Roots, Shoots, Fruits & Flowers: Soil Testing, Cowpea Aphids, Fig Rust & Southern Watergrass


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

Soil Testing

Brenda of Hornbeck wants to be a successful gardener and want to know, “Where do we get soil testing kits? Our veggie garden is sick and killing our plants. We need to find out what is wrong and how to repair it. Thank you for your help!”

Gardeners and homeowners can obtain soil test kits at the local AgCenter office in each parish, and some garden centers will also have these kits. Gardeners can sample the soil from their flower beds, vegetable gardens, from under fruit and shade trees, and from their lawns. The kits are in USPS Priority Mail 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.


Severe infestation by cowpea aphids. Photo: Clemson U./USDA Coop Extension Slide Series.

Cowpea Aphids

Richard in Vernon Parish contacted the AgCenter about his purple hull peas and asked what black insect were infesting his pods.

Richard has cowpea aphids, and aphids are tiny, soft-bodied insects which suck sap from plants and weakens them. Aphids withdraw more sap than they can use so they excrete the surplus fluid as honeydew. Sooty mold then infects the honeydew and causes plants to have a black appearance. If a gardener has sooty mold, then aphids would be the likely problem.

The AgCenter recommends these control measures for aphids:

  • Use slow-release nitrogen fertilizer sources to avoid rapid and excessive flushes of new growth.
  • Insecticidal soaps and oils should be considered when a pesticide is required. These soaps and oils are effective against aphids and are the least toxic to people and the environment.


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

Fig Rust

Susan 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 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.”

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.”

6/30/2020 8:52:49 PM
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