By Gift Briton
With fall armyworm (FAW) causing annual yield losses of up to USD 9.4 billion in Africa alone, significantly impacting household income and food security, experts call for further research on the management of the pest and its relationship with the environment in order to minimize impacts on invaded regions.
According to a Centre for Agriculture and Bioscience International (CABI)-led study, the pest is highly fertile with a short generation time, good dispersal capacity, and rapid development of insecticide resistance in insecticide-exposed populations, thereby making the current management and control strategies incomplete.
Originating from America and first spotted in west Africa in 2016, FAW has invaded most territories worldwide including most parts of sub-Saharan Africa, Asia and Europe, feeding on more than 350 plant species including economically important agricultural crops such as maize, rice, millet, soybean, cotton and sorghum among others.
According to the researchers, current management strategies for FAW in America where the pest originated rely mainly on broad-spectrum chemical insecticides and genetically-engineered crops. However, these options are considered undesirable and not sustainable in many invaded countries.
To develop and implement sustainable integrated pest management (IPM) that is appropriate for each invaded region, the authors recommend further research on the pest’s management and ecology, including identifying region-specific pheromones (traps used to monitor the target pest) because pheromones that are currently available for the management are not specific enough for monitoring FAW, especially in areas that are not yet invaded.
Furthermore, with the spread of FAW already mapped using various models, the researchers note that it will be important to model the seasonal spread and impact of migrating populations for temperate countries in Europe, Asia, and Oceania.
The authors further note that because high FAW populations and severe leaf damage do not necessarily result in severe yield losses, building meaningful IPM strategies, will be helpful to better understand the relationship between FAW infestation, leaf damage, ear damage, and yield loss, and how these relationships vary with crop stage and agroecological conditions, including the abundance or efficacy of natural enemies.
They have also prosed the development of methods for augmentative biological control with local parasitoids, predators, and entomopathogens (pathogens that kill or seriously disable insects) in invaded areas, as well as agroecological approaches, to enhance the effectiveness of natural enemies already present in the system, adding that cost-effectiveness needs to be considered, considering the low value of the main crops affected by FAW.
More importantly, the report notes that agroecological approaches to FAW management should be given more attention, with specific studies in different agro-ecological zones in both the invaded and native ranges also suggesting an assessment of the impact of chemical insecticides and other current control methods on natural enemies and the environment to improve IPM for FAW.
Moreover, with studies showing that most farmers in developing countries rarely use protective clothing, social studies on the impact of chemical insecticides on farmer health and the well-being of farming communities are also urgently required.
Though genetically-engineered Bt maize, is used extensively against FAW especially in America, due to for various reasons, genetically-engineered crops are not considered acceptable by most invaded countries. Therefore, the authors urge that the sustainable use of Bt maize for managing FAW should be a priority research topic.
According to them, the recent evidence of new introductions of foreign FAW into Africa emphasizes the need for continued surveillance at entry points to limit the introduction of FAW populations with broader host range and resistance traits, adding that socio-cultural studies are necessary to better understand how to develop culturally appropriate IPM recommendations and for improved communication of technologies.