More lichens, Pond Weeds & Bloomless Hibiscus

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Figure 1: Lichens
Photo: Dr. Raj Singh, LSU AgCenter

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Figure 2: Pond edge infested with grasses-Photo: John Trahan

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Figure 3: Luna Hibiscus-Photo: LSU AgCenter

After last week’s RSFF, Ms. Chaery asked about the paragraph regarding lichens, “Concerning the pecan trees, would the next step possibly be to do a soil sample? What would help determine the problem?” AHA responded, “Thank you for your question. All I had to diagnose the problems with the trees were the pictures of lichens and no other information about the trees. Yes, a soil test would be a good start. I would welcome the chance to make a site visit to examine the trees and make a more definite diagnosis of the tree.” A site visit would enable an examination of the growing conditions affecting the trees. A few pictures of lichens helps very little.

Ms. Linda also had a question about lichens, “I have seen the lichens you described before several times. Is there a chemical to kill it?” The answer would be “yes”. A fungicide will kill lichens, but the lichens would just come back, and the applicator of the fungicide would have wasted the cost of the product. The lichens are harmless and more of a symptom of a problem rather than a cause.

John of Ragley, LA sent his email, “We purchased our home almost seven years ago, and it has a small pond on the property. At first we didn’t have any problems with weeds in the pond. Over the last three years or so the weeds have gone from manageable with a weed-eater to uncontrollable because of the quantity of the weeds, and they are now growing so far out in the water that I can’t reach them with a weed-eater any longer.

We have a few small fish in the pond, and my grandchildren enjoy catching and releasing the fish back into the pond. [Fishing] is hard to do now with the weed problem.

I started looking for a solution to the problem and realized that there are several herbicides for ponds, but each one is for certain type of weed, and I really don’t know what type is in my pond.”

Sean Kinney, Fisheries Biologist with the LA Department of Wildlife & Fisheries (LDWF), identified the weed as maiden cane. He also made this treatment recommendation, “I would suggest 1 of two treatments of herbicide. Each of these may take multiple treatments as it will be hard to ensure 100% coverage with the plant coverage.

Treatment 1: Glyphosate (approved for aquatic application: Roundup Custom) at .75 gallons per acre with .25 gallons of surfactant (methylated seed oil or nonionic surfactant) (this is a 100 gallon mixture).

Treatment 2: Imazapyr at .5 gallons per acre with .25 gallons of surfactant (methylated seed oil or nonionic surfactant) (this is a 100 gallon mixture).

The Imazapyr is the stronger of the 2 treatments and care should be taken during spraying to stay away from trees and only treat on low wind days. Each will take a month or so to see how well the treatment worked (browning at 2 to 3 weeks).

With a pond this small it is important that he understand that he still needs to harvest fish. It looks shallow and if he is so inclined he can call me to discuss. “

Ms. Terri shared a thoughtful email on behalf of a relative, “My cousin in Lake Charles is wondering why her hibiscus are not blooming. They are growing just fine.”

AHA shared this answer to Ms. Terri’s question, “There may be two different reasons for the lack of blooms:

  1. She may have trimmed the plant too late and pruned out the flower buds. In general, the best time to trim back an ornamental plant is shortly after bloom.
  2. The other reason may be the lack of phosphorus and potassium. Start with a soil test and then fertilize based on the recommendations. Soils test kits are available at local AgCenter offices.

I hope these notes help your cousin.”

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.”

7/8/2019 7:56:15 PM
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