Outbreak of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera : Noctuidae) on transplanted sorghum in the Far North Region of Cameroon

Abstract

Sorghum is the fifth most cultivated cereal crop in the world while in Cameroon, it ranks second after maize. Its production is hampered worldwide by various constraints including insect pests amongst which lepidopteran are predominant. Serious attacks on transplanted sorghum panicles were reported during the year 2023 in the Far North Region of Cameroon and wrongly attributed to Spodoptera frugiperda - although it is initially known to damage sorghum foliage. Field investigations were carried out with the objectives to evaluate the extent of the damages on sorghum panicles, readily identify the insect species responsible of the alarming damages and identify others insects associated with sorghum panicles. Group discussion was made with agriculture extension agents and farmers then, 30-60 sorghum plants randomly selected along two diagonals of a delimited field portion were evaluated for pest incidence and damage severity on panicles. The plague occurred in three Divisions among which Diamare was the highly affected area. This phenomenon was never reported in the past according to farmers. Pest incidence, density and severity varied across visited fields. Damages on panicle included mostly empty or unfilled grains and destroyed grains. Helicoverpa armigera Hübner was identified as the insect responsible of the alarming damages. This is the first report of H. armigera outbreak on sorghum in Cameroon. Implications of this first-time outbreak are discussed and more investigations are needed to clarify this sudden abundance of H. armigera on sorghum panicle. Three others Lepidoptera species and five bugs species emerged from panicles. The impact of sap sucking bugs on the sorghum production deserve more attention in the future.