I have had several questions concerning limpograss (Hemarthria) tolerance to various herbicides.
Dicamba (Banvel) has been the standard recommendation for weed control in limpograss, because Weedmaster
contains 2,4-D, which has been reported to cause significant limpograss injury. Over the past couple of
years, we have had several herbicides labeled in the pasture market including: Cimarron, Telar,
Pasturegard, Overdrive, and Milestone. Little information regarding the tolerance of limpograss
to these herbicides has been recorded.
In a study initiated on 12 April, 2005, 2,4-D amine at 2, 4, and 8 pints/acre, Remedy at 1, 2, and
4 pints/acre, and Milestone at 3, 5, and 7 fluid ounces/acre resulted in no visual injury (chlorosis
and necrosis) three months after application to either non-mowed or mowed (10 inch regrowth at
application) limpograss. When not mowed prior to herbicide application, these herbicide treatments
did not impact limpograss production 6 months after treatment. However, if mowed prior to herbicide
treatment, a 17 to 23% yield reduction was observed from 4 and 8 pints of 2,4-D amine as well as 2
and 4 pints of Remedy. Milestone caused a 15%-30% yield reduction when limpograss was mowed prior
to application.
The lack of limpograss injury from applying 2 pints of 2,4-D was surprising. Therefore, a second
study was initiated on 16 September, 2005. Cimarron at 0.1, 0.2, and 0.4 oz/acre, Telar at 0.5 and
1.0 oz/acre, Pasturegard at 2, 3, and 4 pints/acre, Weedmaster at 1, 2, and 4 pints/acre, Banvel at
0.3, 0.5, and 1 pint/acre, 2,4-D amine at 0.8, 1.5, and 3.0 pints/acre, and Overdrive at 4 and 8
oz/acre were applied to 10 inch limpograss. Applications of Cimarron, Telar, Pasturegard at 2 and
3 pints, Banvel, 2,4-D at 0.75 pints, and WeedMaster at 1 and 2 pints caused less than 15% injury
(chlorosis and necrosis) 1 month after treatment (See figures). By 2 months after treatment, no
chlorosis or necrosis was present from any herbicide application. Although chlorosis was not present,
limpograss height was reduced by at least 15% from applications of Pasturegard at 4 pints, 2,4-D at 3
pints, WeedMaster at 4 pints, and both rates of Overdrive. Biomass was not recorded in this study.
At this point in time, Overdrive should not be applied to limpograss as injury was too severe. However,
Cimarron and Telar are additional options that can be considered. Pasturegard (<3 pints/acre) and Remedy
(<2 pints/acre) may also be applied to limpograss if some initial injury can be tolerated. At this point
in time, Milestone can be applied up to 7 fluid ounces/acre when limpograss growth is mature, but use
caution when applying this herbicide to newly formed growth. Additionally, limpograss appears to be more
tolerant than previously thought to 2,4-D amine as well as Weedmaster, but the effects of 2,4-D appear
to vary under different environmental conditions. Therefore, 2,4-D-containing products should not be
applied until the effects of 2,4-D on limpograss are fully understood. Also, keep in mind that new
limpograss growth may be more susceptible to herbicide injury than more mature stands.
Herbicides often cause injury to desirable species. How much injury can be tolerated is usually up to
the grower. However, removing weeds in a pasture will often outweigh the effects of an herbicide on
forage production, especially when injury is less than 15%. We will continue investigating the effect
of herbicide applications at different times of the year to gain a better understanding how herbicides
affect limpograss production.
Figures
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Figure 1. Untreated limpograss |
Figure 2. Response of limpograss to 2 pints/acre of Pasturegard four weeks after treatment. |
Figure 3. Response of limpograss to 0.5 pints/acre of Banvel four weeks after treatment. This rate of Banvel
is the same amount that would be applied in 2 pints of Weedmaster. |
Figure 4. Response of limpograss to 1.5 pints/acre of 2,4-D amine four weeks after treatment. This rate
of 2,4-D is equal to the same amount of 2,4-D in 2 pints of Weedmaster. |
Figure 5. Response of limpograss to 2 pints/acre of Weedmaster four weeks after treatment. |
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