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Streptomyces spp.

Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomycetaceae. Over 500 species of Streptomyces bacteria have been described. As with the other Actinobacteria, streptomycetes are Gram-positive, and have genomes with high GC content. Found predominantly in soil and decaying vegetation, most streptomycetes produce spores, and are noted for their distinct "earthy" odor.

It is known that antagonistic activities of bacteria against fungal pathogens can be achieved through three main mechanisms: competition for nutrients and space, antibiosis, and parasitism (Gonzalez-Franco and Robles-Hernandez, 2009; Boukaew and Prasertsan, 2014). The advantages of Streptomyces spp. include their ability to colonize plant root surfaces, survive in various types of soil and also produce spores which allow them to survive longer and in various extreme conditions (Gonzalez-Franco and Robles-Hernandez, 2009; Ningthoujam et al., 2009).

  1. Actinovate contains the innoculant microorganism Streptomyces lydicus strain WYEC 108 which is a naturally occurring bacterium that is commonly found in soil. When applied to soil mixes or turf grass, the bacterium protects the plant against a range of root decay fungi. Streptomyces lydicus strain WYEC 108 can also be applied to plant foliage in greenhouses to control powdery mildew.
  2. Forge SP contains the innoculant microorganism Streptomyces nigrescens MR541 . Forge SP is a high concentration of a unique beneficial microorganism that naturally complexes iron, making it more available to plants.
  3. Developed from a naturally occurring bacteria, Streptomyces griseoviridis, Mycostop Biological Fungicide thrives in the root zone of plants. When applied as a drench or spray the dried spores and mycelium of the Streptomyces culture in Mycostop germinate and begin to grow on and around the plant roots. In doing so they create a biological defense against root infecting pathogenic fungi which cause disease such as wilt and root rot.

Target Pathogens: Root decay fungi such as Fusarium, Rhizoctonia, Pythium, Phytophthora, Phytomatotricum, Aphanomyces, Monosprascus, Armillaria, Sclerotinia, Postia, Verticillium, Geotrichum. Other target pests include powdery mildew and other fungal pathogens that attack plant foliage.

Mode of Action: The mode of action of active substance is by competitive exclusion of the pathogen and by production and secretion of antifungal metabolites. Streptomyces lydicus strain WYEC 108 is a naturally occurring bacterium that is commonly found in soil environments. It is thought that the bacterium works by colonizing the growing root tips of plants and parasitizing root decay fungi (such as Fusarium, Pythium, and other species). The bacterium may also produce antibiotics that act against these fungi. Fungal cell walls often contain chitin as a major component; chitinases are well known to fungal cell walls.  Streptomyces lydicus WYEC108 was shown to pro- duce a very high level of chitinase when grown in the presence of fungal cell wall chitin, specifically with chitins prepared from the walls of an Aphanomyces sp. and of P. ultimum. The chitinase produced was active against the fungi P. ultimum and Rhizoctoniu soluni as measured by the release of sugars from their cell walls.

S. lydicus colonizes growing root tips of plants and acts as a mycoparasite of fungal root pathogens which helps protect the plants. Other possible mechanisms include the production and excretion of antifungal metabolites (e.g., antibiotics and/or low molecular weight antifungal compounds or lytic enzymes like chitinase) after colonization. (EPA)

Application Tips: For best results, treat prior to foliar disease development or at the first sign of foliar disease infection. Repeat at 7-day intervals or as needed. Under conditions of high disease pressure, shorten the spray interval or use the higher rate.

Streptomyces becomes active in soil or on the plant foliage when the temperatures are above 45°F and is not effective when temperatures remain cold. Can be applied to sterilized or fumigated soil, but it must be applied after sterilization or fumigation active ingredient has dissipated.

Precautions and Safety Equipment: Minimize your exposure to pesticides.  Avoid contact with eyes.  Wear eye protection, long pants, a long-sleeved shirt, and a hat that can be washed after each use.  Always read label of individual product for additional directions.

Personal Protective Equipment (PPE):

Applicators and other handlers must wear:

• Long-sleeved shirt and long pants,
• Shoes plus socks

Mixer/loaders must wear a dust/mist- filtering respirator meeting NIOSH standards of at least N-95, R-95, or P-95. Repeated exposure to high concentrations of microbial proteins can cause allergic sensitization. Follow manufacturer’s instructions for cleaning/maintaining PPE. If no such instructions for washables, use detergent and hot water. Keep and wash PPE separately from other laundry.

Selected References

Properties of the chitinase of the antifungal biocontrol agent Streptomyces lydicus WYEClOS. Brinda Mahadevan and Don L. Crawford. Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, Idaho, U.S.

INTERNATIONAL JOURNAL OF SYSTEMIC BACTERIOLOGY. JULY 1995. P. 507-514. A Taxonomic Study of the Genus Streptomyces by Analysis of Ribosomal Protein AT-L30. KOZO OCHI. National Food Research Institute, 2-1-2 Kannondai, Tsukuba, Ibaraki 305, Japan

EPA. BIOPESTICIDE REGISTRATION ACTION DOCUMENT STREPTOMYCES LYDICUS WYEC 108 (PC Code 006327)

Gonzalez-Franco C., Robles-Hernandez R. (2009). Actinomycetes as biological control agents of phytopathogenic fungi. Tecnociencia Chihuahua 3 64–73.

Boukaew S., Prasertsan P. (2014). Suppression of rice sheath blight disease using a heat stable culture filtrate from Streptomyces philanthi RM-1-138. Crop Protect. 61 1–10. 10.1016/j.cropro.2014.02.012 [Cross Ref]