Working in the Landscape: Soil Testing, Fig Rust, Southern Watergrass, and Insect Barriers


Soil test kits available to gardeners. Photo: Olivia McClure, LSU AgCenter

Soil Testing

Professional horticulturists use the AgCenter’s soil testing lab to help improve the performance of the landscape plants of their clients. Local extension agents serving every parish can assist landscape pros understand the fertilizer recommendations in each soil report.

Professional landscape people can obtain soil test kits at the local AgCenter office in each parish, and some garden centers will also have these kits. Horticulturists and nurserymen can sample the soil from flower beds and containers, vegetable gardens, from under fruit and shade trees, and from client’s lawns. There is also a testing for “soilless” mediums for the nursery professional. The kits are in USPS Priority Mailer boxes and include an order form, sampling directions and three zip-loc sacks. The soil samples, payment and the order form are placed in the mailer box and then placed in the nearest mailbox. The cost is $10 per sample and an additional $6 for the mailer. Normally, the results and fertilizer recommendation come back to the gardener in about a business week. The local AgCenter office in each parish will receive the same results, and the local extension agent can help with questions about the soil analysis.


Fig rust on leaves. Photo: Susan Ham, Father's Hope Nursery.

Fig Rust

Susan, a professional horticulturist, asked about her fig leaves, “Can someone diagnose the problem on this fig tree and a treatment please?”

The diagnosis for this disease is fig rust. Dan Gill, retired AgCenter horticulturist wrote, “This is a common fungal disease called fig rust. It generally shows up in late summer and fall and may cause premature defoliation. However, fig trees tolerate the damage well and recover just fine. [There is] no need to treat.”


Southern watergrass, a weed. Photo: Darren Smith, Highland Growers.

Southern Watergrass

Darren, a horticultural vendor, contacted the AgCenter about a grassy weed, “This [weed] came up in a yard where brown patch had killed the San Augustine [grass. How do you control it?]

Dr. Ron Strahan, an AgCenter weed specialist, identified the weed and made a recommendation, “[Is the weed from a] wet area? [There is] no selective control [so] glyphosate is the only [treatment] option.”


Tanglefoot ™ is a barrier treatment for crawling insects. Photo:

Insect Barriers

A homeowner called the AgCenter to ask about a practice to protect her pecan trees from the walnut caterpillar (WC). She described using a rope soaked in oil and tying it around her tree to prevent the caterpillars from crawling up her tree. She called to ask if this method is safe for her tree. The short answer is “no” because oil can penetrate the bark of a tree and cause harm. Some herbicides are mixed with oil to kill unwanted trees by breeching the bark.

A couple of methods are safer for trees and are affordable methods of protection from WC.

A product called Tanglefoot™ is wrapped around a tree, and the caterpillars stick to it until there are so many worms that the other worms will crawl over the dead bodies. Once there are so many caterpillars, then it is time to replace the Tanglefoot. It costs $10 to $20 online.

Another product called Tred-Not Slippery Caterpillar Tape™ is also attached to the tree trunk. It is the opposite of Tanglefoot because it is so slick that the worms cannot crawl up the tree. It costs about $5 online.

A homeowner shared this observation about the Tred Not Slippery Tape, “[Here is] just a note on the slippery tape. My pecan trees are old. The bark is so rough I could not get the tape to stay on and there were spaces underneath that worms could crawl under. [I] had only one tree that it is successful on.... Thankfully, the worms do not seem to be such a menace this year! Unless they are still coming😳.”

If you want to contact Working in the Landscape, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or Also, you can be on the “commercial horticulture” 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.”

7/8/2020 5:27:52 PM
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