Dogfennel (Eupatorium capillifolium): Biology and Control1
B. A. Sellers, Pratap Devkota, and J. A. Ferrell
Dogfennel ( Eupatorium capillifolium ) is an aggressive native perennial found throughout much of the Southeast. Dogfennel is peculiarly troublesome in unimproved or overgrazed pastures where it adds to the decline of eatage output and quality. Although dogfennel is broadly considered to be entirely unsightly, inquiry has shown that significant bahiagrass give loss will be observed when dogfennel infestations are not removed prior to July 1. Cattle do not normally feed on dogfennel, but they may eat it when more suitable forages are lacking. however, the leaves contain low levels of the toxin tremitol, which causes dehydration when ingested by cattle. Dogfennel is presently the number one most normally occurring pasture weed in Florida .
Dogfennel growth frequently occurs from overwintering rosettes, but seeds will besides sprout and grow when land temperatures reach 65°F. The emergence will broadly consist of a individual, non-branching shoot that can exceed 8 feet in height. The leaves are very slender ( Figure 1 ) and emit a strong olfactory property when crushed. Near Gainesville, Florida, the life sentence bicycle will resemble the information found in mesa 1, and these growth patterns will occur earlier in South Florida .
figure 1 .
credit : Jason Ferrell, UF/IFAS
Table 1. Life cycle of dogfennel near Gainesville, FL .
Seeds are surrounded with hairs ( exchangeable to dandelion ), allowing effective dispersion by wind. therefore, bare areas in pastures are ideal environments for windblown seed to become established .
In addition to increase from sow, dogfennel can spread from underground rootstocks. These rootstocks arise from the main taproot and grow laterally in all directions. This summons will result in the production of distinct plant colonies in entirely three years .
calculate 2 .
recognition : Jason Ferrell, UF/IFAS
Herbicide Timing and Selection
Although we have a reasonably thorough understand of dogfennel biology, there is no specific month when an herbicide application for dogfennel control is recommended. preferably, it is much more crucial to select an herbicide program based on dogfennel height ( table 2 ). little plants are much easier to control than larger ones. In fact, dogfennel less than 20 inches in stature is readily controlled with 2 qt/A 2,4-D amine or 1.5 qt/A WeedMaster ( dicamba + 2,4-D amine, others ). manipulate with these herbicides tends to decline as dogfennel plants grow above 20 inches. however, it is not uncommon to reach levels of 80 % –85 % control with these herbicides when plants are between 20 and 36 inches tall. Above 36 inches, the tied of control is dramatically reduced and a more rigorous herbicide program is recommended .
There are respective options for controlling bombastic dogfennel ( table 2 ). When choosing an herbicide program, we need to consider the weed spectrum within a given eatage american samoa well as the eatage grass present. If dogfennel is the basal prey pot in the pasture, Pasturegard HL at 1.5 pt/A is an extremely effective option regardless of the establish ‘s size at the clock of application. however, if early weeds such as tropical sodium carbonate apple are give, we recommend applying GrazonNext HL at 1.5 pt/A in combination with 1 ) Pasturegard HL at 0.5 pt/A, 2 ) 2,4-D amine at 3 pt/A, or 3 ) 2,4-D + dicamba at 2 pt/A. All of these herbicide combinations can be safely applied with minimal injury to forages in Florida. The entirely exception is that products containing 2,4-D should not be applied to limpograss ( Hemarthria ) between May 1 and November 1, as austere injury may occur. For more information concerning weed management in limpograss, please refer to the EDIS publication Weed Management in Limpograss ( hypertext transfer protocol : //blog.naivepets.com/ag344 ) .
In accession to dogfennel height, there are environmental factors to consider. The driest time of year, specially in South Florida, is April and May when most dogfennel is relatively small. tied though small dogfennel is typically the easiest to control, herbicide effectiveness can be badly impacted by drought conditions as plants tend to “ harden-off ” to limit water system loss. In most cases, adenine long as the plant is not wilting during the day, the herbicides listed in postpone 2 will provide effective control. however, it is authoritative that application rates are not reduced. We have seen 2,4-D amine and 2,4-D amine + dicamba fail to efficaciously control dogfennel under dry territory conditions on several occasions .
Dogfennel Infestation and Forage Production
There is no doubt that weed infestations have a damaging impact on bahiagrass output. Until recently, however, the extent of the impact was not known. In an experiment conducted in 2007 and 2008, season-long production of bahiagrass was measured in response to the time of dogfennel removal at increasing dogfennel densities .
The data bespeak that a eatage with > 50 % infestation will yield 42 % –74 % less bahiagrass than a dogfennel-free pasture, if dogfennel removal is performed in May. Waiting until August to remove dogfennel from pastures with > 50 % infestation resulted in a more than 75 % loss in bahiagrass return. As such, we recommend that dogfennel be controlled a early as potential if more than half the pasture is infested .
experimental pastures with < 25 % dogfennel cover had relatively consistent bahiagrass yields as the growing season progressed. even though the bahiagrass concede was lower than the plots without dogfennel, it appears that bahiagrass is slightly tolerant of light up dogfennel infestations. The lapp does not hold true for higher levels of dogfennel infestations. Bahiagrass output declined as the growing temper progressed in both 50 % dogfennel cover plots angstrom well as > 75 % dogfennel cover plots .
From this research we concluded that when pastures are infested with < 25 % dogfennel cover, herbicide applications may be delayed for about a whole grow season, specially if dogfennel plants have become so large that more expensive herbicide mixes are needed for optimum restraint. conversely, at dogfennel cover > 50 %, dogfennel should be controlled equally early on as potential to prevent substantial concede loss and potential stand reductions .
Dogfennel is an important plague that is more destructive to bahiagrass pastures than may be realized. We believe it is significant to focus on this weed and remove it as infestations increase beyond 25 % groundcover. unfortunately, providing a “ one size fits all ” recommendation for dogfennel see is unmanageable, if not impossible. Each eatage is going to require some think with gaze to herbicide excerpt and application clock based on both the environment and dogfennel density. We recommend you review the data in this article, along with the following EDIS articles :
- Tank-Mix Options for Control of Tropical Soda Apple and Dogfennel ( hypertext transfer protocol : //blog.naivepets.com/ag306 )
- Weed Management in Pastures and Rangeland ( hypertext transfer protocol : //blog.naivepets.com/wg006 ).
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If you need aid with your particular position, please contact your local UF/IFAS Extension agentive role .
Table 2. herbicide options for dogfennel restraint in pastures. herbicide costs are estimated and may vary upon the amount purchased ; cost of application is not included in the herbicide price .
The use of deal names in this publication is entirely for the determination of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this issue do not signify our approval to the exception of other products of suitable constitution. All chemicals should be used in accordance with directions on the manufacturer ‘s label .