By Prof Arun Tiwari
Pests and diseases are significant challenges in agriculture, impacting crop yield, quality, and overall farm economics. Three common insect pests are aphids, caterpillars, and whiteflies. Aphids suck sap from plants and can transmit viruses.
Larvae of moths or butterflies, as caterpillars, can cause significant leaf damage. Whiteflies cause damage by sucking sap. They often spread diseases. Microscopic worms, called nematodes, attack plant roots, reducing nutrient uptake. There are notorious and widespread locust species in Africa. They can form swarms that migrate long distances, threatening crops and pastures. Common plant diseases are fungal, bacterial, or viral.
Fungal diseases like powdery mildew affect many crops, leading to reduced photosynthesis. Rust causes orange or black pustules on leaves, affecting plant vitality. Bacterial wilt affects various crops, leading to wilting and death. Fire blight affects apple and pear trees, causing blossom and branch dieback. Viral diseases can be spread by insects or tools, leading to mottled leaves and stunted growth. Pests and diseases can significantly reduce the quantity of produce.
Infestations can affect the quality of crops, making them less marketable. The economic burden is significant in harvest losses. Fall Armyworm (Spodoptera frugiperda) is a highly destructive caterpillar that attacks maize, sorghum, and rice crops in Africa, causing up to 70-100 percent yield loss in severe infestations.
Spider mites can damage cotton and other crops by feeding on plant sap. Striga (witchweed) is a parasitic plant that attaches to the roots of cereal crops and is more problematic in low-nutrient soils.
A combination of viruses (such as the Maize chlorotic mottle virus or MCMV and the Sugarcane mosaic virus or SCMV) and the presence of the corn leaf aphid cause yellowing of leaves, stunted growth, and tip necrosis, leading to 100 percent yield losses of maize, which is a staple crop in many subSaharan countries.
Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD) reduce both yield and the market value of cassava, posing a significant threat to food security Biotechnology can be used to develop crops with enhanced disease resistance, leading to decreased reliance on fungicides and other chemical treatments. Crops such as Bt cotton and Bt corn are genetically engineered to express proteins from the bacterium Bacillus thuringiensis, which are toxic to specific pests and significantly reduce the need for chemical insecticides.
Genome editing techniques like CRISPR/ Cas9 allow scientists to modify plants to enhance traits such as pest resistance, reducing the need for chemical pest control. Markerassisted selection helps breeders select plants that are resistant to pests and diseases.
However, global corporations protract these technologies and are not available for wide use. Biological control methods involve using natural organisms or substances derived from them (such as bacterial or fungal pathogens) to combat pests. These biopesticides can be highly specific, meaning they target pests without harming beneficial insects or the environment.
Products derived from beneficial microorganisms can help suppress pest populations and promote plant health. In India, oil extracted from the seeds of the neem tree (Azadirachta indica) disrupts pests’ life cycles. Pyrethrin derived from the flowers of the chrysanthemum plant is effective against a broad range of insects, including aphids, beetles, and flies. Smallholder farmers often need proper protective equipment to handle pesticides, raising health risks. Biopesticides are typically less toxic, reducing health hazards for farmworkers and their families.
Specific biopesticides (like Trichoderma spp. and Bacillus subtilis) can improve soil health by promoting beneficial microorganisms that suppress soilborne pathogens and enhance plant growth. Biopesticides provide a promising solution for smallholder farmers looking to manage pests sustainably and economically. By reducing dependency on chemical pesticides, improving health and safety, and enhancing soil quality, biopesticides can contribute to more resilient agricultural systems and greater food security in smallholder farming communities.
Educating farmers about these products and ensuring their accessibility is crucial to maximising their benefits. While biopesticides have significant potential to transform pest management and promote sustainable agriculture, addressing the abovementioned barriers is crucial. This may involve enhancing regulatory frameworks, providing support for education and training, ensuring market access, and fostering collaboration among stakeholders, including governments, researchers, farmers, and the private sector. Science must be locally done and applied.
That is what is needed most. Overcoming these challenges requires a concerted effort to build awareness, trust, and capacity to use biopesticides as a viable solution for pest management. One of the main problems limiting the production of biopesticides is the standardisation of plant material and the stable availability of bioactive compounds. It is time to wake up and usher in Africa’s Biopesticide Revolution, helping smallholders earn revenue by exporting to markets conscious of chemical pesticides in their food chains.
Prof Arun Tiwari is an Indian missile scientist, author, and professor.