Published online by Cambridge University Press: 01 December 1999
The efficacy of insecticides derived from two local plants was tested on termites infesting maize in maize–cassava–‘Egusi’ melon intercrops in two farmers' fields in south-western Nigeria during the 1989/90 and 1990/91 cropping seasons. The intercrops consisted of 40000, 20000, and 10000 maize plants/ha, with a fixed population of 10000 plants/ha of both cassava and melon. The insecticides were aqueous extracts of ripe seeds of neem (Azadirachta indica A. Juss) and the crude seed oil of Piper guineense Schum And Thonn, each at 10% concentration at the rate of 390 litres/ha and 18 litres/ha, respectively. On the plots treated with these natural insecticides, damage by termites [Microtermes spp., Macrotermes bellicosus Smeathman = nigeriensis Sjostedt and M. subhyalinus Rambur (Isoptera: Termitidae)] was significantly lower and maize yields higher than on the control plots. The mean percentage of maize stems attacked by termites (considering all categories of termite damage) in untreated plots during the trials ranged between 0–22% in 1989 and 2–46% in 1990. Planting densities did not significantly influence termite attack on maize. Cassava and melon plants or cassava tubers were not attacked by termites in any of the trials and their yields were not affected by insecticide treatments or planting density of maize.