Fall armyworm in Africa: which 'race' is in the race, and why does it matter?
In Africa, maize is the primary host plant of fall armyworm, Spodoptera frugiperda. However, based on feeding preferences, two different races or strains of the pest, i.e. a maize strain and a rice strain, have been reported in its native range of the tropical Americas. These two strains occur in Africa as well. For instance, fall armyworm in Nigeria was found to be the rice strain, whereas the population in Sao Tome and Principe was found to be the maize strain, despite the fact that both populations severely damaged the maize crop. This paper presents studies on the genetic and physiological differences or similarities between these strains, which is important for the use of pheromone-based monitoring for fall armyworm surveillance programmes. Such knowledge also would be useful for the selection of appropriate biological control agents and chemical pesticides. For the most effective use of pheromones, it is suggested to confirm the exact identity of the strains, their pheromone composition, and the male fall armyworm moth responses to pheromone blends resembling the maize and rice-strain females in major maize-producing locations of Africa where the pest is already present.