by Matthew Orwat | May 12, 2016
Burweed, Soliva Sessilis. – Image Credit: Joseph M. DiTomaso, University of California – Davis, Bugwood.org. Creative Commons License
This spring, lawn burweed has been an especially noticeable problem in lawns. Extension offices throughout Northwest Florida have been fielding many questions and finding solutions to lawn burweed infestations!
On the top of my list of lawn related annoyances is stepping into a patch of burweed, Soliva sessilis, which is in the sunflower family and is also known as spurweed. The leaves are opposite along the stem and sometimes resemble parsley. The main ways in which burweed can irk the casual gardener are sticking to socks, sneaking in with the dog, or littering flower beds with its nuisance. It can also hide in the house and reappear when shoes are removed. This causes pain in both the foot and the ear.
Aside from herbicides, maintaining a healthy vigorous lawn will prevent weeds from taking over. If your lawn is reasonably healthy and only a few instances of this weed exist, try to mechanically remove them and encourage the lawn to outgrow them.
If cultural methods aren’t sufficient, science has given us several options to control this irksome pest. Herbicides containing the active ingredients dicamba, 2,4-D or atrazine are good at controlling burweed as a post emergence control when applied from December through March. Be careful to use reduced rates on centipede and St. Augustine lawns, and never use more than the labeled rate since injury can occur when using these products on these species. Later applications have less effect on burweed because as it matures it is harder to control. Additionally the burs, once present on the lawn, are hard to remove. As the daytime temperatures rise to 90ºF, some of these herbicides may cause lawn damage. Try to keep the spray residue outside of the root zone of desirable plants to avoid injury and always follow label directions.
Be aware that burweed reproduces by seed, so mowing it down will only increase the problem by burying the seed for fall germination. Although we are now in the month of May, control of actively growing burweed might still be warranted if it is still flowering and setting seed. As temperatures warm up burweed will die, as it is a winter annual. In cases where it is already dying, control is not warranted since the natural cycle of winter annuals is concluding.
If an infestation of burweed has occurred this year, take note. The best time to apply pre-emergent herbicides to control burweed is in October. A widely used preemergence product for burweed control is isoxaben, which is sold under the brand name of Gallery as well as others. It prevents the weed from emerging from the ground when it germinates and can be used on St. Augustine, centipede, bahia and zoysia lawns, as well as in ornamental shrub beds. In northwest Florida, this herbicide needs to be applied in October for best results. A second application later in the season might be warranted. For more information about control, please consult this excellent article on lawn burweed management.
The active ingredients mentioned above are present in a variety of ‘trade name’ products* available from your local garden center, farm supply or co-op. Be sure to read label instructions carefully and contact your local extension office for any assistance. I hope all the northwest Florida lawn managers prevent burweed during the upcoming fall so that lawns will be burweed free next spring.
Happy Gardening!
by Les Harrison | Feb 10, 2016
Weeds grow everywhere, especially in manicured lawns and landscapes despite the best efforts of owners who have spared no expense to remove the offending flora.
The reality, at least about the herbicides, is different from perceived appearances. Herbicides can be a wonderful tool for the homeowner, if applied properly.
The first point to remember about herbicides is to always, Always, ALWAYS apply them as instructed by the label directions. The oft quoted mantra of “the label is the law” is accurate.
Herbicides and their labeling are periodically reviewed and assessed to confirm effectiveness against target weeds without damaging the environment. Not following the label directions can have many negative implications for both the environment and the applicator.
Herbicides are either selective or non-selective when killing plants. Non-selective herbicides kill or damage every plant, but selective herbicides target a narrower range of plants.
Annual Bluegrass – Image Credit Larry Williams
Never apply herbicides when there is a breeze or wind. Herbicide drift can injure or destroy plants that are not the intended target.
High temperatures can contribute to the drift problem by volatizing some of the herbicide spray. Even the lightest air movement will cause drift off the target weeds when this condition exists. Herbicide drift can also be deposited in ponds and streams, harming the aquatic creatures that live there. Some herbicides are toxic to fish, insects and other animals that can be killed by tiny amounts of the active chemical. Additionally, the off target herbicides can kill aquatic plants. When the dead plants decay, they deplete the water of oxygen, again threatening or ending the life of the water’s residents.
Rain or dew resulting from high humidity can negate a herbicide’s application. If a leaf is wet, most or all the herbicide will run off on to the soil where it can leach into the water table.
Regular herbicides work only when the plant is actively growing. Pre-emergent suppresses the growth of the weed seedling above the soil level.
Many weeds have already produced seeds for next spring. Herbicides applied now will not affect the germination of that seed months from now.
The most effective strategy is to mow weeds before they set seed or to collect and destroy those which have already produced seed. Even with 100 percent success at eliminating this year’s weed seed crop, there will be weeds next year.
Some weed seed remain in the soil, sometimes for decades, only to germinate when conditions are perfect for their sprouting. Sickle pod and crotalaria are local examples of long term seed vigor.
Other seed can blow in or be dropped by wild or domestic animals passing through the property. A pre-emergent herbicide which stops germination can help control these latent invaders.
For more information:
Weed Management Guide for Florida Lawns
Chemical Weed Management
by Mary Salinas | Oct 14, 2015
Cogongrass dominating the landscape. Photo credit: Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org.
A U.S. Forest Service grant is again available to assist non-industrial private landowners with the cost of controlling cogongrass. Applications will be accepted starting October 15, 2015. The program reimburses landowners for 50% of the cost for two consecutive years with a maximum reimbursement of $10,000 for each year.
Cogongrass is one of the worst invasive plant species in Northwest Florida as it marches through natural areas and literally chokes out our desirable native vegetation as it goes. The underground rhizomes continually expand patches of the grass in every direction and its prolific seed production carries infestations to new areas.
Note the off center midrib along the leaf blade. Photo credit: Chris Evans, Illinois Wildlife Action Plan, Bugwood.org.
There are several ways to accurately identify cogongrass. The leaf blades are flat with serrated edges and tend to be yellowish-green in color. The midrib which runs lengthwise up each leaf blade is white and is distinctly off-center. The seed head which arises in the spring is a fluffy white plume. Since it spreads through rhizomes, cogongrass is often seen in expanding circular patches.
The fluffy white plume of the seedhead. Photo credit: Chris Evans, Illinois Wildlife Action Plan, Bugwood.org.
If you need assistance with the identification of cogongrass, please consult your local Extension office.
For more information:
Cogongrass Treatment Cost-Share Program
Cogongrass (Imperata cylindrica) Biology, Ecology, and Management in Florida Grazing Lands
by Mary Salinas | Feb 2, 2015
So often, homeowners wait until weeds have overtaken their lawns in mid-summer before looking for a course of action to control them. Unfortunately, when weeds get to maturity and start producing flowers and going to seed, they are usually quite difficult to control.
[important]The best strategy is to prevent the weeds from getting established in the first place![/important]
Florida pusley, an annual weed that can be controlled with preemergence herbicides. Photo credit: Mary Derrick UF/IFAS Extension.
When properly applied, a preemergence herbicide forms a chemical barrier on the surface of the soil that kills newly germinated seeds when they grow and contact that barrier. Be sure to follow label directions carefully as it is crucial to apply the correct amount and water it in correctly. The soil surface should not be disturbed after application to ensure that the chemical barrier remains intact.
Keep in mind that preemergence herbicides only prevent annual weeds! They do not control weeds that have already emerged.
In North Florida, the time to apply a preemergence herbicide to your turfgrass is coming soon. As a general rule, March 1 is an ideal time. Another indicator that the time is right is when the daytime temperatures reach 65°F-70°F for 4 to 5 consecutive days as that sustained warmth will prompt weed seeds to germinate. Oftentimes, this is also when azaleas or dogwoods start blooming and that can clue you into when to apply the herbicide. For best results, follow up with a second application in 6 to 9 weeks to control those seeds germinating later in the season.
Always follow the label instructions precisely when applying any herbicide! Ensure that you apply the product at the correct rate, that it is suitable for your specific turfgrass and situation, and that it is watered in correctly. For any pesticide, the label is the law!
If your lawn has problems with winter weeds, make a note on your calendar to apply a preemergence herbicide about October 1 in North Florida or when nighttime temperatures drop to 55°F-60°F for several consecutive days.
For more information on weed control in lawns:
Weed Management Guide for Florida Lawns
For general information on lawn care in Florida:
UF/IFAS Gardening Solutions: Lawns
