Influence of Maize, Cowpea and Sorghum Intercropping Systems on Stem-/Pod-Borer Infestations

Abstract

The paper which covers a two season study from 1981 through 1982, major and minor cropping seasons, describes an improved methodology of sampling for stem-/pod-borer pests within an intercropping farming system involving maize, cowpea and sorghum as target crops. The authors’ approach to the intercropping study has been from a holistic angle in an attempt to gain an understanding of the processes which lead to intercropping advantages under the different cropping patterns. The target pests reported were categorized into three trophic levels: firstly, specialist feeders which were Maruca testulalis (Geyer) on cowpea and Atherigona seccata (Rondani) on sorghum; secondly, the relative specialist feeders as Chilo partelhts (Swinh.), Busseola fusca (Fuller), Eldana saccharina (Wlk.) and Sesamia calamistis (Hmps.) on maize and sorghum; and thirdly the generalist feeders represented by Heliothis armigera (Hbn.) which subsists on cowpea, maize and sorghum plants respectively. The entomological data assayed included levels of borer attack on plant spatial and temporal patterns. The population of C. partellus, the dominant stem-borer within the study area was significantly regulated within the intercropping systems. The borer incidence on the maize and sorghum monocrops and the maize/sorghum dicrop was earlier (>14 days after germination, DAG) and accentuated with time, whereas intercropping of the cereals with non cereals caused significant delay (>42 DAG) in the borer colonisation and establishment within the intercropping systems. Incidence of ‘dead hearts’ caused by the borers was significantly higher (P < 0.05) within sorghum than maize stands; a factor related to the significantly higher borer attacks on late tillers which suggest that plant ventrical heights within stands influenced borer attacks. Sorghum shootfly was restricted to within 42 DAG and very much regulated by intercropping. Maruca testulalis attack on cowpea plants was confined between 30 through 60 DAG of cowpeas. Presence or absence of non-preferred cereal hosts within the cropping patterns did not seem to interfere with the M. testulalis colonisation and establishment processes within the cropping patterns. Pod damages resulting from Maruca attack were however influenced by the cropping patterns with mixed maize-cowpea-sorghum intercrop, producing significantly higher healthier pods. The paper concludes that some intercropping patterns have many advantages over monocropping patterns with respect to pest colonisation and establishment.