diseases (Rogers et al., 2006). Weeds Tank Mix of Saflufenacil with Glyphosate and around tree trunks may create a favor- Pendimethalin for Broad-spectrum Weed able environment for pathogens that infect the trunk and roots (Futch and Control in Florida Citrus Singh, 2010). Direct reduction in tree growth and yield may occur when weed infestation is very dense; however, not Megh Singh, Mayank Malik, Analiza H.M. Ramirez, all the weeds compete with citrus trees and Amit J. Jhala1 in the same level of competition. Weed management in citrus groves greatly varies depending on the type ADDITIONAL INDEX WORDS. broadleaf weeds, grass weeds, herbicides, percent of crop, producer, location, and avail- control, postemergence ability of resources. Citrus growers use SUMMARY. Citrus (Citrus spp.) is one of the most important crops in Florida a combination of mechanical, chemical, agriculture. Weed control is a major component in citrus production practices. If and cultural methods to control weeds. not controlled, weeds may compete with citrus trees for nutrients, water, and light Among various methods of weed con- and may also increase pest problems. Herbicides are an important component of trol, herbicides are an important choice integrated weed management program in citrus. Saflufenacil, a new herbicide commonly used by citrus growers ei- registered for broadleaf weed control in citrus, can be applied alone or in a tank ther as strip applications within the crop mix with other herbicides to improve weed control efficacy. A total of six field row or as broadcast applications to the experiments were conducted in 2008 and 2009 to evaluate the efficacy of grove floor (Sharma et al., 2008). Non- saflufenacil applied alone or in a tank mix with glyphosate and pendimethalin for bearing young citrus trees (<4 years weed control. In addition, experiments were also conducted to evaluate phytotox- icity of saflufenacil applied at different rates and time intervals in citrus. The results old) require greater attention to her- suggested that saflufenacil applied alone was usually effective for early season bicide selection and application rates broadleaf weed control; however, weed control efficacy reduced beyond 30 days because the area around the tree is after treatment (DAT) compared with a tank mix of saflufenacil, glyphosate, and more exposed to sunlight and have pendimethalin. For example, control of weeds was £70% when saflufenacil or greater weed pressure compared with glyphosate applied alone compared with tank mix treatments at 60 and 90 DAT. older trees (Futch and Singh, 2000). Addition of pendimethalin as a tank mix partner usually resulted in better residual Because of its broad weed spectrum, weed control compared with a tank mix of saflufenacil and glyphosate, and this relatively low cost, and favorable envi- herbicide mixture was comparable with grower’s adopted standard treatment of ronmental profile, glyphosate is used ex- a tank mix of glyphosate, norflurazon, and diuron and several other tank mix tensively in Florida citrus crops (Sharma treatments. Saflufenacil applied once in a season at different rates or even in sequential applications did not injure citrus trees when applied according to label and Singh, 2007). Although glypho- directions. It is concluded that with its novel mode of action, saflufenacil tank mixed sate is a broad-spectrum herbicide, not with glyphosate and pendimethalin would provide citrus growers with another all weeds are equally susceptible to it chemical tool to control broadleaf and grass weeds. (Culpepper and York, 2000). For ex- ample, barnyardgrass (Echinochloa crus- galli) is more sensitive to glyphosate lorida is the largest producer estimated that by 2020, it will be $10.8 compared with velvetleaf (Abutilon the- of citrus including grapefruit billion (Spreen et al., 2006). ophrasti) (Taylor, 1996). F(Citrus paradisi), sweet orange Because of warm weather and fre- Overreliance on a single herbicide (Citrus sinensis), mandarin (Citrus retic- quent rainfall, weed management is could result in loss of effectiveness be- ulata), and mandarin hybrid cultivars in an annual challenge for citrus growers cause of selection pressure, which re- the United States and the second largest in Florida to reduce weed competi- sults in evolution of herbicide-resistant in the world (following Brazil) [U.S. tion as well as minimize weed inter- weeds (Powles, 2008). Glyphosate is Department of Agriculture (USDA), ference with horticultural operations the dominant herbicide used extensively 2006]. In 2010, citrus was grown on (Futch and Singh, 2007). Weed com- in many countries for many years (Duke more than 550,000 acres in Florida petition is damaging to citrus trees, and Powles, 2008). The occurrence of (USDA, 2010a) with the production especially when they are young, be- weed shifts and selection of glyphosate- of over 159 million boxes, which ac- cause it slows the tree growth and in- resistant biotypes in the United States counted for about 65% of the total creases susceptibility to insects and and many other countries led to an U.S. production (USDA, 2010b). Florida citrus industry is the main eco- nomic force in the state. Total esti- Units mated economic impact of the citrus To convert U.S. to SI, To convert SI to U.S., industry in the 2003–04 was $9.3 bil- multiply by U.S. unit SI unit multiply by lion in Florida’s economy, and it is 0.4047 acre(s) ha 2.4711 0.3048 ft m 3.2808 9.3540 gal/acre LÁha–1 0.1069 Citrus Research and Education Center Institute of 2.54 inch(es) cm 0.3937 Food and Agricultural Sciences, University of Florida, 0.1198 lb/100 gal kg/100 L 8.3454 700 Experiment Station Road, Lake Alfred, FL 33850- 1.1209 lb/acre kgÁha–1 0.8922 2299 70.0532 oz/acre gÁha–1 0.0143 1Corresponding author. E-mail: amit@ufl.edu. 6.8948 psi kPa 0.1450
606 • October 2011 21(5) increased need for alternative herbi- methods to reduce herbicide rates while the phytotoxicity of saflufenacil on cide programs including tank mix of maintaining weed control at acceptable citrus trees. herbicides with different mode of ac- levels (Green, 1991) and controlling tion (Beckie, 2006). Currently, 21 weed herbicide-resistant weeds (Beckie, 2006). Materials and methods species have evolved resistance to glyph- Saflufenacil is a broadleaf herbicide; 2008. Two field experiments were osate worldwide (Heap, 2011); how- therefore, it must be tank mixed with conducted in a citrus grove at Polk City, ever, there is no confirmed report of a grass herbicide or a broad-spectrum FL, in 2008 to evaluate the efficacy of glyphosate-resistant weed in Florida herbicide such as glyphosate for better saflufenacil applied alone or in a tank citrus. Therefore, a strategy is required weed control program. Saflufenacil has mix with glyphosate and pendimetha- to avoid the glyphosate-resistant weeds been tank mixed with dimethenamid- lin for weed control. The soil of the in Florida citrus by identifying new P and registered as VerdictTM (BASF experimental site was Florida Candler herbicide chemistry with a different Corp.) for preemergence control of fine sand (hyperthermic, uncoated, mode of action. Fortunately, a few new annual grasses, broadleaf weeds, and Typic Quartzipsamment). The experi- herbicides are in the process of regis- sedges in maize, grain sorghum (Sor- ments were laid-out in a randomized tration or have recently been registered ghum bicolor), and soybean (BASF complete block design with four rep- for weed control in citrus. For exam- Corp., 2010d). Saflufenacil has also lications. The details of herbicide treat- ple, saflufenacil, commercially known been tank mixed with imazethapyr and ments applied in Expts. 1 and 2 are as TreevixTM (BASF Corp., Research registered as OptilTM (BASF Corp.) for listed in Tables 1 and 2, respectively. Triangle Park, NC) is a new postemer- use in imidazolinone-resistant maize, All herbicide treatments were applied gence, contact herbicide for broadleaf soybean, and field pea (Pisum sativum) using a tractor-mounted computer- weed control in bearing and nonbear- (BASF Corp., 2010a). ized boom sprayer fitted with 8002 TM ing citrus fruit trees (BASF Corp., Pendimethalin (Prowl H2O , Teejet nozzles (Spraying System Co., 2010c). Saflufenacil is also registered BASF Corp.) is a preemergence, re- Wheaton, IL) and an off center OC-4 as SharpenTM (BASF Corp.) for broad- sidual herbicide registered for control flat spray tip, delivering 20 gal/acre leaf weed control in chickpea (Cicer of annual grasses and some broadleaf spray volume at 30 psi. The plot size arietinum), maize (Zea mays), cot- weeds in Florida citrus (BASF Corp., was 3 · 18 m, covering five citrus trees ton (Gossypium hirsutum), soybean 2009), but it is less effective on sedges per plot. The trees were 3 years old (Glycine max), and some other crops and some hard-to-control broadleaf when herbicides were applied.The her- (BASF Corp., 2010b). weeds such as shepherd’s-purse (Cap- bicide treatments in both the experi- Saflufenacil is a uracil-based her- sella bursa-pastoris)andspreadingday- ments were applied on 25 June 2008 bicide, which is a potent inhibitor of flower (Commelina diffusa) (personal when weeds were about 10 to 15 cm protoporphyrinogen oxidase [PPO observation). Weed control spectrum tall. All herbicide treatments included (also known as protox)] (Grossman of pendimethalin can be expanded by ammonium sulfate applied at 2.03 kg/ et al., 2010). The PPO-inhibiting tank mixing with other residual her- 100 L solution and crop oil concen- herbicides competitively inhibit PPO bicides such as diuron; for controlling trate at 1% v/v. Visual percent control by occupying the binding site for existing weeds, it can be tank mixed of grass and broadleaf weeds was re- Protogen IX (Duke et al., 1991), with glyphosate or paraquat (BASF corded at 7, 15, 30, 60, and 90 DAT which results in a rapid loss of mem- Corp., 2009). It is expected that when on a scale 0% to 100%, where 0% being brane integrity and tissue necrosis and saflufenacil would be tank mixed with no control and 100% being complete death of plant. Saflufenacil is translo- a postemergence herbicide such as control of all weeds at the time of ob- cated mainly in the xylem with limited glyphosate and a residual herbicide such servation compared with untreated mobility in the phloem (Liebl et al., as pendimethalin, the combination will control. Phytotoxicity of herbicide treat- 2008). It is readily absorbed by plant provide control of existing weeds as mentsoncitrustreeswasalsoevaluated roots, shoots, and leaves. The injury well as extended residual weed con- based on a 0% to 100% scale, where 0% symptoms on susceptible broadleaf trol in Florida citrus. This tank mix- being no injury and 100% being com- species appear within a few hours, and ture could also be effective for control plete death of the citrus tree. plant die generally within 1 to 3 d un- of herbicide-resistant weeds. For ex- Two field experiments were con- der normal application and environ- ample, Owen et al. (2011) reported ducted at Haines City, FL, and Dundee, mental conditions (Liebl et al., 2008). 94% control of glyphosate-resistant FL, in 2008 to evaluate phytotoxicity Saflufenacil is applied at relatively low horseweed (Conyza canadensis) with of saflufenacil applied alone or in a rates. The label rate of saflufenacil ap- the application of saflufenacil before tank mix with glyphosate in young plied as a postemergence in citrus is 1 planting cotton. citrus trees. The treatments included oz/acre plus the recommended adju- There is no information available glyphosate (Roundup WeathermaxTM; vant in a single application with a max- on weed control with tank mixes of Monsanto, St. Louis, MO) applied alone imum cumulative annual amount of saflufenacil, glyphosate, and pendime- at 2.25 lb/acre, saflufenacil applied 3 oz/acre (BASF Corp., 2010c). It can thalin at different rate combinations alone at 2 or 4 oz/acre or in a sequential be applied as a single application or in Florida citrus. Therefore, the ob- application after 2 months, and saflu- sequentially up to three times per year. jectives of this study were 1) to eval- fenacil at 2 oz/acre tank mixed with If applied sequentially, it must be sep- uate the efficacy of saflufenacil applied glyphosate at 2 lb/acre. The experi- arated by at least 21 d (BASF Corp., alone and tank mix of saflufenacil, mental design was a randomized com- 2010c). glyphosate, and/or pendimethalin at plete block with four replications. The A tank mix of herbicides with dif- various rates for weed control in estab- herbicide treatments were manually ferent mode of action is one of the lished citrus groves and 2) to evaluate applied with a knap sack sprayer at
• October 2011 21(5) 607 RESEARCH REPORTS
Table 1. Effects of herbicide treatments on control of grass and broadleaf weeds in Expt. 1 conducted at Polk City, FL, in 2008. Grass weeds (% control)y Broadleaf weeds (% control)y Herbicide treatmentz 7 DATx 15 DAT 30 DAT 60 DAT 90 DAT 7 DAT 15 DAT 30 DAT 60 DAT 90 DAT Untreated control 0 c 0 d 0 d 0 d 0 e 0.0 c 0.0 e 0 c 0 d 0 d Glyphosate 1 lb/acre 69 b 87 b 85 abc 71 b 62 c 64 c 79 cd 84 b 71 c 52 c Saflufenacil 1 oz/acre 74 ab 80 c 79 c 60 c 54 d 70 bc 74 d 81 b 70 c 57 c Saflufenacil 1 oz/acre + 79 a 89 b 82 bc 76 b 71 b 75 ab 87 ab 91 a 77 c 70 b glyphosate 1 lb/acre Glyphosate 1 lb/acre + 77 a 100 a 87 ab 96 a 91 a 70 bc 82 bc 95 a 91 ab 90 a pendimethalin 140 oz/acre Saflufenacil 1 oz/acre + 81 a 100 a 94 a 97 a 94 a 79 ab 90 ab 96 a 96 a 91 a glyphosate 1 lb/acre + pendimethalin 160 oz/acre Saflufenacil 1 oz/acre + 79 a 99 a 91 ab 94 a 92 a 74 b 87 ab 95 a 92 ab 90 a glyphosate 1 lb/acre + pendimethalin 140 oz/acre Glyphosate 1 lb/acre + 81 a 97 a 91 ab 91 a 91 a 82 a 95 a 95 a 87 b 86 a norflurazon 2.4 lb/acre + diuron 13 lb/acre zAll herbicide treatments included ammonium sulfate at 2.03 kg/100 L (16.941 lb/100 gal) solution and crop oil concentrate at 1% v/v; 1 lb/acre = 1.1209 kgÁha–1, 1 oz/acre = 70.0532 gÁha–1. yData were arcsine transformed for homogenous variance before analysis; however, data presented here are the means of actual values for comparison. Least square means within columns with no common letters are significantly different according to Fisher’s protected least significant difference test where P < 0.05. xDays after treatment.
Table 2. Effects of herbicide treatments on control of grass and broadleaf weeds in Expt. 2 conducted at Polk City, FL, in 2008. Grass weeds (% control)y Broadleaf weeds (% control)y Herbicide treatmentz 7 DATx 15 DAT 30 DAT 60 DAT 90 DAT 7 DAT 15 DAT 30 DAT 60 DAT 90 DAT Untreated control 0 c 0 d 0 d 0 d 0 e 0 e 0 e 0 d 0 d 0 d Glyphosate 1 lb/acre 72 b 86 ab 85 b 75 b 70 c 66 d 80 bc 81 bc 70 c 65 bc Saflufenacil 1 oz/acre 70 b 79 b 75 c 65 c 59 d 70 cd 77 c 77 c 69 c 60 c Saflufenacil 1 oz/acre + 77 ab 87 ab 87 b 82 b 79 b 74 bcd 86 ab 85 b 79 b 74 b glyphosate 1 lb/acre Glyphosate 1 lb/acre + 79 ab 86 ab 91 ab 92 a 91 a 80 ab 89 ab 94 a 92 a 89 a pendimethalin 80 oz/acre Saflufenacil 2 oz/acre + 81 ab 87 ab 94 ab 81 b 76 bc 77 abc 87 ab 91 a 81 b 67 bc glyphosate 1 lb/acre Saflufenacil 1 oz/acre + 82 a 92 a 96 a 96 a 95 a 82 a 92 a 95 a 96 a 92 a glyphosate 1 lb/acre + pendimethalin 80 oz/acre zAll herbicide treatments included ammonium sulfate at 2.03 kg/100 L (16.941 lb/100 gal) solution and crop oil concentrate at 1% v/v; 1 lb/acre = 1.1209 kgÁha–1, 1 oz/acre = 70.0532 gÁha–1. yData were arcsine transformed for homogenous variance before analysis; however, data presented here are the means of actual values for comparison. Least square means within columns with no common letters are significantly different according to Fisher’s protected least significant difference test where P < 0.05. xDays after treatment.
20 gal/acre spray volume at 30 psi. The 2009. A field experiment was The applications were made using a plot size was 3 · 15 m, covering four conducted in a grapefruit grove at Frost- tractor mounted sprayer as explained trees per plot. The citrus trees were proof, FL, to evaluate efficacy of saflu- in previous experiment. Visual per- 2 years old when herbicides were fenacil applied alone or in a tank mix cent control of weed species and pot- sprayed. Treatments were applied at dif- for controlling weeds. Soil type was ential injury on citrus was evaluated ferent time intervals on 29 Apr. 2008, same as explained in 2008 study. The at 15, 30, 45, 60, and 90 DAT as per 30 June 2008, and 29 Aug. 2008. All treatment detail is presented in Tables the procedure explained in previous treatments included ammonium sul- 3 and 4. The herbicide applications experiments. fate applied at 2.03 kg/100 L solu- were made on 1 May 2009. The ad- A field experiment was conducted tion and crop oil concentrate at 1% v/ juvants methylated seed oil (1% v/v) in a citrus grove at the Citrus Research v. Citrus injury was visually estimated and ammonium sulfate (2.03 kg/100 and Education Center, University of at 7, 15, and 30 DAT using the L) was added to all herbicide treat- Florida, Lake Alfred. The citrus crop was procedure described in the previous ments. The grapefruit trees were 3 years ‘Valencia’ sweet orange. The treatment experiment. old at the time of herbicide application. detailispresentedinTables5and6.
608 • October 2011 21(5) Table 3. Effects of herbicide treatments on control of texas panicum at 15, 30, Pendimethalin is used as a preemer- 45, 60, and 90 d after treatment (DAT) at Frostproof, FL, in 2009. gence herbicide for control of grass and 15 DAT 30 DAT 45 DAT 60 DAT 90 DAT small-seeded dicot weed species; how- Herbicide treatmentz % controly ever, it can be tank mixed with other herbicide(s) to improve efficacy (BASF Untreated control 0 c 0 d 0 d 0 d 0 c Corp., 2009). In the treatments that Glyphosate 1.5 lb/acre 76 a 79 ab 77 b 75 b 20 b included pendimethalin as a tank mix Saflufenacil 1 oz/acre 30 b 43 c 7 c 3 c 0 c partner, control of grass weeds was Saflufenacil 1 oz/acre + 78 a 76 b 75 b 77 b 28 b comparable with a tank mix of glyph- glyphosate 1.5 lb/acre osate, norflurazon, and diuron at 15, Saflufenacil 2 oz/acre 30 b 42 c 8 c 7 c 7 c 30, 60, and 90 DAT (Table 1). Similar Saflufenacil 2 oz/acre + 81 a 76 b 80 b 78 b 33 b to this result, a tank mix of pendime- glyphosate 1.5 lb/acre thalin and glyphosate provided 95% Saflufenacil 3 oz/acre 16 b 35 c 12 c 7 c 10 bc control of witchgrass (Panicum capil- Saflufenacil 3 oz/acre + 85 a 81 a 77 b 77 b 32 b lare) and yellow foxtail (Setaria pum- glyphosate 1.5 lb/acre ila) compared with glyphosate applied Saflufenacil 2 oz/acre + 89 a 86 a 90 a 88 a 88 a alone at 45 DAT in glyphosate-resistant glyphosate 1.5 lb/acre + alfalfa (Medicago sativa) (Affeldt and pendimethalin 112 oz/acre Rice, 2008). Saflufenacil 3 oz/acre + 88 a 88 a 90 a 88 a 83 a The major broadleaf weeds in- glyphosate 1.5 lb/acre + festing the Expt. 1 at Polk City, FL, pendimethalin 112 oz/acre were florida/brazil pusley (Richardia Saflufenacil 1 oz/acre + 88 a 85 a 93 a 85 a 85 a spp.), dayflower, and black nightshade glyphosate 0.75 lb/acre + (Solanum nigrum). The visual control pendimethalin 112 oz/acre ratings were combined for all the broad- zAll herbicide treatments included ammonium sulfate at 2.03 kg/100 L (16.941 lb/100 gal) solution and leaf species and presented as total broad- methylated seed oil applied at 1% v/v; 1 lb/acre = 1.1209 kgÁha–1, 1 oz/acre = 70.0532 gÁha–1. yThe data were arcsine transformed for homogenous variance before analysis; however, data presented here are the leaf species controlled. Compared with means of actual values for comparison. Least square means within columns with no common letters are significantly untreated control, all the treatments different according to Fisher’s protected least significant difference test where P < 0.05. were significantly effective for control- ling broadleaf weeds at 15, 30, 60, and 90 DAT (Table 1). Although the Herbicide applications were made on presented with mean separation based difference was nonsignificant with some 28 Apr. 2009 as explained in previous on transformed data. other treatments, maximum control of study. The nonionic surfactant (In- broadleaf weeds (82%) was obtained duce at 0.25% v/v) and ammonium Results and discussion with grower’s practice of using a tank sulfate at 2.03 kg/100 L solution were 2008. The predominant grass mix of norflurazon, diuron, and glyp- included in herbicide treatments. The species at the Polk City, FL, in Expt. hosate at 7 DAT. On the other hand, sweet orange trees were 3 years old at 1 included texas panicum (Panicum a tank mix of saflufenacil, glyphosate, the time of herbicide application. Her- texanum) and guineagrass (Panicum and pendimethalin was as effective bicide applications were made using a maximum). The visual control ratings as a tank mix of norflurazon, diuron, tractor mounted sprayer as explained were combined for all the grass species and glyphosate at 30, 60, and 90 in previous experiment. The visual per- and presented as total grass species DAT (Table 1). In an experiment cent control of weed species and po- controlled. Compared with untreated conducted for weed control in glyph- tential injury on citrus was evaluated at control, all the treatments were signifi- osate-resistant alfalfa, a tank mix of 14, 28, 42, and 86 DAT on the basis of cantly effective for controlling grass pendimethalin and glyphosate pro- the procedure explained in previous weeds at 7, 15, 30, 60, and 90 DAT vided 100% control of horseweed experiments. (Table 1). The application of glypho- compared with a tank mix of pendi- STATISTICAL ANALYSIS. The data sate alone provided significantly higher methalin with imazamox (25% con- from each field experiment was ana- grass weed control compared with saflu- trol) or 2,4-DB (45% control) at 45 lyzed separately. All data were sub- fenacil applied alone at 15, 60, and 90 DAT (Affeldt and Rice, 2008). Glyph- jected to analysis of variance (ANOVA), DAT. Later in the season, the tank osate tank mixed with pendimethalin and means were separated using Fish- mix treatments were superior com- provided long-term control of grass er’s protected least significant differ- pared with glyphosate or saflufenacil weeds; however, addition of saflufe- ence (LSD) test (P = 0.05) in SAS applied alone for controlling grass nacil provided better broadleaf weed (version 9.2; SAS Institute, Cary, NC). weeds. Among tank mixes, percent control. The tank mix of pendimethalin When the ANOVA revealed no sig- control of grass weeds declined after at all the rates was equally effective. nificant treatment-by-location inter- 30 DAT where pendimethalin was Grass and broadleaf weed species action for the Hanes and Dundee not included in the tank mix. For ex- present in Expt. 2 at Polk City, FL, experimental sites in 2008, data were ample, saflufenacil applied alone or were the same as in Expt. 1 in 2008. pooled over locations for analysis. The in a combination with glyphosate was All treatments were effective for reduc- data of percent weed control were arc- less effective than a tank mix of saflu- ing grass weed populations compared sine transformed before analysis; how- fenacil, glyphosate, and pendimetha- with untreated control (Table 2). A ever, nontransformed percentages are lin at 60 and 90 DAT (Table 1). tank mix of saflufenacil with glyphosate
• October 2011 21(5) 609 RESEARCH REPORTS
and pendimethalin provided 82% con- trol of grass weeds at 7 DAT; how- ever, it was not significantly different Cutleaf evening primrose from other tank mix treatments. Per- cent control of grass weeds increased gradually with all herbicide treatments
y at 30 DAT, and thereafter control was
eatment (DAT) at reduced slightly with the treatments . –1 where pendimethalin was not added ha Á in the tank mix. The application of 90 DAT glyphosate alone provided significantly higher percent control of grass weeds compared with saflufenacil applied alone at 30, 60, and 90 DAT (Table 2). This
pusley Spanishneedles might be due to the mode of action of
, 1 oz/acre = 70.0532 g saflufenacil as it is primarily a dicot her- –1 Florida/brazil bicide; therefore, it is not much effec- ha Á tive on monocot species (BASF Corp., 2010c). For example, experiments conducted to evaluate winter wheat 1.1209 kg Cutleaf evening
primrose (Triticum aestivum) response to post- emergence application of saflufenacil east square means within columns with no common letters are significantly different suggested that wheat foliar necrosis was <15% at 10 to 20 DAT and was y not evident at 30 DAT (Frihauf et al., 2010). A tank mix of saflufenacil and glyphosate provided similar control 30 DAT % control of grass weeds compared with a tank mix of saflufenacil, glyphosate, and pendimethalin at 30 DAT. However, a tank mix of saflufenacil with glyph- osate provided inferior grass control pusley Spanishneedles compared with a tank mix of saflufe-
Florida/brazil nacil, glyphosate, and pendimethalin at 60 and 90 DAT (Table 2). There- fore, addition of pendimethalin was very effective to provide residual grass
Cutleaf weed control. evening primrose All herbicide treatments were ef- fective for controlling broadleaf weeds in all the visual ratings compared with
y untreated control (Table 2). Percent
0.05. control of broadleaf weeds was similar
< when glyphosate or saflufenacil was ap- P
15 DAT plied alone. A tank mix of saflufenacil with glyphosate provided significantly better control of broadleaf weeds com- pared with saflufenacil applied alone at 15, 30, 60, and 90 DAT. At 15 and 30 83 b86 ab 94 ab90 a 9489 ab a 88 a86 ab 95 ab 89 a 63 cd 98 a81 bc 91 a 66 99 c a 91 a 78 b 89 bc 73 b 94 a 78 b 81 a 89 a 84 b 80 81 a b 90 a 53 cd 76 ab 90 a 89 a 58 c 85 ab 48 a 93 80 a b 68 b 95 a 63 a 75 78 ab a 91 a 73 ab 57 ab 75 a 77 a 58 ab 77 a 65 a 82 a 57 ab 82 a 83 a pusley Spanishneedles DAT, a tank mix of saflufenacil, glyph- osate, and pendimethalin and a tank Florida/brazil mix of glyphosate and pendimethalin provided similar control of broadleaf weeds compared with a tank mix of saflufenacil and glyphosate. Control of z broadleaf weeds reduced gradually af- ter 30 DAT in the treatments where pendimethalin was not included in a tank mix. For example, at 60 and 90 DAT, significantly higher control of broadleaf weeds was obtained in the
glyphosate 60 oz/acre glyphosate 60 oz/acre glyphosate 2.7 lb/acre glyphosate 60 oz/acre + pendimethalin 112 oz/acre glyphosate 60 oz/acre + pendimethalin 112 oz/acre glyphosate 60 oz/acre + pendimethalin 112 oz/acre treatments where pendimethalin was All herbicide treatments included ammonium sulfate at 2.03 kg/100 L (16.941 lb/100 gal) solution and methylated seed oil applied at 1% v/v; 1 lb/acre = Data were arcsine transformed for homogenous variance before analysis; however, data presented here are the means of actual values for comparison. L Frostproof, FL, in 2009. Herbicide treatment Table 4. Effects of herbicide treatments on control of florida/brazil pusley, spanishneedles, and cutleaf evening primrose at 15, 30, and 90 d after tr z y according to Fisher’s protected least significant difference test where Untreated controlGlyphosate 60 oz/acreSaflufenacil 1 oz/acreSaflufenacil 1 oz/acre + Saflufenacil 2 oz/acreSaflufenacil 2 oz/acre 75 + c 0 dSaflufenacil 78 3 bc oz/acreSaflufenacil 3 oz/acre + Saflufenacil 79 2 b oz/acre + 89 bc 88 c 0 dSaflufenacil 84 3 b oz/acre + 79 b 95 abSaflufenacil 81 1 b oz/acre + 0 c 91 bc 70 b 83 b 60 d 0 e 87 abtankmixedwithglyphosateorwith 58 d 85 ab 69 cd 60 d 0 e 90 a 66 d 78 b 75 bc 53 0 cd c 71 c 53 cd 80 b 0 55 62 e cd a 30 c 45 d 75 a 40 b 0 d 62 a 43 bc 77 a 0 b 73 a
610 • October 2011 21(5) Table 5. Effects of herbicide treatments on control of florida/brazil pusley, common purslane, and dogfennel at 14, 42, and 86 d after treatment (DAT) at Lake Alfred, FL, in 2009. 14 DATy 42 DATy 86 DATy Florida/ Florida/ Florida/ brazil Common brazil Common brazil Common pusley purslane Dogfennel pusley purslane Dogfennel pusley purslane Dogfennel Herbicide treatmentz % control Untreated control 0 c 0 d 0 e 0 f 0 d 0 e 0 f 0 d 0 f Saflufenacil 1 oz/acre 55 ab 78 c 73 bc 44 e 71 c 75 d 46 e 73 c 68 e Saflufenacil 1 oz/acre + 61 ab 93 ab 89 a 71 cd 78 abc 83 abc 56 de 76 abc 73 de glyphosate 40 oz/acre Saflufenacil 1 oz/acre + 59 ab 93 ab 64 c 74 bcd 80 abc 81 bcd 65 bcd 76 abc 79 bc pendimethalin 112 oz/acre Glufosinate 35 oz/acre 70 a 94 ab 80 ab 75 abcd 74 bc 80 cd 64 cd 76 abc 75 cd Paraquat 1 lb/acre 65 a 99 a 89 a 81 ab 85 a 89 a 76 ab 81 ab 81 ab Glyphosate 40 oz/acre 54 ab 91 ab 81 ab 79 abc 84 a 84 abc 65 bcd 76 abc 76 bcd Glyphosate 60 oz/acre 69 a 94 ab 80 ab 78 abcd 85 a 85 abc 73 abc 75 bc 79 bc Trifloxysulfuron-sodium 43 b 83 bc 84 ab 78 abcd 73 bc 83 abc 73 abc 80 ab 81 ab 0.4 oz/acre Glyphosate 40 oz/acre + 51 ab 94 ab 71 bc 69 d 80 abc 84 abc 71 abc 79 abc 81 ab trifloxysulfuron-sodium 0.2 oz/acre Glyphosate 40 oz/acre + 65 a 91 ab 83 ab 76 abcd 80 abc 88 ab 71 abc 79 abc 79 bc trifloxysulfuron-sodium 0.4 oz/acre Glyphosate 40 oz/acre + 58 ab 94 ab 85 ab 80 abc 85 a 86 abc 68 abcd 79 abc 78 bcd simazine 1 lb/acre Glyphosate 40 oz/acre + 64 ab 93 ab 81 ab 84 a 81 ab 88 ab 78 a 83 a 85 a simazine 1 lb/acre + mesotrione 3 oz/acre Glyphosate 40 oz/acre + 65 a 95 ab 73 bc 80 abc 76 abc 88 ab 69 abc 76 abc 79 bc norflurazon 3.2 lb/acre zAll herbicide treatments included ammonium sulfate at 2.03 kg/100 L (16.941 lb/100 gal) solution and nonionic surfactant applied at 0.25% v/v; 1 lb/acre = 1.1209 kgÁha–1, 1 oz/acre = 70.0532 gÁha–1. yThe data were arcsine transformed for homogenous variance before analysis; however, data presented here are the means of actual values for comparison. Least square means within columns with no common letters are significantly different according to Fisher’s protected least significant difference test where P < 0.05. saflufenacil and glyphosate compared application of saflufenacil applied at weeds, but provided similar broadleaf with the tank mix of saflufenacil plus 2 or 4 oz/acre on citrus trees at 7, 15, weed control compared with glyph- glyphosate (Table 2). This might be and 30 DAT (data not shown). The osate applied alone; however, a tank because pendimethalin is primarily a label rate of saflufenacil in citrus is 1 mix of saflufenacil with glyphosate usu- residual grass herbicide; however, ex- oz/acre, so citrus trees have provided ally increased weed control efficacy. cellent broadleaf weed control with 2- to 4-fold safety. This study dem- Addition of pendimethalin into the addition of pendimethalin in the tank onstrated that saflufenacil with adju- tank mix of saflufenacil and glyphosate mix indicates synergistic effect of other vants used in this study can be a good improved weed control by providing two herbicides on the efficacy of pen- option for broadleaf weed control in a longer residual activity similar to a dimethalin. A previous study suggested citrus groves without any injury on cit- tank mix of norflurazon, diuron, and that saflufenacil with crop oil concen- rus trees (data not shown). By contrast, glyphosate. There was no difference trate and saflufenacil tank mixed with experiments conducted to determine in control of grass and broadleaf weeds 2,4-D amine controlled blue mustard the response of maize to postemer- with the high rate of pendimethalin as (Chorispora tenella) ‡91% at 17 and 21 gence application of saflufenacil sug- a tank mix partner. Therefore, a lower DAT compared with less than 50% gested that addition of an adjuvant rate of pendimethalin should be used control with 2,4-D amine applied alone to saflufenacil caused 99% injury at whenappliedinatankmixwith (Frihauf et al., 2010). three leaf stage and reduced yield up saflufenacil and glyphosate to achieve There was no treatment by loca- to 59% compared with saflufenacil ap- sufficient weed control. There was no tion interaction for the Hanes City, plied without adjuvant (Soltani et al., injury from any saflufenacil treatment FL, and Dundee, FL, experimental 2009). applied alone even at higher rates up sites to evaluate the injury of saflufe- Overall results of the experi- to 4 oz/acre or in a tank mix with nacil in citrus; therefore data were ments conducted in 2008 suggested glyphosate or in a sequential applica- pooled over locations for analysis. There that application of saflufenacil alone tion on citrus trees indicating its level was no injury from a single or sequential was not effective for controlling grass of safety (data not shown).
• October 2011 21(5) 611 RESEARCH REPORTS
2009. The only grass weed pres- ent at the Frostproof, FL, experimen- tal site was texas panicum. Visual weed ragweed Common control evaluations conducted at dif- ferent time intervals suggested that all herbicide treatments were effective for y
ake Alfred, FL, controlling texas panicum compared .
–1 with untreated control (Table 4). A ha Á tank mix of saflufenacil with glypho- 86 DAT sate provided a greater control of texas panicum compared with saflufenacil applied alone. For example, control at 45, 60, and 90 DAT was 7%, 3%, and 0%, respectively, whereas a tank mix
Spiny of glyphosate with saflufenacil pro- , 1 oz/acre = 70.0532 g amaranth Spanishneedles –1 vided 75%, 77%, and 28% control, ha Á respectively (Table 3). The residual weed control of saflufenacil and glyp- hosate treatments started declining
ragweed beyond 45 DAT. Later in the season Common
cre = 1.1209 kg (>30 DAT), a tank mix of saflufenacil,
n. Least square means within columns with no common letters are significantly glyphosate, and pendimethalin pro-
y vided significantly better control of texas panicum compared with other treatments. Control of texas panicum 42 DAT % control was >82% at 90 DAT in a tank mix of saflufenacil, glyphosate, and pendime- thalin indicated the effectiveness of pen- dimethalin as a tank mix partner (Table 3). Thus, this tank mix combination
Spiny can provide a long-term weed control
amaranth Spanishneedles option to citrus growers. The major broadleaf weeds at the Frostproof, FL, experimental site were florida/brazil pusley, spanishneedles (Bidens bipinnata), and cutleaf even- ragweed Common ing primrose (Oenothera laciniata). All herbicide treatments were effective for controlling broadleaf weeds com- y pared with untreated control (Table 4).
0.05. The application of saflufenacil alone <
P at 1 oz/acre provided similar control 14 DAT of florida/brazil pusley compared with a tank mix of saflufenacil and glyph- osate at 15 and 30 DAT (Table 4). Knezevic et al. (2009) reported that saflufenacil applied at 1 to 2 oz/acre Spiny 89 abc 95 a 74 abc 90 ab 89 a 89 a 81 bc 79 a 65 e 81 bc 89 a 65 c 86 abc 81 b 80 bc 85 ab 83 a 76 bcd 93 a 91 a 79 abc 90 ab 84 ab 80 bc 83 bc 81 a 81 abc 90 ab 95 a 80 abc 85 bc 85 ab 81 bc 85 ab 83 a 79 abcd 91 ab 93 a 88 ab 80 c 90 a 79 bc 83 bc 83 a 84 ab 93 a 94 a 78 abc 86 abc 84 ab 80 bc 89 a 86 a 85 a 88 abc 89 awas sufficient 81 abc to 93 a control broadleaf 81 b weeds 78 c 83 bc 83 a 81 abc amaranth Spanishneedles including field bindweed (Convolvulus arvensis), prickly lettuce (Lactuca ser- riola), henbit (Lamium amplexicaule), shepherd’s-purse, dandelion (Tarax- acum officinale),andfieldpennycress (Thlaspi arvense). Control of spanish- needles and cutleaf evening primrose z was significantly better in a tank mix treatments at 15 and 30 DAT com- pared with saflufenacil applied alone (Table 4). A tank mix of pendimethalin, saflufenacil, and glyphosate provided 81% to 99% control of all three broad- glyphosate 40 oz/acre pendimethalin 112 oz/acre trifloxysulfuron-sodium 0.2 oz/acre trifloxysulfuron-sodium 0.4 oz/acre simazine 1 lb/acre 1 lb/acre + mesotrione 3 oz/acre norflurazon 3.2 lb/acre leaf weeds at 15 DAT. The tank mix All herbicide treatments included ammonium sulfate at 2.03 kg/100 L (16.941 lb/100 gal) solution and nonionic surfactant applied at 0.25% v/v; 1 lb/a The data were arcsine transformed for homogenous variance before analysis; however, data presented here are the means of actual values for compariso in 2009. Herbicide treatment Table 6. Effects of herbicide treatments on control of spiny amaranth, spanishneedles, and common ragweed at 14, 42, and 86 d after treatment (DAT) at L z y different according to Fisher’s protected least significant difference test where Untreated controlSaflufenacil 1 oz/acreSaflufenacil 1 oz/acre + 84 abc 0 d 90 a 0 c 68 c 0 d 84 bc 0 d 84 ab 0 c 78 c 79 c 0 d 0 69 d b 38 f 0 c 0 g Saflufenacil 1 oz/acre + Glufosinate 35 oz/acreParaquat 1 lb/acreGlyphosate 40 oz/acreGlyphosate 60 oz/acreTrifloxysulfuron-sodium 0.4 oz/acreGlyphosate 40 oz/acre + 79 c 84 abc 89 abc 90 ab 94 a 95 79 a b 96 a 95 a 94 a 72 90 bc a 80 abc 88 88 ab ab 88 ab 86 ab 88 ab 85 bc 85 bc 88 ab 85 ab 84 ab 89 a 85 85 ab ab 78 c 89 a 85 ab 80 bc 83 81 bc bc 83 bc 83 bc 80 bc 84 a 81 a 80 a 84 a 81 80 a abc 78 abcd 75 cd 79 abcd 73 de Glyphosate 40 oz/acre + Glyphosate 40 oz/acre + Glyphosate 40 oz/acre + simazine Glyphosate 40 oz/acre + treatment that included pendimethalin
612 • October 2011 21(5) controlled 76% to 95% broadleaf weeds Alfred, FL, included florida/brazil from 79% to 95% compared with the at 30 DAT. Control of florida/brazil pusley, spanishneedles, common purs- untreated control (Table 6). Simi- pusley and spanishneedles started de- lane (Portulaca oleracea), dogfennel larly, all the herbicide treatments pro- clining at 45 DAT (data not shown) (Eupatorium capillifolium), spiny am- vided >79% control of spanishneedles and was minimal at 90 DAT when aranth (Amaranthus spinosus), and com- up to 42 DAT. However, control of glyphosate or saflufenacil applied alone mon ragweed (Ambrosia artemisiifolia). spanishneedles treated with saflufena- or in a tank mix (Table 4). A tank mix Results showed that all herbicide treat- cil alone declined to 69% at 86 DAT of saflufenacil, glyphosate, and pendi- ments provided significant control of compared with other treatments (Ta- methalin provided long-term residual broadleaf weeds compared with un- ble 6). Surprisingly, control of com- weed control. For example, control of treated control (Tables 5 and 6). A mon ragweed was relatively less in a florida/brazil pusley was >72% at 90 tank mix of saflufenacil with pendi- tank mix of saflufenacil with pendi- DAT when pendimethalin was a tank methalin provided 59%, 93%, and 65% methalin at 14 DAT; however, later in mix partner. Although there was no control of florida/brazil pusley, purs- the season, control of common rag- significant difference with other tank lane, and dogfennel, respectively, at 14 weed improved in this treatment and mix treatments, control of cutleaf even- DAT. Similarly, saflufenacil alone and provided >76% control at 42 and 86 ing primrose was >80% at 90 DAT with saflufenacil plus glyphosate provided DAT (Table 6). The efficacy of saflu- pendimethalin as a tank mix partner similar control of these broadleaf weed fenacil applied alone declined by 86 (Table 4). There was no injury on grape- species at 28 DAT (data not shown). A DAT, and common ragweed control fruit from any of the treatments. previous study reported that saflufena- declined to 38% (Table 6). Other her- The only grass weed infesting the cil applied at 30 gÁha–1 (0.43 oz/acre) bicide treatments provided 65% to experimental site at Lake Alfred, FL, reduced the density of blue mustard, 85% common ragweed control at 86 in 2009 was guineagrass. Saflufenacil flixweed (Descurainia sophia), palmer DAT. The highest control of broad- applied alone provided only 5% to 40% amaranth (Amaranthus palmeri), and leaf species was obtained in a tank mix control of guineagrass (data not shown). tumble pigweed (Amaranthus albus) of saflufenacil with glyphosate and A tank mix of saflufenacil with glyph- by 63% to 93% (Geier et al., 2009). A pendimethalin, and it was usually com- osate provided 88% and 84% control tank mix of pendimethalin and saflu- parable with a tank mix of glyphosate of guineagrass, respectively, at 14 and fenacil had 68% to 86% control of plus simazine, glyphosate plus sima- 28 DAT, whereas a tank mixes of broadleaf weeds at 28 DAT. The re- zine plus mesotrione, and glyphosate saflufenacil with pendimethalin pro- duced weed control in this treatment plus norflurazon (Table 6). Weed spe- vided relatively less control of guinea- combination might be due to the weeds cies that are not effectively controlled grass at 14 and 28 DAT. Similarly, already present at the experimental site by a single herbicide have shown in- glufosinate and paraquat applied alone before herbicide applications. Similarly, creased occurrence in citrus groves and provided 70% and 65% control of broadleaf weed control with glufosinate can be better controlled with a tank guineagrass, respectively, at 14 DAT; and paraquat varied from 65% to 99% mix of herbicides. For example, a tank however, the control was reduced to at 14 and 28 DAT (Table 5). The mix of glyphosate plus carfentrazone 58% at 86 DAT (data not shown). broadleaf weed control by glufosinate provided better control of florida/bra- Glyphosate applied alone at higher rate and paraquat applied alone was com- zil pusley and dayflower compared with provided 90% guineagrass control at 14 parable to glyphosate and saflufenacil applied alone (Sharma et al., 2008). DAT compared with 60% control at 86 treatments. Similarly, trifloxysulfuron With the exception of trifloxy- DAT (data not shown). Similarly, a tank applied alone or tank mixed with glyp- sulfuron-sodium, there was no injury mix of trifloxysulfuron with glyphosate hosate provided 43% to 65% control of any herbicide treatment on ‘Valen- provided 74% to 90% control of guinea- of florida/brazil pusley at 14 DAT; cia’ sweet orange trees (data not shown). grass compared with 48% to 66% con- however, florida/brazil pusley con- The application of trifloxysulfuron- trol by trifloxysulfuron alone. A tank trol was improved at 28 DAT (60% sodium at higher rate caused some ini- mix of glyphosate with simazine pro- to 73%) (data not shown) with tri- tial injury to citrus trees (5% to 9%) vided 60% to 90% control of guinea- floxysulfuron alone or in a tank mix (data not shown). However, those trees grass, and there was no additional with glyphosate (Table 5). The per- recovered later in the season, and no control provided by addition of meso- cent control of florida/brazil pusley injury symptom was noticed at 86 trione in this treatment combination. and dogfennel was 71% and 81%, DAT. Trifloxysulfuron-sodium is an When glyphosate was tank mixed with respectively, with trifloxysulfuron ap- acetolactate synthase inhibitor and be- norflurazone, a consistent control plied alone or in a tank mix with glyp- longs to the sulfonylurea group, which of guineagrass (‡80%) was observed hosate at 86 DAT. A study conducted hasbeenevaluatedforweedcontrol throughout the growing season (data to evaluate the effects of trifloxysul- in cotton (Porterfield et al., 2003) and not shown). The residual control of furon on 12 weed species of citrus sugarcane (Saccharum officinarum) saflufenacil and other herbicides applied demonstrated various responses of (Dally and Richard, 2008). Similar to alone or in a tank mix with glyphosate weeds to this herbicide (Singh and this result, previous studies reported that usually reduced efficacy beyond 56 Singh, 2004). The differential control cotton recovered from trifloxysulfuron DAT. Similarly, guineagrass control by trifloxysulfuron-sodium could be injury within 3 to 6 weeks after treat- with postemergence herbicides such as attributed to differences in uptake, ment and caused no yield penalty (Barber glufosinate and paraquat started declin- translocation, and metabolism in dif- et al., 2002; Porterfield et al., 2003). ing beyond 56 DAT (data not shown). ferent species (Askew and Wilcut, 2002). Overall results of experiments The major broadleaf weeds in- All herbicide treatments provided conductedin2009suggestedthata festing the experimental site at Lake good control of spiny amaranth ranging tank mix of saflufenacil, glyphosate, and
• October 2011 21(5) 613 RESEARCH REPORTS pendimethalin provided similar weed Askew, S.D. and J.W. Wilcut. 2002. Ab- Futch, S.H. and M. Singh. 2007. Weeds control compared with several other sorption, translocation and metabolism in Florida citrus—New challenges and tank mix herbicides including a tank of foliar-applied CGA-362622 in cotton, opportunities. Citrus Ind. 88:15–17. peanut, and selected weeds. Weed Sci. mix of glyphosate and simazine, glyp- Futch, S.H. and M. Singh. 2010. Florida cit- 50:293–298. hosate plus simazine plus mesotrione, rus pest management guide: Weeds, p. 125– and glyphosate with norflurazon. There- Barber, L.T., D.B. Reynolds, J.C. 137. In: M.E. Rogers, M.M. Dewdney, fore, a tank mix herbicides with different Sanders, D.G. Wilson, N.W. Buehring, and T.M. Spann (eds.). 2010 Florida cit- mode of action will control problem and K.M. Bloodworth. 2002. Weed con- rus pest management guide. Inst. Food weed species including herbicide-re- trol with CGA-362622 in roundup ready Arg. Sci., Univ. of Florida, Gainesville. sistant weeds. Saflufenacil has been re- and BXN cotton systems. Proc. Southern Geier, P.W., P.W. Stahlman, and L.D. ported to be effective in controlling Weed Sci. Soc. 55:140. (Abstr.). Charvat. 2009. Dose responses of five glyphosate-resistant weeds (Ashigh and BASF Corp. 2008. KixorTM herbicide broadleaf weeds to saflufenacil. Weed Hall, 2010) such as glyphosate-resistant worldwide. Worldwide technical bro- Technol. 23:313–316. horseweed (Owen et al., 2011). Pre- chure. BASF Corp., Research Triangle Green, J.M. 1991. Maximizing herbicide liminary experiments conducted in Park, NC. efficiency with mixtures and expert sys- California confirmed that saflufenacil BASF Corp. 2009. Prowl H OTM herbi- tems. Weed Technol. 5:894–897. is a strong performer on several win- 2 cide label. BASF Corp., Research Triangle Grossman,K.,R.Niggeweg,N.Christiansen, ter annual broadleaf weeds, including Park, NC. glyphosate-resistant horseweed and hairy R. Looser, and T. Ehrhardt. 2010. The TM herbicide saflufenacil (KixorTM) is a new fleabane (Conyza bonariensis)inpe- BASF Corp. 2010a. Optil herbicide label. BASF Corp., Research Triangle inhibitor of protoporphyrinogen IX oxi- rennial crops (B. Hanson, personal dase activity. Weed Sci. 58:1–9. communication). Park, NC. BASF Corp. 2010b. SharpenTM herbicide Heap, I. 2011. International survey of label. BASF Corp., Research Triangle herbicide resistant weeds. 5 May 2011. Conclusion Park, NC.
614 • October 2011 21(5) Sharma, S.D. and M. Singh. 2007. Effect of Spreen, T.H., R.E. Barber, M.G. Brown, 2011.
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