Effects of nitrogen on stem borer damage in a sorghum/millet m ixture were investigated in Nigeria. Millet and sorghum grain yield as well as stem borer infestation were not significantly influenced by rate and time of nitrogen application. Borer (Acigona ignefusalis) infestation on millet was very severe in 1984, resulting in total crop failure. In 1985, millet produced grains because of lower borer infestation and damage; the yield of sole millet was thrice that of millet in mixture, whereas the sole crop density was twice that in the mixture. Unlike millet, sorghum produced grains in 1984 despite severe damage by Busseola fusca. Sole sorghum yielded five times the mixture in 1984 but two and a half times in 1985. Borer damage was generally more severe in the mixture.

A survey of Heliothis spp. and their larval parasitoids was conducted in the states of Andhra Pradesh and Maharashtra, India during the period 1977–1983. H. armigera and H. peltigera were recorded on safflower. H. peltigera was found dominant on sole crop, while both the species were equally important on intercrop. In general, eight parasitoids: four Hymenoptera and four Diptera emerged from the larvae of Heliothis spp. Six parasitoids were recorded from H. armigera larvae on sole crop and eight on intercrop safflower. The level of parasitism in H. armigera was higher on sole crop.

Field plots and cage experiments were conducted to study the effects of intercropping sorghum, millet and maize on infestation by the most important lepidopterous stem-borers of the three crops. Intercropping was done both within and between rows. The highest number of B. fusca eggs were deposited on sorghum, followed by maize and least on millet, among the sole crops. The number of eggs found in the crop mixtures was intermediate between the numbers obtained when the crop components comprising the mixtures were considered as sole crops and averaged. The inability of B. fusca adults to effectively utilize millet for oviposition, reduced larval infestation of sorghum stems when interplanted with millet. The best combination was millet interplanted with sorghum in alternate stands within the same row. The millet stem-borer, A. ignefusalis also showed definite preference for millet, but infestation on millet did not seem to be affected by intercropping with either sorghum or maize.