Beneficial Microbes for Crops: Colossus
Colossus is a beneficial microbial product for agriculture containing Streptomyces nigrescens strain MR541. This microorganism colonizes plant roots and foliage and produces beneficial byproducts that support plant vigor, growth, and yield. See the catalog recommendations and product label directions below for soil, foliar, and seed applications.
- EPA Registered
- OMRI Listed
- Lab Tested
Why Choose Colossus?
The Colossus microbe was discovered in an Idaho potato field during a
lengthy search for beneficial soil microbes in the Pacific Northwest. It stood
out among the thousands of isolates for its ability to colonize plants’ roots
as well as its production of a myriad of beneficial secondary metabolites.
Yield Maximization
Boosts crop production significantly through enhanced nutrient uptake pathways and improved metabolic efficiency.
Root Architecture
Promotes deeper, more complex root systems for better stability and access to deep-soil water reserves.
Stress Resilience
Fortifies plant cell walls against drought, heat, and environmental stressors, reducing crop loss.
- THE SCIENCE
Bio-Active Microbial Action
Colossus utilizes a proprietary strain of Streptomyces nigrescens (MR541) that actively colonizes both the rhizosphere and plant foliage. Once established, this microbe synthesizes enzymes like chitinase to enhance soil health, along with high levels of siderophores—compounds that unlock bound iron and essential metals to make them immediately available to the plant.
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Root & Foliar Colonization
Streptomyces nigrescens actively colonizes both the rhizosphere (roots) and foliage to drive plant vigor. -
Nutrient Availability (Siderophores)
Produces siderophores to unlock Iron and essential metals (Zinc, Boron, Manganese) that are typically bound in soil.
Supported Crops
Directions for Use
Foliar Application
Catalog recommendation: use 3-9 oz of Colossus per acre per foliar spray.
- For outdoor foliar applications, the product label specifies 10-150 gallons of water per acre.
- Consult the product label for application-specific directions.
Soil Drench / In-Furrow
Catalog recommendation: use 3-6 oz of Colossus per acre for soil applications.
- Apply in-furrow directly on the seed piece at planting.
- Follow-up applications can be made through irrigation or as a soil application just before a rain event.
- Apply at planting and up to two more times during the growing season.
The product label gives separate crop-specific initial and follow-up soil rates; consult the label for those directions.
Seed Treatment
Seed spray or slurry coating, per the product label.
- Prior to planting, dissolve 1-6 oz of Colossus in 1-4 oz of water per 100 lb (cwt) of seed and spray directly on seed.
- Use mist-type commercial seed treatment equipment, slurry, or comparable methods that provide thorough coverage of treated seed.
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Application Rates
Recommended rates from the Colossus catalog brochure:
| APPLICATION | METHOD | RATE / ACRE |
| Soil | In-furrow / soil application | 3-6 oz |
| Foliar | Foliar spray | 3-9 oz per spray |
Apply soil treatments at planting and up to two more times during the growing season, as described in the catalog. The product label includes additional crop-specific rates, including 1-3 oz/acre for initial soil applications on agronomic field and row crops, and separate greenhouse, nursery, hydroponic and seed-treatment directions. Consult the label for the applicable use.
