Prospects of Biological Control of Plant Diseases in Ghana: A Mini-Review

Ghana is an Agrarian country with its population dependent on agriculture for livelihood. Agriculture in our country is basically rain-fed and the use of technology is virtually nonexistent. Biotic stress accounts for about 35% yield reduction mainly through pests and diseases during production. To bring these agents under control, illiterate farmers with no knowledge in plant protection use any available means including chemical pesticides to control these biotic factors without considering their effect on human health and the environment. They tend to not only abusing these synthetic pesticides but also misusing them and at the mercy of the environment and human health. Even though these chemicals are effective, quicker and reliable [1], but they are not without side effects. Biological control of diseases caused by plant pathogens compared to chemical control or biological control of insect pests are not fully developed and exploited even though more research and effort are being invested due to its high potential. Currently, countries such as the USA, Australia and New Zealand are using commercially available biological control products [2,3]. Biological control offers safer and environmentally friendlier control option. In this mini-review, light is thrown on the prospects of biological control option as an alternative to chemical control of plant diseases in Ghana.

In the last decade, efforts are being made to shift from chemical control to biological control using microbial antagonists. Biological control is the use of an antagonist (a whole or its parts), its metabolic secondary waste to prevent, protect or control plant diseases. Biological control uses several mechanisms such as antibiotic production, inducing resistance in the host, competing for limited resources, parasitism, and promoting plant growth thereby protecting the plant from pathogens attack [4]. Not much success has been achieved in the area of biocontrol technology in Ghana since there is no policy on the part of the government to focus and direct scientists into this area of bioengineering and biotechnology. This does not also mean nothing at all has been done in this area, there are therefore few examples of the use of biocontrol agents either in a controlled environment or in the field. One such example is a pioneering role of Attafuah [5] using Pseudomonas aeruginosa (Schröter) Migula against Phytophthora palmivora, the causal agent of cacao black pod rot disease. This was followed by Odamtten, et al. [6] using Aspergillus niger and Trichoderma viride also against the cacao black pod pathogen.

Akrasi et al. [7-9] have also shown that given the needed attention and support, native rhizobacteria can be exploited for the control of plant diseases, especially for fungal cacao diseases. Much attention is being focused on cacao fungal diseases since cacao is the main backbone of the Ghanaian economy and fungal diseases are the main problem confronting the industry. Currently, there is a serious focus on the part of Larbi-Koranteng et al. [9] trying to change the direction of plant diseases management in Ghana using the biocontrol option. The approach is on using modern techniques in molecular biology, computing, analytical chemistry and statistics to enhance the future of biocontrol engineering. This perspective is concentrating on defining new techniques that will be able to characterize structures and functions of biocontrol agents, pathogen variability and the host plant at the molecular, cellular, organismal as well as ecological levels to ensure that Ghanaian food becomes safer devoid of pesticides and environmental pollution.

There is no doubt about the threat of plant pathogens to crop production and food security. For that matter, diseases causing agents need to be controlled if we want to reduce their effect on yield. However, the focus has been on the use of chemical control option at the expense of other control measures which are safer and environmentally friendlier. Control measures based on the use of this option is biocontrol engineering to manage crops from pathogens attack, thereby increasing yield. There is a great potential in this field and if seriously considered, it will not only complement but also replace the over-reliance of chemical/synthetic pesticides in agriculture.

1. Adejumo TO (1997) Identification, incidence, severity and methods of control of the causal organism of false smut disease of cowpea Vigna unguiculata (L.) Walp (Doctoral dissertation, PhD. Thesis), University of Ibadan, Nigeria.
2. (2005) APS Biological Control Committee. American Phyto Pathological Society (APS), USA.
3. (2005) Database of Microbial Biopesticides. Oregon State University, USA.
4. Kloepper JW (1993) Plant growth-promoting rhizobacteria as biocontrol agents. In: Melting EB (Ed.), Soil microbial ecology: Application in agricultural and environmental management. Marcel Dekker, USA, pp. 255-274.
5. Attafuah A (1966) Black pod disease: Biological control. Annual report, Cocoa Research Institute of Ghana, Ghana, pp. 1-115.
6. Odamtten GT, Clerk GC (1985) Studies on the possible use of two soil fungi, Aspergillus niger and Trichoderma viride as biological control agents of Phytophthora palmivora and the effect of their metabolites on cocoa seedlings. Food and Agriculture Organization of the United Nations, pp. 293-301.
7. Akrasi KO (2005) Anti-microbial properties of yam rhizosphere micro-organisms and their potential use for controlling yam tuber rots. Masters dissertation.
8. Koranteng SL, Awuah RT (2011) Biological suppression of black pod lesion development on detached cocoa pods. African Journal of Agricultural Research 6(1): 67-72.
9. Larbi Koranteng S, Awuah RT, Kankam F (2020) Biological control of black pod disease of cocoa (Theobroma cacao L.) with Bacillus amyloliquefaciens, Aspergillus sp. and Penicillium sp. in vitro and in the field. Journal of Microbiology and Antimicrobials 12(2): 52-63.