EFFECT OF HERBICIDE AND HANDWEEDING ON CURRENT AND SUBSEQUENT SEASON STRIGA-HERMONTHICA DENSITY ON SORGHUM

Striga hermonthica is an important cause of yield loss in sorghum in t he semi-arid zone of Africa. Two trials were conducted in northern Cam eroon to evaluate the effect of herbicides for two cropping seasons on densities of emerged Striga in treatment years and on densities of St riga seed and plants in subsequent years. Herbicide application using 2,4-D, triclopyr, paraquat, and bromoxynil and urea solution (20%) was compared with hand-weeding of Striga and an unweeded control. Reducti on of emerged Striga density was greatest with 2,4-D and triclopyr. So rghum grain yield was greatest in the urea solution treatment. Subsequ ent (third-year) Striga seed densities were not significantly differen t, although they were substantially lower in the 2,4-D-treated plots. Emerged Striga densities in subsequent years were generally not signif icantly affected by previous herbicide treatments. One major source of variation in Striga density in the first year following the Striga su ppression treatments was plot position along the slope, reinforcing th e hypothesis that soil moisture plays a major role in Striga germinati on.