A survey of Striga spp. (Scrophulariaceae) and their insect natural enemies in East Africa with a discussion on the possibilities of biological control.
The principal species of Striga affecting cultivated plants (especially sorghum, maize, sugar-cane and finger millet [Eleusine coracana]) in East Africa are S. hermontheca and S. asiatica; S. forbesii and S. gesnerioides are also found occasionally. Insects associated with these parasitic weeds were surveyed throughout East Africa, and notes on all the phytophagous species found are given as well as records of their natural enemies. The chief among the phytophagous species were the weevils Smicronyx spp., the stem-mining Agromyzid Ophiomyia strigalis Spencer, the Pterophorid Platyptilia sp. and the Nymphalid Junonia orithya var. madagascariensis Gn. Their importance as controlling factors is discussed and thought to be minimal. The possibilities of biological control of Striga using these, or insects recorded from Striga in India, are examined and, while the prospects are not regarded as promising, it is suggested that the seed-pod galling species of Smicronyx, and O. strigalis, might be introduced into areas where they are not already present and that the Indian moth Eulocastra argentisparsa Hmps. [cf. RAE/A 59, 501, etc.] might prove useful in East Africa. It is concluded that a combination of agronomic methods and biological control will be necessary for the satisfactory control of Striga in peasant agriculture.