Controlling noxious weeds in your yard

Central Florida is home to some of the most diverse plant life in the state.

Cool, dry winters and hot, wet summers create a transitional zone where a variety of plants thrive, or can at least get by with a little help from their owners.

With the good news, comes the bad news — there are dozens of weeds that cause grief for property owners and managers.

Brazilian Peppertree. Image used in the 2014 Research Discoveries report. (Courtesy of UF/IFAS Communications)

Noxious weeds, which can out-compete native species, can be quite damaging.

In Central Florida, three common noxious weeds of great concern are: Brazilian peppertree, air potato vine, and cogongrass.

Brazilian peppertree was introduced perhaps more than 100 years ago as an ornamental plant.

Common along roads and canals, Brazilian peppertree has destroyed much of the native, protective mangroves and pine flatlands.

While attractive, its ability to overtake native vegetation and its potentially hazardous sap — which can cause severe rashes and lung irritation — make it undesirable.

Herbicide applications are effective for controlling Brazilian peppertree, but only when timed right and applied correctly.

The “cut stump method” of herbicide application is an excellent method for control.

Simply follow these steps:

  • Cut the tree stump as low to the ground as possible.
  • Within 5 minutes of making the cut, apply a herbicide labeled for use on Brazilian peppertree (with the active ingredients: triclopyr at the label rate, or glyphosate at 41% active ingredient or higher formulation, as ready-to-use formulas won’t be effective) just inside of the bark layer on the living tissue.
  • Cut the trees only when they are not fruiting; if seeds are visible, use great care to not spread them to new locations.
  • Avoid the sap, and use proper protective gear with cutting or removing these plants.
  • Do not burn Brazilian peppertree due to the potential for hazardous fumes from the sap.

Brazilian peppertree also can be controlled with a basal bark herbicide application. Consult with your local Extension Office for details on this method.

University of Florida Institute of Food and Agricultural Sciences scientists were granted approval for the release of a biological control for use on Brazilian peppertree in 2019. An insect species of thrips feed on the new shoots of Brazilian peppertree and have been found to be host-specific, meaning they only damage Brazilian peppertree.

Controlling other noxious weeds
Air potato vine is an extremely aggressive vine that can grow several inches in a day making it capable of towering up into the tops of trees while out-competing native vegetation along the way.

Biological controls, combined with other integrated pest management approaches, such as herbicide use, mechanical (removal) and cultural methods (proper timing, application methods, seasonality, etc.) have been highly effective at controlling air potato vine.

The release of the Air Potato Beetle, in 2012, by the Florida Department of Agriculture and Consumer Sciences, in conjunction with UF/IFAS, has helped limit the spread of air potato vine.

Cogongrass is common throughout the Southeastern United States, taking over roadsides, fields, pine-forested areas and pasturelands. It is difficult to control and can be a fire hazard, too.

Early detection of cogongrass infestations is the key to control. Small areas of infestation are easier to manage compared to larger ones. There are two herbicides with effectiveness against cogongrass: glyphosate and imazapyr. Glyphosate is most advisable, since it does not persist in the soil. Just keep in mind that both herbicides can kill non-target plants. Multiple herbicide applications over several years is often necessary for control with frequent monitoring required to quickly treat any regrowth following herbicide applications.

Again, your local Extension Office can provide more guidance on how to attack these types of noxious weeds and others wreaking havoc in your landscape.

For a list of noxious weeds, visit the UF/IFAS Invasive Plant Assessment by going to https://assessment.ifas.ufl.edu/.

By Whitney C. Elmore

Dr. Whitney C. Elmore is the UF/IFAS Pasco County Extension director and an Urban Horticulture Agent III.

Published December 04, 2019

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