g plant−1 for models developed using the initial plant height, branch number, or leaf number as predictors. These estimates represent the largest plant escapes, which would be associated with 100% risk through vegetative considerations into SLDER. Kochia plant size for a 5% risk scenario using the SLDER model was 4 cm in height, 0 branches plant−1, and 11 leaves plant−1 when carfentrazone-ethyl was applied at the labeled dosing. Caution is advised when spraying kochia above 5 cm as incorrect staging may lead to sublethal exposure, escape, reproduction, and escalated risk of nontarget site resistance evolution.

Comparative metabolomics and transcriptomics provide new insights into florpyrauxifen-benzyl resistance in Echinochloa glabrescens.

Echinochloa glabrescens Munro ex Hook. f. is a weed of the genus Echinocloa (Echinocloa spp.) that occurs frequently in paddy fields, causing serious harm to rice production. Florpyrauxifen-benzyl (FPB) is a foliar-applied herbicide used to control Echinocloa spp. in paddy fields. However, in recent years, with the widespread use of FPB in rice production, FPB-resistant barnyard grasses have been reported. Here, we identified an FPB-resistant E. glabrescens population with a resistance index (RI) of 10.65 and conducted a comparative analysis using untargeted metabolomics and transcriptomics to investigate the differences between an FPB-resistant E. glabrescens population and a susceptible E. glabrescens population after treatment with the recommended field dose of FPB. Our results showed that the FPB-resistant E. glabrescens had 115 differentially accumulated metabolites (DAMs; 65 up-regulated and 50 down-regulated) and 6397 differentially expressed genes (DEGs; 65 up-regulated and 50 down-regulated) compared to the susceptible E. glabrescens. The analysis of DAMs and DEGs revealed that DAMs were significantly enriched in Glutathione metabolism, Arginine and proline metabolism, and Zeatin biosynthesis pathways, while DEGs were mainly enriched in carbon fixation in photosynthetic organisms, photosynthesis, cyanoamino acid metabolism and glutathione metabolism, etc. The glutathione metabolism pathway was found to be significantly enriched for both DEGs and DAMs. Within this pathway, the metabolites (spermine) and genes (GSTU8, GSTU18, GSTF1) may play a pivotal role in the resistance mechanism of FPB-resistant E. glabrescens. Furthermore, we demonstrated the presence of GST-mediated metabolic resistance in an FPB-resistant E. glabrescens population by using NBD-Cl. Overall, our study provides new insights into the underlying mechanisms of E. glabrescens resistance to FPB through a comparative analysis of untargeted metabolomics and transcriptomics. Additionally, we identified the GST-mediated metabolic resistance in an FPB-resistant E. glabrescens population, and screened for three candidate genes (GSTU8, GSTU18, GSTF1), which has significant implications for improving the weed management efficacy of FPB in rice production and guiding judicious herbicide usage.

Echinochloa spp response to preemergence and postemergence herbicides in California rice (Oryza sativa L.)

Historically, herbicides were used for Echinochloa spp control in California rice production which led to the selection of herbicide-resistant biotypes. Field surveys were conducted across the seven major rice-growing counties in 2020 and Echinochloa spp samples including barnyardgrass (Echinochloa crus-galli (L.) P.Beauv.), junglerice (Echinochloa colona (L.) Link), late watergrass (Echinochloa oryzicola (Vasinger) Vasinger) and coast cockspur (Echinochloa walteri (Pursh) Heller) were collected. Greenhouse experiments were carried out to determine their suspected resistance to common preemergence and postemergence rice herbicides used in California in Fall and Winter of 2021. A total of 62 and 63 samples were characterized for suspected resistance to four preemergence granular and three postemergence foliar-applied herbicides, respectively. When granular herbicides were evaluated, samples suspected of resistance in Winter were a subset of samples that were suspected of resistance in Fall. Results indicate >90% of Echinochloa spp samples were resistant to thiobencarb, benzobicyclon + halosulfuron and penoxsulam when combined across species and counties. Cross-resistance between benzobicyclon + halosulfuron and penoxsulam was observed in >90% of the samples when combined across species and counties. Suspected clomazone resistance was observed in <75% of the samples when combined across species and counties. Suspected resistance to cyhalofop and propanil was observed in <50% of the samples when averaged across both runs. Multiple-resistance to foliar herbicides ranged from 48-60% of the samples across species and experimental runs. These results indicate the necessity for rotating herbicides during alternate cropping seasons and emphasizing integrating non-chemical strategies for Echinochloa spp control in California rice production.

Herbicides for monochoria (Monochoria vaginalis) control in transplanted rice

AbstractIn Iran, monochoria is a noxious weed in fields of transplanted rice. Two field experiments were conducted to assess the efficacy of soil-applied and foliar-applied herbicides to control monochoria in transplanted rice. Prepackaged herbicides (triafamone plus ethoxysulfuron applied at 40 g ai ha−1, pyrazosulfuron-ethyl plus pretilachlor applied at 382.5 g ai ha−1, and pendimethalin plus clomazone applied at 1,200 g ai ha−1) reduced monochoria biomass by 100%, 100%, and 14%, respectively; and a single application of flucetosulfuron at 30 g ai ha−1, pendimethalin at 990 g ai ha−1, thiobencarb at 2,750 g ai ha−1, and pretilachlor at 1,000 g ai ha−1 reduced monochoria biomass by 100%, 99%, 75%, and 56%, respectively, compared with a nontreated control. Tank-mixed bensulfuron-methyl at 45 g ai ha−1 applied with pretilachlor, thiobencarb, or pendimethalin provided 100% control of monochoria. Rice height, and straw and grain yield were greater after herbicide treatments than those of the nontreated and hand-weeded controls, indicating the advantages of chemical control of monochoria over manual weeding. Full-season monochoria interference reduced rice grain yield by 32%. In the second study, the herbicides triafamone plus ethoxysulfuron, flucetosulfuron, 2,4-D at 1,080 g ai ha−1, dicamba plus 2,4-D at 928 g ai ha−1, bispyribac-sodium at 31.25 g ai ha−1, bentazon plus MCPA at 1,150 g ai ha−1, pyribenzoxim at 30 g ai ha−1, and propanil at 5,400 g ai ha−1 applied to foliage at 4- to 5-leaf seedlings of monochoria provided ≥97% control and prevented 100% of its regrowth, with the exception of propanil. This study shows that monochoria control can be achieved by using a variety of residual and foliar-applied herbicides with different mechanisms of action.

American frogbit response to herbicides

Limnobium spongia (frogbit) is a free-floating aquatic plant that can produce extensive floating mats causing negative ecological, social, and economic impacts that can harm aquatic fauna (i.e., dissolved oxygen depletion) and restrict human uses of water. Literature describing effective control measures for frogbit is minimal. Efficacy of high and low doses of seven foliar-applied herbicides (2,4-D, florpyraux-ifen-benzyl, flumioxazin, glyphosate, imazamox, imazapyr, and triclopyr) were evaluated in a mesocosm setting in the summers of 2018, 2020, and 2021. Both emergent and submersed frogbit biomass were reduced at least 99% by imazamox (0.56 and 1.11 kg ai ha􀀁1) and imazapyr (0.42 and 0.84 kg ae ha􀀁1) 8 wk after treatment (WAT) compared with nontreated reference plants. Triclopyr (6.71 kg ae ha􀀁1) reduced frogbit biomass 92% and flumioxazin (0.42 kg ai ha􀀁1) reduced biomass 87 to 93% compared with reference plants. 2,4-D (2.12 and 4.24 kg ae ha􀀁1), glyphosate (2.83 and 5.67 kg ai ha􀀁1), triclopyr (3.36 kg ae ha􀀁1), florpyrauxifen-benzyl (0.02 and 0.05 kg ai ha􀀁1), and flumioxazin (0.21 kg ai ha􀀁1) did not reduce frogbit biomass 8 WAT compared with reference plants. Future research should consider the efficacy of different herbicide combinations to control frogbit, as well as the role of diluent volume per unit area, especially with imazamox and imazapyr. Field studies also will be useful in determining whether the results observed in this study will translate to management of frogbit in natural settings.

Integrated Management of Wild Oat (Avena fatua) and Feather Fingergrass (Chloris virgata) Using Simulated Grazing and Herbicides

Wild oat (Avena fatua L.) and feather fingergrass (Chloris virgata Sw.) are among the most problematic weed species in Australian winter and summer cropping systems, respectively. Pot trials were conducted in respective seasons to evaluate the integrated effect of simulated grazing and foliar-applied herbicides on the control of these weed species. Different herbicides were applied 1, 5, and 12 d after grazing on A. fatua plants and 1, 3, 7, 10, and 14 d after grazing on C. virgata. In general, the efficacy of herbicides was better on A. fatua when applied 5 or 12 d after grazing (i.e., 7–20 cm tall plants) and 7 to 14 d (i.e., 10–22 cm tall plants) after grazing on C. virgata. Clethodim 90 g a.i.·ha−1, and haloxyfop 52 and 78 g a.i.·ha−1 resulted in 100% mortality of A. fatua seedlings, irrespective of their application timings. Delayed application (5 or 12 d after grazing) of clethodim 60 g a.i.·ha−1 and pinoxaden 20 and 30 g a.i.·ha−1 resulted in 100% mortality of A. fatua. Glyphosate at the field rate (370 g a.e. ha−1) was the least effective herbicide to control A. fatua plants after grazing. Glufosinate application after grazing resulted in the greatest mortality (69 to 81%) of C. virgata. Depending on application timing, only glufosinate was able to provide complete control of C. virgata seed production. Butroxydim, clethodim, and haloxyfop were found to be promising herbicides to manage C. virgata after grazing but their applications had to be delayed by 7 to 14 d after grazing. This study identified several successful herbicide treatments that could be applied after grazing or mowing for integrated control of A. fatua and C. virgata. However, to achieve complete control of C. virgata, the application of these herbicides needs to be followed by other tools, including additional herbicide applications.

Efficacy of herbicides, herbicide combinations and herbicide tank mixtures on lentil (Lens culinaris Medik.)

Abstract. The research was conducted during 2019 - 2021 on pellic vertisol soil type. Under investigation was lentil cultivar Ilina (Lens culinaris Medik.). A total of 23 variants were investigated: untreated control, 8 herbicides – Pendistar 40 SC (pendimethalin), Dual gold 960 EC (S-metolachlor), Lentagran VP (pyridate), Challenge 600 SC (aclonifen), Zencor 600 SC (metribuzin), Wish top (quizalofop-P-ethyl), Zetrola (propaquizafop) and Passat 40 (imazamox), as well as combinations and tank mixtures between them. Soil-applied herbicides were used during the period after sowing before emergence. Foliar-applied herbicides were used during 2-3, 4-5 or 6-7 real leaf stage of the lentil. All of the herbicides, herbicide combinations and herbicide tank-mixtures were applied in a working solution of 300 l/ha. Mixing of foliar-applied herbicides was done in the tank on the sprayer. The combinations of herbicide Lentagran with soil-applied herbicides Pendistar and Dual gold, as well as herbicides Challenge with foliar-applied herbicides Wish top and Zetrola had an additive effect on herbicide efficacy. The herbicides Lentagran and Zencor, as well as their combinations, successfully controlled Clearfield and ExpressSun sunflower self-sown plants in lentil crops. The foliar-applied herbicide Passat controlled all annual and perennial broadleaved and graminaceous weeds and self-sown plants. The use of foliar-applied herbicide Passat and soil-applied herbicide Zencor at a dose of 900 g/ha led to high phytotoxicity in lentil plants – rate 3 according to the scale of EWRS. Double use of Zencor at doses of 600 + 300 g/ha and the combined use of the herbicides Challenge and Zetrola led to low phytotoxicity in lentil – rate 2 according to the scale of EWRS. The highest yields of lentil seeds were obtained by use of herbicide combinations Pendistar 5 l/ha + Lentagran 500 + 500 ml/ha and Pendistar 5 l/ha + Lentagran 1 l/ha. High yields were also obtained when combining Challenge 3 + 1 l/ha with Wish top 1.25 l/ha, as well as by the herbicide combination Challenge 4 l/ha + Wish top 1.25 l/ha.

Major weeds of Ecuador IV. Coffee plantations in Jipijapa

Coffee is a crop of economic importance in Ecuador, grown in area of 199 215 ha, 38,6% of it in Canton of Jipijapa, located in the south of the province of Manabí. Coffee here is grown by small farmers, who spend who spend little annually for the maintenance of plantations. One of the main constraints for getting optimal crop yields is the presence of weeds, which affect water stress during dry spells, and bring about deficient plant uptake of essential nutrients. Weeds are not usually properly controlled in all areas of this crop. Some farmers eliminate weeds twice or three times a year, others do that only once. The most common control method is hand hoeing, but some growers use foliar-applied herbicides, any of these practices are commonly carried out without knowledge of prevailing weed species. Suitable weed management strategy should include data about main weeds and their biology during dry and rainy seasons in Jipijapa. To this end, in 15 ha of coffee plantations during 2014 dry period and in another 15 ha during 2015 rainy one, weed cover and species present were visually evaluated using a scale 0-5, where 1- up to 5% weed cover and 4-more than 50%. These values were processed to determine Absolute and Relative Frequencies, average weed cover and finally Severity Infestation (SI). A total 39 weed species belonging to 19 families were found in both seasons, mostly broadleaves plants, while grasses were found in less shady spots of the plantations. The prevailing weed during rainy period appears to be Senna occidentalis followed by Commelina erecta, Laportea aestuans, Alternathera flavescens and Xanthosoma spp., while during dry season, the fern Pteridium aquilinum was the leading species followed by perennials Alternathera flavescens and the C4 grass Megathyrsus maximus. The species found only responded to the humidity conditions in each season and not to the effect of a certain control measure. Most of the evaluated plantations show poor crop management, scarce crop plant density, and even coffee planted in favor of the slope. Improved plantation management is the key measure to reduce the weed presence of weeds. In the rainy season, with more weed abundance, two early weeding operations, with an additional one later are advisable, while in the dry season, in the case of plantations with adequate shade, one weeding may satisfactorily reduce the weed presence. Perennial Geophila macropoda, found during rainy season, is a potential living cover in coffee plantations since it may help to reduce soil erosion and smothers weeds.

Performance of different herbicides on pondweed (Potamogeton nodosus) in rice

AbstractPondweed is a rhizomatous perennial weed of aquatic habitats that recently adapted to rice ecosystems in northern Iran. Two field experiments were conducted at the Rice Research Institute of Iran to determine the impact of pondweed on rice yield and identify effective herbicides for pondweed control. The focus of the first study was to evaluate the herbicides commonly used in Iranian rice, including butachlor, pretilachlor, oxadiargyl, pendimethalin, thiobencarb, and bensulfuron-methyl. None of these herbicides effectively controlled pondweed, except bensulfuron, which reduced pondweed biomass by ≥95% and produced 26% higher rough rice grain yield than the nontreated plots. The second experiment evaluated the performance of acetolactate synthase–inhibiting herbicides on pondweed control, rough rice yield, and pondweed regrowth. Herbicide efficacy on pondweed varied from 36% to 100%. Five preemergence herbicides, bensulfuron at 45 g ai ha−1, flucetosulfuron at 30 g ai ha−1, triafamone plus ethoxysulfuron at 40 g ai ha−1, and metsulfuron-methyl at 15 g ai ha−1, provided ≥98% control of pondweed. Use of postemergence herbicides penoxsulam at 35 g ai ha−1, bispyribac-sodium at 30 g ai ha−1, and pyribenzoxim at 35 g ai ha−1provided 36%, 89%, and 93% pondweed control, respectively. Rough rice yields ranged from 107% to 124% in herbicide-treated plots compared with the nontreated plots. Soil-applied herbicide treatments produced higher (≥119%) yield than the hand-weeded control or foliar-applied herbicides. Pondweed regrowth was affected by herbicides and was variable. Soil-applied residual herbicides metazosulfuron, flucetosulfuron, and metsulfuron provided complete control of pondweed and prevented regrowth. In contrast, pondweed regrowth in other soil- and foliar-applied herbicide treatments occurred, indicating their lesser translocation to underground vegetative rhizomes. This study shows that although most sulfonylurea herbicides can control pondweed effectively to achieve high rough rice yield, only a few soil-applied herbicides were able to prevent pondweed regrowth.

Efficacy of Herbicides, Herbicide Tank Mixtures and Herbicide Combinations on Express Sun Oil-Bearing Sunflower (Helianthus Annuus L.)

During the period 2018-2020 a field experiment has been carried out with the oil-bearing sunflower hybrid P64LЕ121 (Helianthus annuus L.). It is a sulfo tolerant hybrid by ExpressSun technology. A total of 25 variants were investigated. They included untreated control, 2 herbicides applied alone in addition with adjuvant Trend 90, 10 herbicide tank mixtures and 10 herbicide combinations. Soil-applied combined herbicides were performed during after sowing before emergence period of the sunflower. Foliar-applied herbicides were performed during 3-4 leaf sunflower stage. Full control of annual broadleaved weeds in ExpressSun oil-bearing is provided by a single treatment with herbicide Fluence at a dose of 40 g/ha or with herbicide Evorelle express at a dose of 60 g/ha applied during 3-4 leaf sunflower stage. Full controls of perennial broadleaved weeds is provided by two treatments with herbicide Fluence in doses of 20+20 g/ha or with herbicide Evorelle express in doses of 30+30 g/ha, applied during 3-4 leaf and 7-8 leaf sunflower stages. In the presence of annual and perennial broadleaved and graminaceous weeds, it is necessary to apply Fluence and Evorelle express as herbicide tank mixtures together with foliar-applied antigraminaceous herbicides Fusilade forte, Stratos ultra or Targa max. In the absence of perennial graminaceous weeds, it is necessary to apply herbicides Fluence and Evorelle express as herbicide combinations with soil-applied antigraminaceous herbicides Dual gold or Indipen. The highest seed yield is obtained by herbicide tank mixture Fluence + Fusilade forte, followed by herbicide tank mixture Evorelle express + Stratos ultra. High seed yields are also obtained by use of herbicide combinations Indipen + Evorelle express and Dual gold + Fluence.

Selectivity and stability of herbicides, herbicide tank mixtures and herbicide combinations on seed yield of Clearfield oilseed canola (Brassica napus L.)

Abstract. During the period 2018-2020 a field experiment was carried out with the winter Clearfield oilseed canola hybrid Phoenix CL (Brassica napus L). Factor A included the years of investigation. Factor B included untreated control, 2 combined herbicides: Cleranda SC and Cleravo SC; 6 herbicide tank mixtures: Electron 500 SC + Maza 4 SL, Springbok + Maza 4 SL, Tanaris + Maza 4 SL, Butisan max + Maza 4 SL, Cliofar 600 SL + Maza 4 SL and Galera super + Maza 4 SL; 6 herbicide combinations: Caliph 480 ЕC + Maza 4 SL, Caliph mega + Maza 4 SL, Bismark CS + Maza 4 SL, Nero ЕC + Maza 4 SL, Brasan 540 EC + Maza 4 SL and Colsor trio ЕC + Maza 4 SL. Herbicides Cleranda, Cleravo and Maza were used in addition with adjuvant Dash HC. Foliar-applied herbicides were treated during 2-4 leaf canola stage. Soil-applied combined herbicides were treated during after sowing before emergence period of the canola. It was found that: (i) the highest seed yields are obtained by use of combined herbicide Cleranda, followed by herbicide tank mixture Electron + Maza and combined herbicide Cleravo; (ii) the high canola yields are also obtained by herbicide tank mixtures Butizan max + Maza, Springbok + Maza, Tanaris + Maza, as well as by herbicide combinations Caliph mega + Maza, Brasan + Maza, Bismarck + Maza; (iii) technologically the most valuable are combined herbicide Cleranda, followed by herbicide tank mixture Electron + Maza and combined herbicide Cleravo; (iv) in terms of technology for growing winter Clearfield oilseed canola, herbicide tank mixtures Springbok + Maza, Butisan max + Maza and Tanaris + Maza, as well as herbicide combinations Caliph mega + Maza, Bismar + Maza and, Nero + Maza get high rating; herbicide tank mixtures Cliofar + Maza and Galera super + Maza and herbicide combinations Caliph + Maza and Colsor trio + Maza get low rating.

Продуктивность сорго зернового в зависимости от применения гербицидов

Abstract. The purpose of the work is to establish the effectiveness of weed in control in crops of grain sorghum with herbicides of soil and leaf action. Scientific novelty. For the first time in sorghum crops for weed control, effective combinations of soil and leaf herbicides have been identified. Methods. Experiments were carried out on the black soils of steppe zone Ukraine. Research methods are generally accepted. The control options were herbicide-free and weed-free. Results. At tillering stage the number of weeds in sorghum crops reached 141 pieces/m2 and their air-dry weight was 218 g/m2. Green amaranth (Amaranthus retroflexus), fat hen (Chenopodium album), field mustard (Sinapis arvensis), ragweed ragweed (Ambrosia artemisiifolia), barnyard grass (Echinochloa crus-galli), bristlegrass (Setaria viridis) were dominant in the crops. The use of foliar-applied herbicides such as Agritox (1 l/ha), Ballerina (0.4 l/ha), Dialen Super (0.7 l/ha) in the stage of three-five leaves and a pre sowing soil-applied herbicide Primextra Gold (3 l/ha) ensured the maximum reduction of weed infestation of grain sorghum crops. The number of weeds with the use of these herbicides decreased by 10.4–19.7 times, and their weight decreased by 4.1–4.8 times in comparison with the options without the use of weed control measures. The conditions for plant growth and development were improved due to the reduction of weed infestation of grain sorghum crops. The growing period of the crop reduced from 125 to 114 days, the height of plants increased by 19–21 cm and their weight increased by 2.7–2.8 times. The sorghum grain yield reached 6.32–6.34 t/ha, which was higher than with the options without the use of weed control measures by 4.01–4.30 t/ha or 3.0–3.1 times. The same results were obtained in production conditions.

Chemical control of suckers in hazelnut orchards of western Oregon

AbstractHazelnut naturally grows as a multi-stemmed tree. The basal sprouts, known as suckers, grow throughout the season. Suckers are removed to promote a single trunk that facilitates production mechanization and increased yield. In western Oregon, herbicides are the most common method of sucker control, and at least four applications per season are performed in the spring and summer seasons. This study evaluated the efficacy of foliar-applied herbicides currently registered for sucker control in hazelnuts. Season-long and short-term field studies were conducted to assess the efficacy of herbicides to control hazelnut suckers. In the season-long studies, four consecutive applications of treatments that contained 2,4-D, glufosinate, or paraquat provided 50% to 80% control, maintained sucker height at 50 cm or less as compared to 155 cm for the nontreated control, and reduced sucker biomass by 87% as compared to the nontreated control. The short-term study results confirmed the efficacy of 2,4-D, glufosinate, and paraquat for sucker control, and in this study, carfentrazone and saflufenacil reduced sucker biomass to a level comparable to 2,4-D or glufosinate treatment. These results confirm that 2,4-D, glufosinate, paraquat, carfentrazone, and saflufenacil can be used for sucker control in hazelnut and emphasize the necessity of multiple applications during the growing season to control suckers in hazelnut. Proper herbicide selection is important to control suckers with success.

Season-long weed control with sequential herbicide programs in California tree nut crops

AbstractWeed control in tree nut orchards is a year-round challenge for growers that is particularly intense during winter through summer as a result of competition and interference with management and harvest operations. A common weed control program consists of an application of a winter PRE and POST herbicide mixture, followed by a desiccation treatment in early spring and before harvest. Because most spring and summer treatments depend on a limited number of foliar-applied herbicides, summer-germinating species and/or herbicide-resistant biotypes become troublesome. Previous research has established effective PRE herbicide programs targeting winter glyphosate-resistant weeds. However, more recently, growers have reported difficulties in controlling several summer-germinating grass weeds with documented or suspected resistance to the spring and summer POST herbicide programs. In this context, research was conducted to evaluate a sequential PRE approach to control winter- and summer-germinating orchard weeds. Eight field experiments were conducted in tree nut orchards to evaluate the efficacy of common winter herbicide programs and a sequential herbicide program for control of a key summer grass weed species. In the sequential-application strategy, three foundational herbicide programs applied in the winter were either mixed with pendimethalin, followed with pendimethalin in March, or applied as a split application of pendimethalin in both winter and spring. Results indicate that the addition of pendimethalin enhanced summer grass weed control throughout the crop growing season by up to 31%. Applying all or part of the pendimethalin in the spring improved control of the summer grass weed junglerice by up to 49%. The lower rate of pendimethalin applied in the spring performed as well as the high rate in the winter, suggesting opportunities for reducing herbicide inputs. Tailoring sequential herbicide programs to address specific weed challenges can be a viable strategy for improving orchard weed control without increasing herbicide use in some situations.

Emergence of Glyphosate- and Glufosinate-resistant Italian Ryegrass (<i>Lolium multiflorum</i>) Populations in Japanese Pear Orchards in Japan and their Responses to Several Foliar-applied Herbicides

Emergence of Glyphosate- and Glufosinate-resistant Italian Ryegrass (<i>Lolium multiflorum</i>) Populations in Japanese Pear Orchards in Japan and their Responses to Several Foliar-applied Herbicides

After-effect of Foliar-Applied Herbicides for Broad-leaved Weeds on the Primary Germ Length of Cotton Seeds (Gossypium Hirsutum L.)

The trial was carried out during 2013-2015, with twelve cotton cultivars (Gossypium hirsutum L.). Influence of herbicides Bazagran 480 SL (bentazone), Pulsar 40 (imazamox) and Express 50 VG (tribenuron-methyl) was studied. These herbicides were used during the budding stage of cotton. The herbicide Bazagran 480 SL has the highest phytotoxicity on the primary germ length of seeds of cotton cultivars Chirpan-539 and Trakia and the lowest on cultivar Natalia. The herbicide Pulsar 40 has the highest phytotoxicity on the primary germ length of seeds of cotton cultivar Dorina and the lowest on the cultivars IPK-Veno and Viki. The herbicide Express 50 VG has the highest phytotoxicity on the primary germ length of seeds of the cotton cultivar Chirpan-539 and the lowest on the cultivars Helius and Trakia. From the viewpoint of cotton growing technology, technologically the most valuable are all cultivars, by foliar treatment with herbicide Bazagran 480 SL. Technologically the most valuable are cultivars Viki, IPK-Veno, Boyana and Natalia by foliar treatment with herbicide Pulsar 40. Technologically the most valuable are cultivars Helius, Trakia, Viki, Avangard and Nelina by foliar treatment with herbicide Express 50 VG. These variants combine high primary germ lengths and high stability of this index during the different years.

After-effect of foliar-applied herbicides for broad-leaved weeds on the primary germ weight of cotton seeds (Gossypium hirsutum L.)

Abstract. The trial was carried out during 2013-2015, with twelve cotton cultivars (Gossypium hirsutum L.). Influence of herbicides Bazagran 480 SL (bentazone)- 1.5 L/ha, Pulsar 40 (imazamox) – 1.2 L/ha and Express 50 VG (tribenuron-methyl) – 50 g/ha was studied. These herbicides were used during the budding stage of cotton. From the viewpoint of cotton growing technology, technologically the most valuable are cultivars Helius, Trakia, Viki, Filipopolis, Boyana, Avangard, Natalia, Darmi, Dorina and Nelina, in foliar treatment with herbicide Bazagran 480 SL. Technologically the most valuable are cultivars Chirpan-539, Helius, Viki, Boyana and Natalia in foliar treatment with herbicide Pulsar 40. Technologically the most valuable are cultivars Helius, Trakia, Viki and Nelina in foliar treatment with herbicide Express 50 VG. These variants combine high primary germ weight and high stability of this index during the different years.

A comparison of three foliar-applied herbicides for controlling mountain laurel thickets in the mixed-oak forests of the central Appalachian Mountains, USA

In the Appalachian Mountains of eastern North America, mountain laurel (Kalmia latifolia) thickets in mixed-oak (Quercus spp.) stands can lead to hazardous fuel conditions, forest regeneration problems, and possible forest health concerns. Generally, land managers use mechanical means or prescribed fire to control mountain laurel thickets, but these treatments are expensive, dangerous to implement, or have short-term effectiveness. From 2012 to 2016, we compared the effectiveness of three herbicides applied as broadcast foliar treatments at varying rates and in different months for reducing mountain laurel thickets. Triclopyr (ester formulation) top-killed mountain laurel within a few weeks at most month/rate combinations, but subsequent sprouting reduced overall effectiveness by year 3. Conversely, imazapyr provided little initial control of mountain laurel, but by year 3, the herbicide had killed nearly all the treated shrubs with no subsequent sprouting regardless of the month of application or rate. Glyphosate had limited effectiveness; spraying in August at 8 and 12 L/ha killed the mountain laurel over 3 years with little sprouting while all others treatments had little or no impact. From these results, it appears that several month/rate combinations of all three herbicides have potential for controlling mountain laurel thickets and merit further testing to refine application procedures.

Effects of application date and rate of foliar-applied glyphosate on pine seedlings in Turkey

Glyphosate is the herbicide most extensively used for site preparation and conifer release. It is a broad-spectrum herbicide and therefore crop safety is a critical issue. This study assessed the early effects of 14 different treatments, including no weed control, manual weed control, and 12 foliar-applied herbicide treatments at low, intermediate, high, and highest application rates and application timing on glyphosate phytotoxicity of containerized seedlings of Austrian pine (Pinus nigra J.F. Arnold.), Scots pine (P. sylvestris L.) and maritime pine (P. pinaster Aiton), conifer species widely used for afforestation and supplementary plantings in Turkish forestry. In general, Scots pine seedlings were tolerant to glyphosate compared to the other species. Glyphosate phytotoxicity varied significantly according to the time and rate of application. Seedlings were relatively tolerant to glyphosate in April whereas they were intolerant in May. The highest herbicide rate (1.2% v:v) was consistently phytotoxic to all species. Moreover, the effect of herbicide rate on seedling survival and growth varied significantly according to application date (i.e., application rate × date interaction). Seedlings appeared tolerant to glyphosate at low and intermediate rates (0.2, 0.4% v:v) between mid-spring and mid-summer, whereas they demonstrated significant sensitivity to the highest rate across all time periods. Glyphosate at the high rate (0.8% v:v) was particularly more phytotoxic when applied in May. Application of glyphosate at rates up to 0.8% could be recommended for weed control without significant pine damage in mid-spring when the needles presumably have a dense leaf epicuticular wax layer limiting herbicide penetration. Applications of 0.8 and 1.2% v:v are not recommended during May–June.

Mixture B New Formulation adjuvant increases the rainfastness and hence effectiveness of glyphosate for rhododendron control

Rhododendronponticum(L.)isahighlyinvasiveandcompetitiveweedonmanyforestsitesinBritainandcanactas a host for the pathogens Phytophthora ramorum(Werres) and P. kernoviae(Brasier). Control of rhododendron can be difficult due in part to itsthick waxy leafsurfaces, which discourage the absorption of foliar-applied herbicides. The adjuvant Mixture B has been used for many years to improve efficacy, absorption and rainfastness of glyphosateusedforrhododendroncontrol,buttheformulationhaschanged,andthenewproduct,‘MixtureBNF’,hasnot beenindependentlytested.Anexperimentwasthereforesetuptotesttheeffectofaddingoneofthreeadjuvants (MixtureB,MixtureBNForBreak-ThruS240),totwoexampleglyphosateproducts(RoundupProBiactiveandClinic Ace) and one triclopyr product (Timbrel) on the control of rhododendron plants. Treatments were applied as foliar spraysandthensubjectedtofourdifferentartificialrainfallregimestoexaminerainfastness.Rainfallhadnoeffect on the efficacyof Timbrel, which performed well with or without adjuvants. Rainfall afterapplication reduced the efficacyofbothRoundupProBiactiveandClinicAce,butitmadenodifferenceiftherainfalloccurred1,3or6 hafter application. There were no differences between the effectiveness of the different glyphosate formulations, but the rainfastness of both products were substantially increased by both Mixture B and Mixture B NF. The adjuvant Break-ThruS240gavelittlebenefit.Itisrecommendedthatwhenfoliarspraysofrhododendronbushesarerequired, iftriclopyrisnotavailable,anequivalentof2.88 kg a.i. ha 21 glyphosateshouldbeused(e.g.as8 l ha 21 RoundupPro Biactive or Clinic Ace) and Mixture B NFadjuvant added at a rate of 2 per cent of final spray volume.