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- Roots, Shoots, Fruits & Flowers: Organic Burweed Control, Monarch Caterpillar & Ragweed ID & Control
Lawn burweed, a cool season weed. Photo: Dan Gill, LSU AgCenter, retired.
Erin read an article about lawn burweed from the AgCenter and then sent this email, “I do not want to use herbicide. How [do I] stop burweed before it starts?”
Here are some practices from a publication, Louisiana Home Lawn Series: Lawn burweed, that enable a healthier lawn and fewer weeds:
“The best way to prevent or reduce weed encroachment is to maintain a healthy lawn through proper fertilization and soil pH and regular mowing. Properly maintaining a lawn through these cultural practices promotes dense and vigorous turfgrass, allowing it to better compete with weeds. Below are the recommended mowing heights and nitrogen fertility rates recommended per turfgrass species.
| Turfgrass | Mowing height | Nitrogen Rate (per 1,000 ft² per year) |
| Bermudagrass | 1-2 inches | 2-3 pounds |
| Centipedegrass | 1-2.5 inches | 0.5-2 pounds |
| St. Augustine Grass | 2.5-3 inches | 1-3 pounds |
| Zoysia | 1-2.5 inches | 0.5-2 pounds |
Recommended Mowing Heights & Fertility Rates.
In addition to these lawn care practices; manual removal of weeds may also be necessary.” Also, you can try these organic herbicides:
| Herbicide (Active Ingredient) |
Common or Trade Name | Pre- or Post-Emergent | Selective or nonselective |
| Corn gluten | Preen Organic Vegetable Garden |
Pre-emergent | Nonselective |
| Pelargonic acid | Scythe | Post-emergent | Nonselective |
| Clove oil, citric acid, Lecithin | Perfectly Natural Weed, Grass & Moss Killer |
Post-emergent | Nonselective |
| Acetic acid | Vinegar | Post-emergent | Nonselective |
These organic herbicides tend to perform well on annual weeds, and burweed is annual plant.
A caterpillar of the Monarch butterfly. Photo: Molly Poe, DeRidder, LA
Molly sent a clear picture and wanted to know, “I am hoping this is a butterfly caterpillar?”
Yes, Molly’s caterpillar will become a monarch butterfly, they feed on milkweeds. The website of the Cajun Prairie Garden shares this list of native milkweeds:
Cajun Prairie species:
*Asclepias amplexicaulis Claspingleaf (Blunt-leaf) milkweed
*Asclepias humistrata Coastal milkweed
Asclepias lanceolata Fewflowered (Red) milkweed
Asclepias longifolia Longleaf milkweed
Asclepias obovata Pineland milkweed
Asclepias perennis Aquatic (Shore) milkweed
Asclepias tuberosa Butterflyweed
*Asclepias variegata White (Redring) milkweed
Asclepias verticillata Whorled milkweed
Asclepias viridiflora Green Comet milkweed
Asclepias viridis Green (Antelopehorn) milkweed
*Not found in the open prairies and marshes, but in adjacent forests and along the coast in sandy areas—these areas are within the Cajun Prairie ecosystem.
Ragweed seedling Photo: Dr. Daniel Stephenson, LSU AgCenter
Ragweed seedling Photo: Dr. Daniel Stephenson, LSU AgCenter
Lana Craig, 4-H Agent in Grant Parish, sent a message with some pictures, “Two gentlemen brought this plant to my office today and pictures. They asked if you could identify it and tell them how to kill it. It has taken over their gardens.”
Dr. Daniel Stephenson, an AgCenter crop agronomist specializing in crop weeds, helped with the identification, “That is ragweed parthenium.” He recommended this aggressive treatment for this weed, “Permanent eradication with a single herbicide application will be close to impossible. It can be accomplished, but eradication will take time.
The best non-selective herbicide treatment is glyphosate (Roundup and many other formulations) when the parthenium is exceedingly small (See photo below for example).
If the plant is the size of the plant in the attached photo, then it will need to be physically removed with tillage or hand removal because glyphosate does not provide satisfactory control. Ragweed parthenium can germinate year-round, but predominately emerges March through October. So, eradication will be a process that can include chemical and physical weed management means.”
If you want to contact Roots, Shoots, Fruits, and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337.284.5188 or khawkins@agcenter.lsu.edu.
“Before you buy or use an insecticide product, first read the label, and strictly follow label recommendations. Mention of trade names or commercial products in this article is for informational purposes only and does not constitute endorsement by Louisiana State University AgCenter.”
“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”