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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
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Horseweed (Conyza canadensis)
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Horseweed Emergence vs Temp1
Eubank, 2006 1Averaged 3 locations
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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
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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.
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Introduction Determining the most efficacious chemical means for controlling horseweed is imperative in reducing possible crop yield losses due to competition.
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Objectives Determine the most effective chemical burndown options for emerged horseweed populations. Evaluate the impact of various burndown herbicides on horseweed populations.
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Chemical Control
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Chemical Control Materials and Methods
RCB, 4 replications Plots: 10 x 40 ft Tractor mounted 15 gal/acre Applied April 5, 2005 and March 15, 2006 Horseweed: 4 – 6 in tall
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Chemical Control Materials and Methods
Burndown treatments alone/+ tank-mix Roundup 0.77 lb ae/a Gramoxone 0.75 ai/a Ignite 0.42 lb ai/a Burndown treatments alone Roundup 1.12 lb ae/a Gramoxone 0.88 ai/a Ignite 0.53 lb ai/a
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Chemical Control Materials and Methods
Tank-mixed herbicide treatments lb ae/a lb ai/a lb ai/a 0.5 lb ai/a 1 lb ai/a Harmony lb ai/a Clarity lb ai/a Untreated
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Chemical Control Materials and Methods
All data analyzed in SAS with the PROC GLM procedure Means separated using Fisher’s protected LSD test (p = 0.05)
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Horseweed Control with WeatherMax Based Burndown1
1 Treatments shown based on 4 WAT. Horseweed 4-6 in tall lbs ae/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 8
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Horseweed Populations with WeatherMax Based Burndown1
1 Horseweed plants/m2 at 6 WAT lb ae/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 41
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Untreated 4 WAT
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WeatherMax 0.77 lb ae/a 2 WAT
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WeatherMax 0.77 lb ae/a 4 WAT
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Horseweed Control with Inteon Based Burndown1
1 Treatments shown based on 4 WAT. Horseweed 4-6 in tall lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 8
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Horseweed Populations with Inteon Based Burndown1
1 Horseweed plants/m2 at 6 WAT lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 39
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Inteon 0.75 lb ai/a 2 WAT
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Inteon 0.75 lb ai/a 4 WAT
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Horseweed Control with Ignite Based Burndown1
1 Treatments shown based on 4 WAT. Horseweed 4-6 in tall lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 5
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Horseweed Populations with Ignite Based Burndown1
1 Horseweed plants/m2 at 6 WAT lb ai/a with all tank mixes. Averaged from 2005 – 2006. LSD (0.05) = 14
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Ignite 0.42 lb ai/a 2 WAT
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Ignite 0.42 lb ai/a 4 WAT
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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.
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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.
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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%.
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Conclusions New horseweed emergence, after burndown alone treatments, could be responsible for slight increase in horseweed populations as compared to burndown + tank-mix treatments.
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Special Thanks V.K. Nandula R.T. Coleman J.B. Blessitt T.H. Gibson
T.A. Evans H.R. Robinson E. Graves
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Questions?
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