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Spring Applied Burndown Options for Control of Glyphosate-resistant Horseweed. T.W. Eubank D.H. Poston, V.K. Nandula, D.B. Reynolds, D.R. Shaw, H.R. Robinson, J.B. Blessitt, R.T. Coleman, and T. Evans. Horseweed ( Conyza canadensis ). Horseweed Emergence vs Temp 1. Eubank, 2006.
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Spring Applied Burndown Options for Control of Glyphosate-resistant Horseweed T.W. Eubank D.H. Poston, V.K. Nandula, D.B. Reynolds, D.R. Shaw, H.R. Robinson, J.B. Blessitt, R.T. Coleman, and T. Evans
Horseweed Emergence vs Temp1 Eubank, 2006 1Averaged 3 locations 2003-2005
Introduction • Horseweed has been documented to be resistant to many herbicide modes of action across the U.S. including, • Glyphosate • Paraquat • ALS Inhibitors • Triazines • Ureas Heap, 2005
Introduction • The widespread adoption of glyphosate-resistant crops and the advent of glyphosate-resistant horseweed (Conyza canadensis (L.) Cronq.) has created a need for research investigating alternative measures of control for this troublesome weed.
Introduction • Determining the most efficacious chemical means for controlling horseweed is imperative in reducing possible crop yield losses due to competition.
Objectives • Determine the most effective chemical burndown options for emerged horseweed populations. • Evaluate the impact of various burndown herbicides on horseweed populations.
Chemical ControlMaterials and Methods • RCB, 4 replications • Plots: 10 x 40 ft • Tractor mounted sprayer @ 15 gal/acre • Applied April 5, 2005 and March 15, 2006 • Horseweed: 4 – 6 in tall
Chemical ControlMaterials and Methods • Burndown treatments alone/+ tank-mix • Roundup WeatherMax @ 0.77 lb ae/a • Gramoxone Inteon @ 0.75 ai/a • Ignite 280 @ 0.42 lb ai/a • Burndown treatments alone • Roundup WeatherMax @ 1.12 lb ae/a • Gramoxone Inteon @ 0.88 ai/a • Ignite 280 @ 0.53 lb ai/a
Chemical ControlMaterials and Methods • Tank-mixed herbicide treatments • 2,4-D @ 0.75 lb ae/a • Clarity @ 0.25 lb ai/a • Valor @ 0.064 lb ai/a • Cotoran @ 0.5 lb ai/a • Caparol @ 1 lb ai/a • Harmony XP @ 0.0234 lb ai/a • Clarity + Valor @ 0.25 + 0.064 lb ai/a • Untreated
Chemical ControlMaterials and Methods • All data analyzed in SAS with the PROC GLM procedure • Means separated using Fisher’s protected LSD test (p = 0.05)
Horseweed Control with WeatherMax Based Burndown1 1 Treatments shown based on 4 WAT. Horseweed 4-6 in tall. WeatherMax @ 0.77 lbs ae/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 8
Horseweed Populations with WeatherMax Based Burndown1 1 Horseweed plants/m2 at 6 WAT. WeatherMax @ 0.77 lb ae/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 41
Horseweed Controlwith Inteon Based Burndown1 1 Treatments shown based on 4 WAT. Horseweed 4-6 in tall. Inteon @ 0.75 lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 8
Horseweed Populations with Inteon Based Burndown1 1 Horseweed plants/m2 at 6 WAT. Inteon @ 0.75 lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 39
Horseweed Control with Ignite Based Burndown1 1 Treatments shown based on 4 WAT. Horseweed 4-6 in tall. Ignite @ 0.42 lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 5
Horseweed Populations with Ignite Based Burndown1 1 Horseweed plants/m2 at 6 WAT. Ignite @ 0.42 lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 14
Conclusions • WeatherMax alone provided only 63 – 73% control of horseweed 4 WAT. • The addition of 2,4-D or Clarity improved WeatherMax control to greater than 90% and reduced horseweed populations by 99% compared to the untreated check.
Conclusions • Inteon alone treated plants quickly recovered and by 4 WAT provided only 55 – 60% control. • The addition of 2,4-D or Clarity to Inteon significantly improved control to 83%, however, horseweed populations were reduced by only 44% and 52%, respectively, when compared to the untreated.
Conclusions • Ignite applied alone provided better than 92% control of horseweed and all tank-mix treatments were generally better than 86%. • Horseweed populations were reduced by greater than 88% when Ignite was tank-mixed, while Ignite alone reduced populations only 65%.
Conclusions • New horseweed emergence, after burndown alone treatments, could be responsible for slight increase in horseweed populations as compared to burndown + tank-mix treatments.
V.K. Nandula R.T. Coleman J.B. Blessitt T.H. Gibson T.A. Evans H.R. Robinson E. Graves Special Thanks