Outline. Students 4/11/2017. Weed Science Program Update. Students Perennial peanut Smutgrass Bermudagrass

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1 Weed Science Program Update Brent Sellers UF IFAS Range Cattle REC and Agronomy Department, Ona, FL April 11, 217 Outline Students Perennial peanut Smutgrass Bermudagrass Students Jose Dias PhD Student Olivia Zugay MS Student Logan Martin MS Student 1

2 Perennial peanut (Arachis glabrata) Tropical and subtropical rhizomatous perennial forage Strong tap root and a dense mat of stolons Single yellow or orange flower Native to Brazil Supplemental forage crop and commercial hay production Once established, highly persistent under wide range of management conditions Reproduces vegetatively due to minimal seed production Expensive to incorporate into existing forage by sprigging Previous Research Imazapic is the standard in perennial peanut 2,4 D & hexazinone Clethodim for grass weeds Weed Shifts Imazapic and 2,4 D have been used repeatedly Weeds tolerant to these herbicides are becoming increasingly problematic Spiderling Blackberry briars Hairy indigo 2

3 Objective Determine tolerance of perennial peanut to: Glyphosate (.125 to 2 lb ae/acre) Triclopyr (.6 to 1 lb ae/acre) Two Locations: Zolfo Springs ( UF Peace ; disturbed in 214) Ona (4 varieties; planted in 25) Materials & Methods Plot size: 5 by 5 ft Application made 14 days after clipping at a sprayer output of 3 GPA Visual estimations of crop injury recorded 7, 15, 3, & 6 DAT Biomass collected from center.25 m 2 of each plot 6 DAT Zolfo Springs Injury (Glyphosate) a a a b ab b b b bc c c b c c cd 3

4 Zolfo Springs Biomass (Glyphosate) 6 5 Biomass (g m -2 ) Glyphosate Glyphosate rate rate (lb ae/acre) (kg ha -1 ) Ona Injury Glyphosate 3 DAT Injury (%) Ecoturf Florigraze Ona 33 UF-Tito I 2 Values Florigraze:.9 Ona 33: 1. UF Tito: 1.2 Ecoturf: Glyphosate rate (lb (kg ae/acre) ha -1 ) Ona Injury & Biomass Glyphosate Response of perennial peanut varieties averaged over glyphosate rate at at Ona, FL Table 3-1. Response of perennial peanut varieties averaged over glyphosate rate at Ona, in Ona, 216 FL FL, in in a. Injury Biomass Variety 15 DAT 3 DAT 6 DAT Peanut Weed (% injury) (g/m 2 ) Ecoturf 13 a 11 c 13 a 221 a 8 b Florigraze 13 a 17 a 13 a 93 b 147 a Ona a 15 ab 14 a 28 a 43 b UF-Tito 12 a 13 bc 11 a 235 a 46 b a Means followed by the same letter within columns are not significantly different at P.5. 4

5 Ona Biomass Glyphosate 25 Perennial peanut Broadleaf weeds 2 Biomass (g m -2 ) Glyphosate rate rate (lb(kg ae/acre) ha -1 ) Ona Biomass Ratio Glyphosate 5.5 Perennial peanut:weed biomass ratio Glyphosate rate rate (lb (kg ae/acre) ha -1 ) Zolfo Springs Injury (Triclopyr) Perennial peanut injury (%) DAT 3 DAT 6 DAT a a b b b b c c d d d d c c Triclopyr rate (lb ae/acre) a 5

6 Zolfo Springs Biomass (Triclopyr) Biomass (g m -2 ) Triclopyr Triclopyr rate (lb rate ae/acre) (kg ha -1 ) Ona Injury Triclopyr 3 DAT Injury (%) Ecoturf Florigraze Ona 33 UF-Tito I 2 Values UF Tito:.49 Florigraze:.66 Ona 33:.86 Ecoturf: Triclopyr Triclopyr rate rate (lb(kg ae/acre) ha -1 ) Ona Injury & Biomass Triclopyr Response of perennial peanut varieties averaged over triclopyr rate at Ona, FL in Table 3-2. Response of perennial peanut varieties averaged over triclopyr rate at Ona, FL 216 in 216 a. Injury Biomass Variety 15 DAT 3 DAT 6 DAT Peanut Weed (% injury) (g/m 2 ) Ecoturf 8 b 8 c 11 bc 27 ab 93 b Florigraze 11 b 12 b 15 a 95 c 155 a Ona b 9 bc 8 c 234 a 21 c UF-Tito 17 a 16 a 13 ab 199 b 48 c a Means followed by the same letter within columns are not significantly different at P.5. 6

7 Ona Biomass Triclopyr 25 Perennial peanut Broadleaf weeds 2 Biomass (g m -2 ) Triclopyr Triclopyr rate rate (lb ae/acre) (kg ha -1 ) Ona Biomass Ratio Triclopyr 5.5 Perennial peanut:weed biomass ratio Triclopyr Triclopyr rate rate (lb(kg ae/acre) ha -1 ) UF Peace Injury 3 DAT Untreated Glyphosate Triclopyr 7

8 Summary RPP relatively tolerant to glyphosate and triclopyr Glyphosate and triclopyr can be used for postemergence weed control if some injury can be tolerated Age of the stand will likely impact tolerance 23 Smutgrass (Sporobulus sp.) Serious perennial warm season grass weed Invasive, native to tropical Southeast Asia Beef Forage Range Practices Survey > top three Low preference (mature) with high seed production 24 8

9 Past Research Researchers have been studying smutgrass control since 195s Mechanical: Mowing Temporary solution / Spread Seeds Cultural: Grazing Too labor intensive Biological: Fungus Chemical: Hexazinone at 1 lb/acre during mid summer Good control, but 25 Challenges with Hexazinone Very expensive ( $4 5/A) whereas $8/A (2,4 D) or $18/A (Grazonnext + Pasturegard) Ranchers are forced to accept loses Will kill oak trees if you don t pay attention! Occasional lack of control / leaching or lack of incorporation. Xylem mobile Primarily absorbed by the roots Limited foliar absorption 26 Objectives 1) To determine the minimum amount of rainfall necessary for hexazinone incorporation within the root zone. 2) To determine the maximum amount of rainfall that can occur after hexazinone application, before it leaches below the smutgrass root zone. 27 9

10 Greenhouse Preliminary Study Conducted twice at the RCREC at Ona, in 216. Plants collected at site, stems separated and transplanted into pots. Soil was collected from the field at site and is classified as Placid Fine sand. 28 Aboveground dry weight 6 DAT First Run Aboveground fresh weight reduction (%) ED9 = 1.9 INCHES No rainfall Rainfall amount (in) 29 Aboveground dry weight at 3 DAT Second Run Aboveground dry weight reduction (%) ED9 = 2.4 INCHES No rainfall Rainfall amount (in) 3 1

11 Greenhouse Preliminary Study Results in.25 in.5 in 1. in 2. in 4. in 8. in 31 Field Study 32 Field Study Material & Methods An old bahiagrass pasture, but completely infested with giant smutgrass at present. ThesoilpresentattheresearchsiteisclassifiedasPlacid Fine sand, same used in the greenhouse trial

12 Field Study Material & Methods Factor Hexazinone rate Application timing Levels.5 and 1. lb ai/acre 19 weekly applications (started on April 22 th and ended on August 26 th ) Rainfall was recorded every week and then correlated with % visual control. 34 Field Study Material & Methods Visual % control at 3 DAT. Day of application 3 days after application 35 Field Preliminary Study Results Rainfall effects on hexazinone activity at 1 lb/a Control (%) Control (%) Rainfall (inches) Rainfall (inches) 36 12

13 Conclusions The rainfall amount after hexazinone application appears to significantly impact the efficiency of hexazinone on the control of giant smutgrass in south FL. Rainfall amounts between inches within the first seven days after application resulted in acceptable levels of control most of the time. 37 Future Research Additional rainfall studies (greenhouse and field) Impact of fire, grazing, and hexazinone Optimizing glyphosate & hexazinone rates using a roto wiper 38 Grass Weeds in Bermudagrass 13

14 Coastal Bermudagrass Tolerance to Glyphosate Biomass (lb/a) A B AB B B BC BC BC BC BC BC CD CD CD D Glyphosate rate (oz/a) 3 DAC 7 DAC 14 DAC Bermudagrass Response to Glyphosate Biomass (lb/a) A B AB BC C Glyphosate rate (oz/a) Bermudagrass Response to Glyphosate Biomass (lb/a) A AB B Time (DAC) 14

15 Future Research Bermudagrass cultivar response to glyphosate Jiggs and Coastal Visual injury, biomass, and quality Bahiagrass cultivar response to glyphosate Pensacola and Argentine Visual injury, reduction in stand, and regrowth Vaseygrass and guineagrass response to glyphosate, imazapic (Impose), and nicosulfuron + metsulfuron methyl (Pastora) under greenhouse & field conditions Visual injury, reduction in stand, and regrowth 15