Roots, Shoots, Fruits & Flowers: Virginia Buttonweed, Asian Dayflower, Crawfish Chimneys, and Blossom End Rot


Virginia buttonweed, a common weed. Photo: Darren Smith.

Virginia Buttonweed

Darren sent in an image of a common lawn weed, and asked, “Hey, could you guys give us a weed ID and a recommendation of what to use to kill it?”

This weed looks like Virginia buttonweed (VBW). Will Afton, an AgCenter horticulture agent, writes about treatment for VBW in lawns, “Four way herbicides (2,4-D + dicamba + mecoprop + carfentrazone) can be used during the months of April, May and June before the average high temperature exceeds 85°F. Some of the common trade names include Speed Zone Southern ® and Weed Free Zone®.

If applications are needed later in the season, use the active ingredient metsulfuron. It can be found in MSM Turf®. One of the most effective herbicides to control Virginia buttonweed is Celsius ® (iodosulfuron + thiencarbazone + dicamba). Both herbicides can be applied when temperatures exceed 85°F. Remember to always read and follow label instructions before applying any pesticides.”

615_fig_2_asian_dayflowerjpgAsian or spreading dayflower. Photo: Louisiana Agricultural Consultants Association.

Asian Dayflower

A gardener complained about the Asian dayflower in her flower beds, “I tried Roundup® and a vine killer but neither worked. I also painted on grass killer [but it] hasn't worked either.”

Asian or spreading dayflower is a weed in both agriculture and in horticulture. Dr. Ron Strahan recommends, “I would apply Trimec Southern® or Fertilome Weed Free Zone®. Repeat, as necessary. Expect temporary lawn injury.” In a flower bed, these products need to be applied with paint brushes to avoid damage to desirable ornamental plants.


A crawfish chimney, a common nuisance in landscapes. Photo: LSU AgCenter.

Crawfish Chimneys

Tim had heard of using ducks in a vegetable garden to control insects. He wanted to consult with the AgCenter about using ducks to eliminate crawfish from his yard.

Dr. Greg Lutz commented on the duck method of treating crawfish, “It might work, but it would probably take 2 or 3 years to get them all. And even then, the crawfish are out on rainy nights, so I don’t know if the ducks would be awake to eat them.”

Dan Gill, retired AgCenter horticulturist, offers a more practical idea for managing crawfish in lawns, “Putting some lye in the crawfish burrows (about a tablespoon full) usually does the job of controlling them in lawn areas. And, as it migrates through the surrounding soil, it turns into harmless by-products. When using lye, remember that it is caustic. Be sure to wear hand and eye protection and protective clothing.”


Blossom end rot in tomatoes, a nutrient deficiency. Photo: Dr. Heather Kirk-Ballard, LSU AgCenter.

Blossom End Rot

Lee called the AgCenter asking about a rot on his container-grown tomatoes.

Lee has a condition called “blossom end rot” or BER. Dr. Heather Kirk-Ballard wrote about this topic in a recent article, “The first disorder that often affects tomatoes is blossom end rot. The telltale sign is a sunken black spot on the bottom of the fruit where the blossom once was. This indicated you need to adjust your watering. The spots become enlarged by decay-causing organisms that infect the compromised fruit. Try using a soaker hose or drip irrigation to help with consistent water delivery to allow the plant to efficiently process the calcium that is also associated with blossom end rot.

Calcium deficiency in the developing fruit can be an issue. In combination with fluctuations in moisture caused by over- and under-watering, high humidity and rainy or cloudy weather. The problem can be exacerbated by excess ammonia forms of nitrogen (ammonium sulfate and ammonium nitrate) in complete fertilizers such as 10-10-10, potassium or magnesium because they compete with calcium for uptake in the plant.”

Dr. Kirk-Ballard recommends this solution for BER, “You can help treat blossom end rot by using limestone applied three to six months before planting or adding gypsum (calcium sulfate) applied to the soil at 1 to 2 pounds per 100 square feet. The soil pH should be 6.5. A calcium nitrate sidedress fertilizer is usually the best choice and is applied monthly at 2 pounds per 100 feet of row. You can also apply gypsum at 1 to 2 pounds per 100 square feet as a sidedress treatment.”

If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or Also, you can be on the “green thumbs” email list by emailing your request to the address above.

“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.

6/16/2020 7:47:30 PM
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