Status of Striga species in Tanzania: occurrence, distribution, and on-farm control packages.
Striga species are important as endemic pests of cereals, including sorghum, maize, millets and upland rice, grown in the semi-arid tropical and equatorial regions of Tanzania. The distribution of Striga species of economic importance in the country was extensively surveyed. The most frequently observed species included S. asiatica, S. hermonthica and S. forbesii. Each has been found to have a different geographic range, some of which overlap. Farmers interviewed recognized Striga as a major constraint in cereal production, and they requested an immediate solution to the problem. Preliminary results from on-farm trials have shown that early-sown cereal crops yielded more than late-sown ones, despite higher Striga infestation in early-sown crops. Sorghum or maize intercropped with cowpeas (the spreading type) in the same row resulted in the least Striga emergence, and the highest cereal yield was obtained from this treatment. Sorghum cv. SAR 29, Weijita and Serena showed very low incidence of S. asiatica and S. forbesii compared with the susceptible cv. Tegemeo and Sandala. Cv. Serena was also observed to have the least infestation by S. hermonthica at Ukiriguru. A postemergence herbicide, 2,4-D, applied twice at a rate of 2 kg a.i./ha at 8 and 10 weeks after emergence of sorghum, resulted in low Striga infestation; the greatest sorghum grain yield was also obtained from this treatment.