Influence of Selected Herbicide Treatments on Ironweed Control, Forage Yield, and Forage Quality in Tall Fescue Pastures Kevin W. Bradley & Robert L. Kallenbach University of Missouri
Tall Ironweed (Vernonia altissima Nutt.) A perennial from a basal crown with stems that often persist throughout the winter Identified as one of the ten most common and troublesome weeds of pastures in Missouri Little is known about the effects of tall ironweed on forage yield or quality
Materials and Methods Trials established in tall fescue pastures with existing tall ironweed infestations Plots (10 x 45 ) arranged in a RCB design with 4 replications Herbicide applications made with CO 2 backpack sprayer delivering 15 gpa Weed control and crop injury visually rated throughout the growing season Tall ironweed stem counts taken 1 year after treatment (YAT)
Application Information Height Density Application Trial Stage (Inches) (# / m 2 ) Date 2004 Vegetative 7 84 May 19 2005 Vegetative 8 60 May 27
Materials and Methods: Forage Harvests & Quality Analysis Forage yields determined by harvesting the middle 5 x40 of each plot with HEGE forage harvester Samples from each plot ground and Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF), and crude protein content determined by Near Infrared (NIR) Spectroscopy (Pacific Scientific 5000 scanning monochromator)
Harvest Information Trial Harvest Date 2004 1 st Harvest 2 nd Harvest July 23 November 17 2005 1 st Harvest 2 nd Harvest July 22 November 18 *50 lbs N applied early Sep. each year
Materials and Methods: Herbicide Treatments Evaluated Trade Name Rate (Product / Acre) Active Ingredients Rate (lbs ai / Acre) 2, 4-D 1qt 2, 4-D 1.0 2, 4-D + Banvel 1 qt + 1 pt 2, 4-D + dicamba 1.0 + 0.5 Grazon P+D 1.5 pts picloram + 2, 4-D 0.1 + 0.375 Grazon P+D 2 pts picloram + 2, 4-D 0.135 + 0.5 Grazon P+D 3 pts picloram + 2, 4-D 0.2 + 0.75 Curtail 2 pts clopyralid + 2, 4-D 0.095 + 0.5 Curtail 3 pts clopyralid + 2,, 4-D 0.14 + 0.75 Curtail 4 pts clopyralid + 2, 4-D 0.19 + 1.0 Cimarron + Rangestar 0.2 oz + 1 pt metsulfuron + 2, 4-D + dicamba 0.008 + 0.36 + 0.125 Cimarron + Rangestar 0.2 oz + 2 pts metsulfuron + 2, 4-D + dicamba 0.008 + 0.72 + 0.25 Cimarron + Rangestar 0.3 oz + 2 pts metsulfuron + 2, 4-D + dicamba 0.01 + 0.72 + 0.25
Influence of Herbicide Treatments on Short- & Long- Term Ironweed Control in Tall Fescue Pastures Treatments b 2004 & 2005 Combined Data Ironweed Control a Rate 2MAT 2004 2 MAT 2005 1 Year After Treatment product/a ---% Visual Control --- --- # Stems/Plot --- 2, 4-D 1 qt 85 a 18 def 201 a 2, 4-D + Banvel 1 qt + 1 pt 84 a 31 bcd 121 ab Grazon P+D 1.5 pts 90 a 45 bc 114 ab Grazon P+D 2 pts 94 a 48 b 139 ab Grazon P+D 3 pts 98 a 83 a 74 b Curtail 2 pts 85 a 25 cde 138 ab Curtail 3 pts 84 a 33 bcd 119 ab Curtail 4 pts 87 a 44 bc 86 b Cimarron + Rangestar 0.2 oz + 1 pt 45 c 16 def 181 ab Cimarron + Rangestar 0.2 oz + 2 pts 67 b 19 def 172 ab Cimarron + Rangestar 0.3 oz + 2 pts 65 b 9 ef 135 ab Untreated --------- 0 d 0 f 221 a a Means followed by similar letters are not significantly different according to P=0.05. b All treatments were applied with a non-ionic surfactant at 0.25% v/v.
Untreated 3 pts Grazon P+D
Influence of Herbicide Treatments on Total Forage Yield of Tall Fescue Pastures (July Harvest 2004 & 2005) Treatments b Rate Total Forage Yield a product/a ---- lbs/acre ---- 2, 4-D 1 qt 1814 b 2, 4-D + Banvel 1 qt + 1 pt 1627 b Grazon P+D 1.5 pts 1714 b Grazon P+D 2 pts 1736 b Grazon P+D 3 pts 1608 b Curtail 2 pts 1750 b Curtail 3 pts 1773 b Curtail 4 pts 1629 b Cimarron + Rangestar 0.2 oz + 1 pt 1740 b Cimarron + Rangestar 0.2 oz + 2 pts 1806 b Cimarron + Rangestar 0.3 oz + 2 pts 1743 b Untreated --------- 2347 a a Means followed by similar letters are not significantly different according to P=0.05. b All treatments were applied with a non-ionic surfactant at 0.25% v/v.
Influence of Herbicide Treatments on Forage Quality of Ironweed-Infested Tall Fescue Pastures (July Harvest 2004 and 2005) Total Forage Analysis a Treatments b Rate ADF NDF Protein product/a --------------------------- % --------------------------- 2, 4-D 1 qt 33.9 ab 59.2 ab 8.0 abc 2, 4-D + Banvel 1 qt + 1 pt 34.3 a 60.2 a 7.9 bc Grazon P+D 1.5 pts 34.0 ab 60.6 a 7.8 bc Grazon P+D 2 pts 34.1 ab 60.6 a 7.8 bc Grazon P+D 3 pts 34.2 ab 60.6 a 8.1 abc Curtail 2 pts 33.7 ab 59.2 ab 8.2 abc Curtail 3 pts 33.9 ab 59.8 ab 7.9 bc Curtail 4 pts 34.4 a 60.4 a 7.9 bc Cimarron + Rangestar 0.2 oz + 1 pt 33.0 b 57.7 bc 8.6 a Cimarron + Rangestar 0.2 oz + 2 pts 33.7 ab 59.5 ab 8.2 abc Cimarron + Rangestar 0.3 oz + 2 pts 33.0 b 58.3 abc 8.4 ab Untreated --------- 33.0 b 56.0 c 7.7 c a Means followed by similar letters are not significantly different according to P=0.05. b All treatments were applied with a non-ionic surfactant at 0.25% v/v.
Influence of Herbicide Treatments on Total Forage Yield of Tall Fescue Pastures (November Harvest 2004 & 2005) Treatments b Rate Total Forage Yield a product/a ---- lbs/acre ---- 2, 4-D 1 qt 1437 a 2, 4-D + Banvel 1 qt + 1 pt 1560 a Grazon P+D 1.5 pts 1373 ab Grazon P+D 2 pts 1582 a Grazon P+D 3 pts 1535 a Curtail 2 pts 1538 a Curtail 3 pts 1466 a Curtail 4 pts 1501 a Cimarron + Rangestar 0.2 oz + 1 pt 1451 a Cimarron + Rangestar 0.2 oz + 2 pts 1623 a Cimarron + Rangestar 0.3 oz + 2 pts 1618 a Untreated --------- 1113 b a Means followed by similar letters are not significantly different according to P=0.05. b All treatments were applied with a non-ionic surfactant at 0.25% v/v.
Influence of Herbicide Treatments on Forage Quality of Ironweed-Infested Tall Fescue Pastures (November Harvest 2004 & 2005 Combined Data) Total Forage Analysis a Treatments b Rate ADF NDF Protein product/a --------------------------- % ------------------------- 2, 4-D 1 qt 25.2 ab 49.9 a 10.8 ab 2, 4-D + Banvel 1 qt + 1 pt 25.4 ab 50.5 a 10.6 ab Grazon P+D 1.5 pts 24.5 b 50.0 a 10.9 ab Grazon P+D 2 pts 24.8 ab 50.4 a 11.0 a Grazon P+D 3 pts 24.9 ab 50.3 a 10.9 ab Curtail 2 pts 24.9 ab 50.1 a 10.8 ab Curtail 3 pts 24.9 ab 49.9 a 10.6 ab Curtail 4 pts 25.1 ab 50.1 a 10.8 ab Cimarron + Rangestar 0.2 oz + 1 pt 25.2 ab 50.2 a 10.8 ab Cimarron + Rangestar 0.2 oz + 2 pts 25.6 a 50.8 a 10.8 ab Cimarron + Rangestar 0.3 oz + 2 pts 25.4 ab 50.4 a 10.9 ab Untreated --------- 25.3 ab 49.9 a 10.4 b a Means followed by similar letters are not significantly different according to P=0.05. b All treatments were applied with a non-ionic surfactant at 0.25% v/v.
Conclusions Good (>80%) tall ironweed control was observed during the season of treatment with all treatments except Cimarron + Rangestar 1 YAT, all treatments provided similar reductions in tall ironweed stems, but 2, 4-D + Banvel and high rates of Grazon P+D and Curtail reduced ironweed populations from to 62 to 73%
What can we learn from this example? In the case of ironweed, herbicide treatments DID NOT improve forage quality when compared to the untreated control but how many times will we find this kind of situation? As for the effects of weeds on forage quality, the question you should ask is, DO THE CATTLE EAT IT? Ironweed is still a top-5 weed in Missouri! Initially, herbicide treatments will REDUCE total forage yield, especially in weedy areas. Eventually, yields will recover and return to normal or higher levels. In this example, in one year s time herbicide treatments increased total forage yield 27% (404 lbs). At $60/ton, this is equal to $12 MORE PER ACRE. Is this enough to make a herbicide treatment worthwhile?
Approximate Pasture Herbicide Costs Treatment Price / Unit "Standard" Rate / Acre Price / Acre 2,4-D $16.00 / gal 1 qt $ 4.00 Banvel $78.00 / gal 1 pt $ 9.75 Cimarron $27.54 / oz 0.2 oz $ 5.51 Cimarron Max $138.57 / co-pack "Rate 1" $ 6.93 Crossbow $48.25 / gal 2 qts $24.13 Forefront $62.00 / gal 2 pts $15.50 Grazon P+D $36.15 / gal 2 pts $ 9.04 Milestone $92.99 / qt 4 fl ozs $11.62 PastureGard $45.39 / gal 2 pts $11.35 Redeem $80.00 / gal 2 pts $20.00 Remedy $89.25 / gal 2 pts $22.31 Surmount $50.35 / gal 2 pts $12.59 Tordon 22K $90.66 / gal 1 pt $11.33