PlantShield - Trichoderma harzianum, strain T-22

Rootshield® Plus - WP Trichoderma harzianum Rifai strain T-22 & Trichoderma virens G-41

Rootshield® Plus - WP
Trichoderma harzianum Rifai strain T-22 & Trichoderma virens G-41

 Trichoderma atroviride (Strain LU132)

 Trichoderma atroviride (Strain LU132)

Trichoderma spp.

Trichoderma spp. are fungi that are present in nearly all soils and other diverse habitats. In soil, they frequently are the most prevalent culturable fungi. They are favored by the presence of high levels of plant roots, which they colonize readily. Some strains are highly rhizosphere competent, i.e., able to colonize and grow on roots as they develop. The most strongly rhizosphere competent strains can be added to soil or seeds by any method. Once they come into contact with roots, they colonize the root surface or cortex, depending on the strain.

In addition to colonizing roots, Trichoderma spp. attack, parasitize and otherwise gain nutrition from other fungi. Since Trichoderma spp. grow and proliferate best when there are abundant healthy roots, they have evolved numerous mechanisms for both attack of other fungi and for enhancing plant and root growth.

There are 2 different species of trichoderma typically used as biocontrols, harziamum and viride.

Trichoderma harziamum Trichoderma harzianum is a fungus that is also used as a fungicide. It is used for foliar application, seed treatment and soil treatment for suppression of various disease causing fungal pathogens. It is commonly used to treat Botrytis and Fusarium.

A few select strains of T. harzianum have been shown to suppress plant pathogens. However, they are limited in the scope of plants they protect and the pathogens they control. For example, one strain can control Pythium and grow in cooler soils, while another can control Rhizoctonia and colonizes the root system. To overcome these limitations, researchers at Cornell University produced a hybrid strain that had enhanced attributes of the parents. The strain, T-22, protects the root system against Fusarium, Pythium and Rhizoctonia on a number of crops including corn (field, sweet, silage), soybeans, potatoes, tomatoes, beans (green and dry), cabbage, cucumbers, cotton, peanuts, turf, trees, shrubs, and other transplants and ornamental crops. T-22 is able to grow in a range of soil types at temperatures above 50ºF. Because of its superior attributes, T-22 has been commercially developed as one of the first biofungicides. Several mechanisms allow T-22 to control various plant pathogens. The biofungicide protects the plant by establishing itself on the outside of the root system in the rhizosphere (root zone). Because it is a living organism, T-22 can grow along the entire length of the root system where it establishes a barrier against pathogen attack. As long as the root system remains active in its growth and development, T-22 will continue to grow along with it by feeding on the waste products released. These waste products can also serve as a meal for pathogens. Early applications of T-22 protects plant roots by removing secreted nutrients that pathogens might use. Occupation of the roots by T-22 does not seem to interfere with the activity of mycorrhizae or nitrogen-fixing Rhizobium. T-22 has been granted an exemption from the need for a tolerance by the US-EPA and is approved for use in certified organic production in several states. Its effectiveness against a range of pathogens on a diversity of plants allows it to be a part of many integrated pest management programs. T-22 can protect plant parts (roots) not previously protected by chemical fungicides. It can be used at the time of planting as a seed treatment.

Trichoderma viride The mycelium of T. viride can produce a variety of enzymes, including cellulases and chitinases which can degrade cellulose and chitin respectively. The fungicidal activity makes T. viride useful as a biological control against plant pathogenic fungi. It has been shown to provide protection against such pathogens as Rhizoctonia, Pythium and even Armillaria. It is found naturally in soil and is effective as a seed dressing in the control of seed and soil-borne diseases including Rhizoctonia solani, Macrophomina phaseolina and Fusarium species. When it is applied at the same time as the seed, it colonizes the seed surface and kills not only the pathogens present on the cuticle, but also provides protection against soil-borne pathogens.

Target Pathogens: Pythium, Rhizoctonia, Fusarium. *Strain Specific (will update with new strains and target pathogens)

Mode of Action: T. harzianum, strain T-22 utilizes several methods to suppress fungal diseases. First, it forms a physical bond with the root system of the plants, establishing itself in the rhizosphere (root zone) and thereby preventing other pathogens from colonizing the soil. This bond and continual growth of the T. harzianum throughout the root system forms a physical barrier to plant pathogens. T-22 also feeds on excess nutrient content left unused by the root system, which would provide a food source for incoming pathogens otherwise. Keeping that in mind, T. harzianum does not interfere with mycorrhizae activity or Rhizobium (a common nitrogen-fixer).

Secondly, T-22 releases chitinases, specific enzymes that denature chitin, to break down the cell wall of fungal pathogens in the soil. The holes in the cell wall created by the enzymes turn the pathogenic fungi into prey for other soil microorganisms. The combination of these methods allows T. harzianum to displace other organisms from the soil and the root system to develop additional biomass useful in increasing plant yields.

Application Tips: This product can be used in conjunction with certain other fungicides, see label and other online resources for details.

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.

Selected References

Appl Microbiol Biotechnol. 2010 Jul; 87(3): 787–799. Biology and biotechnology of Trichoderma André Schuster and Monika Schmoll.

G. E. Harman, Cornell University

Trichoderma: A significant fungus for agriculture and environment. Rajesh R. Waghunde, Rahul M. Shelake and Ambalal N. Sabalpara.

Biological control of foliar pathogens by means of Trichoderma harzianum and potential mode of action