Trichoderma is a cosmopolitan non toxigenic fungi found in the soil. It has attracted significant attention from farmers and scientists across the globe due to its effective antagonism activities against soil borne pathogens and diseases as well as growth promotion. The mechanisms used by Trichoderma species are competition, mycoparasitism and production of hormones which promote growth (Sharon et al. 2011, p. 188).
Trichoderma is a natural product hence poses minimal negative effects to the environment, useful microorganisms and human beings unlike the synthetic products yet it is more cost effective due to its availability in nature (Sharon et al 2011, p. 190).
Proved effectiveness of Trichoderma against Fusarium
Fusarium which is a widely distributed soil fungi has been identified as the a significantly frequent soil borne pathogens leading to huge economical losses in the agricultural sector (Saremi et al. 2011, p. 83395).
In Kenya, tomatoes and bananas are the most affected by the soil borne pathogen Fusarium. Fusarium oxysporum causes Fusarium wilt in tomatoes while Fusarium wilt in bananas is called panama disease (Oyugi 2017, p. 2). Evaluation of Trichoderma herzanium against Fusarium wilt of tomatoes which is the most common tomato disease worldwide has been carried out in several instances. This is because, Fusarium wilt must be controlled to maintain plant vigor and productivity yet the previously used methods mostly relying on synthetic products, cultural and chemical have numerous shortcomings and are also challenged by emergence of new strains of the host pathogen (Oyugi 2017, p. 2).
In vivo (green house tests) and in vitro (dual culture in laboratory) experiments were carried out by Moosa et al (2017, p. 210) to evaluate the effects of cow, horse, chicken or sheep manure and the antagonistic isolates of Trichoderma viride and T. harzianum against F. oxysporum f. sp. lycopersici on tomato. The combination of Trichoderma isolates and cow manure performed best in vivo in controlling disease incidence of Fusarium wilt of tomato. Both isolates of Trichoderma and cow manure were evaluated in vitro and in vivo individually and in combination. In vitro the T. viride and cow manure mix produced the best pathogen inhibition. In vivo the T. viride, T. harzianum and cow manure mix produced the best inhibition.
The antagonistic capabilities of eight Trichoderma isolates were carried out to test the ability of the Trichoderma species to inhibit the Fusarium wilt and promote the growth parameters of tomato seedling. In the laboratory tests (in vivo), the findings indicated that that Trichoderma isolate MiT-4 inhibited the radial mycelial growth of the pathogen by 58.4%. Under greenhouse condition (in vivo) application of Trichoderma isolate (MiT-3) reduced incidence of over Fusarium oxysporium f. sp lycopersici by 83.66%. Application of Trichoderma isolates (MiT-3) on tomato seeds, seedlings showed a significant stimulatory effect on shoot and root height by 7.53 cm and 7.1 cm respectively which was higher than the control (Babychan & Simon 2017, p. 216).
A study by (Khan et al. 2017, p. 112) comprised collection of diseased samples from rhizosphere of banana plants in the research area of National Agriculture Research Centre (NARC), Islamabad and culturing on Potato Dextrose Agar (PDA) to isolate pathogenic strains of F. oxysporium f. sp. cubense. Antagonistic potential of Trichoderma harzianum against F. oxysporum f. sp. cubense was evaluated under controlled conditions. T. harzianum produced up to 75.5% inhibition of colony growth of the pathogen followed by incubation for 72 h at 28+2°C in vitro. In pot culture (in vivo) T. harzianum considerably reduced disease severity. It proves that it is a potential biological control agent against banana wilt (panama) pathogen.
These studies prove the effectivesness of Trichoderma strains in eliminating the destructive Fusarium wilt diseases in bananas and tomatoes. Kenya is an agricultural based nation which experiences significant losses from the Fusarium wilt yet Trichoderma isolates are freely available in the Kenyan soils. Introducing Trichoderma as a biocontrol especially in combination with organic fertilizers which are also environmental friendly could act as a cost effective, environmental friendly and safe method of controlling Fusarium wilt and boosting the economic standard associated with the affected crops.
Babychan, M., & Simon, S. (2017). Efficacy of Trichoderma spp. against Fusarium oxysporum f. sp. lycopersici.(FOL) infecting pre-and post-seedling of tomato. Journal of Pharmacognosy and Phytochemistry, 6(4), 616-619.
Moosa, A., Sahi, S. T., Haq, I. U., Farzand, A., Khan, S. A., & Javaid, K. (2017). Antagonistic potential of Trichoderma isolates and manures against fusarium wilt of tomato. International Journal of Vegetable Science, 23(3), 207-218.
Saremi, H., Okhovvat, S. M., & Ashrafi, S. J. (2011). Fusarium diseases as the main soil borne fungal pathogen on plants and their control management with soil solarization in Iran. African Journal of Biotechnology, 10(80), 18391-18398.
Sharon, E., Chet, I., & Spiegel, Y. (2011). Trichoderma as a biological control agent. In Biological Control of Plant-Parasitic Nematodes: (pp. 183-201). Springer Netherlands.