Roots, Shoots, Fruits & Flowers: Beneficial Nematodes, Rose Gentian, Ailing Tomato Plant & Organic Fungicides


A dead flea killed by a predatory nematode.

Beneficial Nematodes

In general, RSFF addresses gardening and landscape issues seasonally as issues and questions arise. However, AHA checked the email inbox for some earlier questions. Sherry sent in her question earlier in the year, “I remembered something about [beneficial] nematodes that kill fleas and has to be applied in cool season. I thought I heard it in your [Master Gardener] class but not sure. If so, where can I purchase these nematodes locally or do, they need to be ordered?”

Nematodes are microscopic worms and are part of the living biology of the soil. These tiny worms specifically attack certain insects that complete part of their life cycle in the soil. This organic treatment is safe for people and pets because these beneficial nematodes specifically infect insects. In general, the best way to purchase products with nematodes is to go online and search for “fleas + beneficial nematodes” to find useful links. After purchasing a product, read the label about the best way to apply a nematode treatment. In general, low light conditions would be the best time to apply, and direct sunlight would render the treatment much less effective. For heavy flea infestations, several treatments may be needed.


Rose gentian, an early fall wildflower.
Photo: Lea Kimbrell.

Rose Gentian

Back in early fall, Lea sent her question with an image of a wildflower, “[I] can’t find this [plant] in my [wildflower] books? Thanks for your time.”

Lea’s pink flowers goes by the common name, rose gentian. The Missouri Department of Conservation (MDC) discusses adding this native plant to a landscape, “This showy native wildflower should be used more often in flower gardens. The plants reseed themselves and can have a permanent presence. They prefer acid soil and an open situation. Don’t dig plants from the wild; get them from reputable wildflower nurseries.” MDC adds this comment about the ecological benefits of rose gentian, “Bees, butterflies, and skippers visit the flowers, and at least a few moths or butterfly species use it as their larval food plant.”


A tomato plant with herbicide injury.

Ailing Tomato Plant

During our growing season, a gardener sent an image of a tomato plant by text message with strange symptoms.

Dr. Raj Singh, the AgCenter’s “Plant Doctor”, quickly diagnosed the issue with this tomato plant as herbicide injury from drifting glyphosate. Tomato plants are very susceptible to herbicides so spraying herbicides on a windy day is a poor decision and could damage desirable plants.


Copper fungicide dust, an organic treatment for preventing plant diseases.
Photo: Bonide(r) Products LLC.


Serenade(r) is a biological control for fungal plant diseases.
Photo: Bayer Crop Science.

Organic Fungicides

Earlier in the year when rain persisted during the winter and spring, many gardeners had complaints about diseased plants. George, an Advanced Master Gardener, uses organic products in his garden and shared this information, “Some of my tomatoes are suffering from Early Blight due to all of this terrible flooding and constant rain. Here is an article with recommendations for treatment. A newer copper dust [Bonide® Copper Fungicide Dust] to kill the pathogen, [and] then Serenade (Bacillus subtilis) for infection prevention looks like a good strategy. I am sure… you will be bombarded with questions about this tomato pathogen.”

Dr. Jenna Brackerman, a Plant Pathologist at Purdue University, affirmed copper as an organic treatment for fungal diseases, “Sulfur is the oldest recorded fungicide and has been used for more than 2,000 years. Early in agricultural history, the Greeks recognized its efficacy against rust diseases on wheat.

Although few homeowners grow their own wheat, sulfur can be a preventive fungicide against powdery mildew, rose black spot, rusts, and other diseases. Sulfur prevents fungal spores from germinating, so it must be applied before the disease develops for effective results. Sulfur can be purchased as a dust, wettable powder, or liquid.”

Serenade® is an organic, biological control for plant diseases and uses a soil bacterium with effective anti-fungal properties against a broad spectrum of fungi. The bacterium can exist in the digestive tracts of people and pets without harmful results. The red bottle on the left is a convenient, ready-to-use (RTU) formulation while the bottle on the right requires mixing and application as a spray. As always, read the labels of either conventional or organic pesticides for safe and effective results.

If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 318-264-2448 or Also, please share the name of your parish.

“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.”

12/10/2021 2:13:22 PM
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