Fusarium Wilt Banana Control: Biological Solutions and Sustainable Practices

I was once involved in research to find the cause of the destruction of banana crops in the tropical areas and years back I came across the fateful side of fusarium wilt in banana plantations and fusarium wilt treatment. Having to walk through fields where previously dominant Cavendish plants already showed the characteristic symptoms of Panama disease, i.e., yellowing of the older leaves towards younger ones, yellowing of the vascular tissue becoming visible in split pseudostems, and entire plants collapsing due to the vegetable disease, I could experience very intensively the insidious nature of this soil borne pathogen. The fact that Fusarium oxysporum f. sp. cubense (Foc), tropical race 4 has now become a threat to more than 80 percent of world banana production was shocking indeed. The conventional fusarium wilt banana control fungicides have not been effective with the difficulties that have made fusarium wilt banana disease control to be a topical issue among farmers. It is because of this realization that I have set out on this search to become a sustainable, biological believer in solving global challenges. Years after doing my research work, I found innovative solutions to cure fusarium wilt and control Banana disease-giving new hope to farmers the world over who are in desperate need of options to replace time tested but ineffective solutions that have lost to the virame nature of the pathogen.

Understanding the Enemy: Fusarium Wilt Disease Pathology

Fusarium oxysporum f. sp. cubense is the causal agent of one of the most damaging diseases of agriculture- fusarium wilt of banana, and the pathogenic strain known as the TR4 strain is the most recent ever-evolving threat to banana cultivation around the world. The fungus is most notorious because of its extremely high persistence in contaminated soil as it can survive up to 30 years due to the development of specialized survival structures such as chlamydospores. Fusarium oxysporum f. sp. Cubense LIFECYCLE invades the roots and the process of root infection of Fusarium oxysporum f. sp. Cubense starts with penetration of spores into the healthy banana root tissue which subsequently colonize the vascular system of the plant. The outcome of the disease process is disastrous: the primary attack involves the root infection that causes clogging of the xylem, disruption of vital delivery of nutrients and water to the plant and eventual death of the plant. The Environmental impact on Fusarium wilt because the pathogen takes several decades to die down and this makes it very hard to be eradicated. Such a price is astronomical in economic terms: fusarium wilt virtually wiped out the Gros Michel banana years ago and currently, TR4 threatens the devastating existence of the Cavendish strain, the world favorite. Recent estimations showed that there might be more than 18.2 billion of losses in the world, and one country e.g. Indonesia (121 million of losses) and another e.g. Taiwan (253 million of losses) sustain losses because of TR4. The ineffectiveness of available Fusarium wilt management options highlights the dire necessity of developing effective management approaches to Fusarium wilt and more focus should be drawn on biological control of fusarium wilt of banana as long term banana production and rural livelihoods protection strategy.

To soil amendments for disease management, fusarium wilt banana symptoms must be intercepted early in order to succeed. Externally, leaves of older generations begin to turn yellow and then gradually younger leaves are affected, wilting even with good moisture in the soil is common. More serious infections can be noted as typical pseudostem fission and collapse of plants. It is further confirmed by the occurrence of internal symptoms: frequently reddish-brown vascular discoloration seen in cross-sections of roots and pseudostems and considered a hallmark diagnostic symptom of fusarium wilt as compared to other banana diseases. During field studies, the ability of the pathogen to move around so fast by bouncing on polluted soil, irrigation water, and farm tools comes to light- emphasizing the significance of effective biosecurity practices in any plan on how to control fusarium wilt in banana. To manage this completely, modern lab approaches like molecular diagnosis are employed that identifies SIX genes linked to virulence of the pathogen so an accurate strain identification could be made. This then provides targeted soil corrections to help in the disease management as well as allow growers to be more proactive with their science-based measures to prevent the disease, as well as control them.

Traditional Treatment Approaches and Their Limitations

Findings of various researches for banana fusarium wilt management, all indicate that controlling banana fusarium wilt by application of a conventional chemical control is severely limited particularly in cases involving the hardy FocTR4 strain. Monomals like azoles, strobilurins, and benzimidazoles could induce lower efficacy with many studies reporting less than 30 percent control as pathogens would develop hardy chlamydospores that are dormant until circumstances are favorable. This in addition to the environmental factors and the declining of the export market to more stringent residue limits has rendered the chemical methods unsustainable and not economically viable especially among small scale farmers who incur the cost of repeatedly and in most cases ineffectively applying fungicides. In reaction, there is an increment in research that is pointing to the use of using effective microorganisms in managing fusarium wilt like using beneficial fungi and bacteria that act directly to suppress/compete with the pathogen. What competes with this biological method is that it is more effective and it is in line with the demands of organic production. Genetic resistance in bananas- through production of resistant varieties- is still the basis of long term or sustainable control in these systems and makes it even stronger that integrated control solutions need to be addressed going beyond one dimensional control schemes involving only chemicals.

Conducting activities of the traditional cultures has serious constraints against the incessant problem of fusarium wilt. Sustainable banana farming practices like crop rotation does little to help because the pathogen can live in soil as long as 30 years leaving that well-used disease control tool out of the tool box. Although removal of the infected plant material may temporarily help, such a method tends to deal with only above-ground infections and leaves the source of the disease, the infected soil, unchanged, leading to recurrence of the disease. Effective biosecurity measures are usually challenging to implement, especially where equipment and labor tied to transfers between farms enable transmission of pathogens within a system. Also, limited availability of resistant banana varieties which are commercially viable makes the control of the disease difficult- even though researchers have come up with resistant varieties that are tolerant to TR4, many varieties lack consumer acceptance or reduced potential in yield. This has compelled farmers to make untenable decisions between economy and disease resistance thus the necessity to investigate how to treat fusarium wilt using integrated management involving soil amendments to manage the disease and to use sustainable farming of bananas that involve the integration of cultural, biological and agronomic practices in ensuring success of such farming in the long term.

The Biological Control Revolution: Trichoderma harzianum

Trichoderma harzianum for biological control of fusarium wilt of banana comes out as a naturally occurring fungus present in the soil, with really amazing antagonistic qualities against fusarium wilt disease. This useful microorganism uses more than one biocontrol mechanism acting in synergy to inhibit the activity of the pathogen and therefore it is an essential tool in the way to control fusarium wilt in bananas. The first defence mechanism is competition in space where the fast growth rate of T. harzianum always remains ahead of pathogenic fungi such that the fungus forms protective zones around plant roots. Mycoparasitism provides the direct suppression of pathogens by means of secretion of cell wall-degrading factors, which penetrate Fusarium oxysporum f. sp. cubense (Foc) hyphae and spores. Also, antibiosis also provides a measure of defense through secondary metabolite production that is harmful to Foc, such as disruption of pathogen cellular functions. Above all, the systemic resistance triggered by biological control reduces the severity of fusarium wilt of banana attacks and predispenses banana plants to respond better to pathogen attack by increasing the increase of defense related chemicals. That is why T. harzianum is a foundation of the effective banana fusarium wilt management strategies all over the world.

There is a high level of documentation in research that confirms the efficacy of the Trichoderma harzianum for fusarium wilt treatment induced by the fusarium wilt disease. In vitro tests show that T. reesei isolate CSR-T-3 could suppress the growth of Foc TR4 by up to 85.19 per cent, which indicates a high degree of suppression of the pathogen in the controlled conditions of the laboratory. The results obtained by field trials are more promising as several studies specify that 70% of the disease control efficacy can be achieved under natural growing conditions. The mechanisms of this success can be illuminated with molecular analysis where there is a highly pronounced induction of defense enzymes 5 and 7 that occur in treated plants: 5 and 7 5-sesquirtinase, peroxidase and chitinase, which are the key proteins as they provide plant with good pathogen resistance. Moreover, in studies on the production of metabolites, there have been several antifungal compounds such as 0-caryophyllene, peptaibols and iturin C19 identified that give the best biochemical arguments as to the protection offered by T. harzianum. All these findings reinforce the need to consider the use of biological control in combination with resistant banana cultivars as intervention programs to provide long term management of fusarium wilt in banana crops.

Using Trichoderma harzianum as biological control of fusarium wilt of banana has major benefits compared to the alternative use of chemicals. The beneficial fungus does not show any toxicity even on beneficial insects, pollinators, and soil microorganisms, which qualifies it as a perfect ingredient of effective fusarium wilt banana control strategies. Since it is compatible with organic farming systems it also adheres to increasing consumer demand of residue free produce and it avoids the development of pesticide resistance. The application of T. harzianum results in no harmful residues left on banana fruits unlike synthetic fungicides used in this capacity which fail to meet stringent banana export market protocol and food safety guidelines. This gives it very bright prospects as a very viable technique in the sustainable management of fusarium wilt banana which safeguards market access and health of the crop in tandem.

Breakthrough Product Discovery: HarzShield

HarzShield for fusarium wilt treatment is a technological improvement on the technology of controlling the fusarium wilt of banana at professional level. Based on Trichoderma harzianum, this bio-fungicide has high spore concentrations of 5 x 10 -8 CFU/g, thus performing a great job in root colonization and strong pathogen suppression that is essential in successful fusarium wilt management in the state. Its wettable powder formulation makes it easy to apply in the different delivery systems such as in soil drench and drip irrigation and excellent storage stability within a 24 months life under the right conditions. This high level of formulation stability obviates the issue of loss of viability on storage and transport which is a major processing key to effective management of fusarium wilt in bananas particularly in far-flung regions where managing fusarium wilt in bananas may experience logistic difficulties. HarzShield, as part of the extensive fusarium wilt banana control, provides the growers with an effective and environment-friendly substitute of the use of fusarium wilt control fungicides in beneficial long-term health and yield of the banana crop.

Extensive testing in the field determines the efficacy of HarzShield under varying growing environments and as such, this product is a reliable remedy in the fusarium wilt banana control. Best use rates of 3kg per acre offers massive suppression on its use at planting with part of the application being done at a 10-12-week interval, which sustains the protection throughout the season. Several application modes serve different farm management systems and infrastructure potentials, i.e., soil drenching, drip irrigation, and foliar spraying. Also, crop compatibility is not restricted to bananas alone but goes across to cover citrus, vegetables and other high value crops making HarzShield a diverse product that a diversified farming operation could utilize in its offering of the biological control of fusarium wilt of banana and other environmental friendly disease management techniques.

In addition to its direct pathogen control capabilities, Biological control of Fusarium wilt with HarzShield also provides other plant health effects beyond just the direct illness management, which all lead to an overall much healthier crop performance. Through better formation of roots, uptake of nutrients and water is more effective leading to better and more vigorous banana plants. This enhances plant desirable qualities like plant vigor and stress tolerance that improves adaptation of the crops to various environmental hazards like drought, fluctuating temperatures and injury due to mechanical impacts. The health of soil is also enhanced by the presence of optimistic microbial activity to enhance the structure of soils and nutrient cycling. Besides, the possibility of combining HarzShield (fusarium wilt control fungicides) with other biocontrols agents gives the potential to develop a robust integrated biological control of the Fusarium wilt systems that addresses several plant health issues at once. This qualifies it to be an important ingredient in current fusarium wilt control fungicides practices, whereby efficacy is coupled with sustainability to ensure the success of long-term production of banana fruits.

Conclusion and Future Outlook

Trichoderma harzianum and HarzShield are an advancement breakthrough in the development of fusarium wilt banana control and management of fusarium wilt and banana as well as the future research on ways of sustainable banana farming practices in the face of destroying fusarium wilt ravages. A sustainable success can only be realized through the careful combination of the biological control with a good practice of maintaining agriculture including a good nutrition, a good management of water and a good management of biosecurity. Even more enhanced protection of the banana crops all over the world can be anticipated with the continuation of research and development of the fusarium wilt treatment and application protocols in fusarium wilt control fungicide such as HarzShield. Such inventions will assist in making sure that this crucial food security crop does not change or die out, it is there to benefit the 400 million people who need it as food and as income earners.

References:

1. Thangavelu, R., A. Palaniswami, and R. Velazhahan. “Mass production of Trichoderma harzianum for managing fusarium wilt of banana.” Agriculture, ecosystems & environment 103.1 (2004): 259-263.
2. Castillo, Arfe G., Cecirly G. Puig, and Christian Joseph R. Cumagun. “Non-synergistic effect of Trichoderma harzianum and Glomus spp. in reducing infection of Fusarium wilt in banana.” Pathogens 8.2 (2019): 43.