You’ve probably never thought about life in the soil, but it’s a jungle down there with organisms fighting each other for survival.
Instead of fighting tooth and nail, they fight by parasitizing each other and producing chemicals that help them compete with other microbes.
The genus Streptomyces is known for its production of antibiotics, making the species excellent competitors in the soil.
Photo via CDC/Dr. David Bird (PHIL#2983), 1972.
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Modern medicine has taken full advantage of the many antibiotics produced by these organisms, and more than two-thirds of the antibiotics used today were originally discovered by Streptomyces.
In recent years, these organisms have been used in agriculture to defeat plant pathogens.
Streptomyces lydicus is one such species – an ever-present soil microbe that has been studied for over 50 years.
One species in particular, WYEC 108, has been studied extensively for its ability to control a variety of root-rot-causing fungi and foliar pathogens, such as rust and gray mold.
This guide describes how this microbial fungicide works and how to use it in your garden.
From an English field to commercial use
Streptomyces lydicus strain WYEC 108 was originally isolated from an agricultural field in England. Its use in controlling pathogens has been extensively studied.
These bacteria are very effective in colonizing plant roots. They are prominent members of the rhizosphere – the area of soil that surrounds the roots of plants.
The plants release a number of nutrients into the soil, including sugars and vitamins. The microbes in the rhizosphere live on these nutrients and in return help the plants grow.
Actinovate® lawn and garden fungicide (Streptomyces lydicus strain WYEC 108)
This strain of Streptomyces is so effective at improving plant health that the bacteria are members of the group known as plant growth-promoting rhizobacteria (PGPR).
The formulation of WYEC 108 known as Actinovate is available from Arbico Organics. It is sold to control pathogens on ornamental plants, greenhouse and nursery crops, and sod.
How Streptomyces lydicus defeats fungal pathogens
Strain WYEC 108 uses several mechanisms to control pathogenic fungi. One of the ways it does this is by parasitizing the fungi.
Most fungal cell walls are composed of a polymer called chitin. This strain of Streptomyces produces an enzyme called chitinase that breaks down the cell walls of fungi, leaving the fungi vulnerable to parasitism.
Another way it outperforms the fungi is by depriving them of nutrients. Iron is an essential nutrient found in very small amounts in the soil.
WYEC 108 produces compounds called siderophores that are very effective at binding iron. The bacteria can use this iron, but it is unavailable to the fungi, which then starve. In this form, however, the plants can use it well!
Fungal pathogens controlled by Actinovate
Actinovate acts as a fungicide, fighting a range of pathogens that regularly colonize plant roots to cause root rot and damping off.
A partial list of the soil pathogens that control these bacteria includes Fusarium, Pythium, Phytophthora, Rhizoctonia, Sclerotinia, Verticillium, and Geotrichum.
In addition, Actinovate can control such leaf-dwelling pathogens as powdery mildew, downy mildew, botrytis, blight, rust, bacterial spot and black spot.
This organism is sold as a powder that is soluble in water. You can apply it to sod or potted and greenhouse plants as a drench or mixed with soil.
Follow label directions, but a common amount is one gallon per cubic foot of soil mix.
You can also spray Actinovate on the leaves of your plants every 7-14 days, depending on how badly infected your plants are.
The bacteria will only protect the leaves you spray them on, so as your plants grow, you’ll need to reapply it.
If you spray sod, you are typically reapplying the bacteria every 6-8 weeks.
It is better to apply Actinovate several times at lower rates than once at higher rates. UV light breaks down the bacteria, so it’s best to apply them in the evening or morning or on cloudy days.
This formulation is typically stable for one year when stored in its original packaging.
Find more information on uses and applications at Arbico Organics.
These bacteria are safe to use
S. lydicus is advertised as being safe for humans and is commonly found in soil where humans are regularly exposed to it. The organism is considered by scientists and researchers to be non-toxic, non-pathogenic and non-irritating.
Extensive studies of its effects on rats, fish and honeybees prior to its registration as a pesticide with the Environmental Protection Agency (EPA) indicated that the bacteria do not affect non-target organisms such as beneficial insects.
The EPA requires applicators to wear long-sleeved shirts, pants, waterproof gloves, and a filter mask when applying Actinonovate in a greenhouse. Read more about spraying techniques and safety here.
S. lydicus is safe to use with other soil inoculants, such as mycorrhizae and Trichoderma.
This common soil organism prevents many fungal diseases
Because of its ability to colonize plant roots and outcompete other microbes, Streptomyces lydicus is an excellent biological control agent.
These bacteria can be applied to your lawn and ornamental, potted or greenhouse plants. Because they only affect microbes, Actinovate is a safe compound to add to your arsenal of pathogens.
Have you used Actinovate to fight pathogens? If so, let us know how it went in the comments.
And if you’re eager to discover more of the magic of biofungicides, check out some of these guides:
© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our Terms of Service for more details. Top photo via GGD/Dr. David Bird (PHIL #2983), 1972. Product photo via Novozymes.