Cassava is the third largest source of carbohydrate in the world, coming behind only rice and maize. It is a staple crop that feeds at least 300 million Africans alone and is being commercialized heavily these days because of its growing importance industrially.
As a widely grown in Africa, Asia, and Latin America, it provides food security and income to farming communities. Though the crop is tolerant of heat and some harsh weather conditions, it is highly susceptible to crop pests. The crop’s low productivity in Africa (8.8t/ha), which is less than the global average (10.98t/ha), is mainly due to activities of numerous insect pests and diseases. The most challenging of these insect pests is Bemisia tabaci, otherwise called Gennadius or white fly, which feed directly on the plant’s sap. They also serve as vector for other cassava diseases. The challenge posed is due to multiple biologically distinct species within the species complex that cannot be readily differentiated due to the lack of distinct morphological characters.
Overuse of pesticides and rapid development of resistance in B. tabaci has been shown to cause high abundance and change the identity of the common B. tabaci species in other cropping systems around the world. Given that cassava is a crop with a relatively long growth season (compared with many vegetables), and now receives relatively little pesticide applications, it is important to explore the potential impact of natural enemies. Furthermore, the integration of natural enemies with other management options (e.g. host-plant resistance and habitat management) is critical. A strong case can therefore be made for the use of biopesticides and for good reasons. It is also very important to quantify the scale at which natural enemies may have an impact (i.e. within a few tens of metres or within 100 m of a source field), so as to make specific management recommendations to farmers. It is safe to mention at this juncture that the use of biopesticides is only recommended as a key part of the wider and more sustainable integrated pest management model. Microbial pesticides is recommended here as they are natural enemies of insect pests, pest specific and do their job without harming the crop, environment or people through contamination.
Adopting this approach will significantly reduce the huge economic loss incurred as a result of diseases spread by whiteflies especially cassava mosaic virus which in East and Central Africa is estimated to be between US$1.9 billion and $2.7 billion annually. This figure would otherwise be sufficient to lift millions of people out of poverty permanently, achieve food security and provide critical infrastructures.
Femi Gabriel Oyeniyi, Nigeria