DYNAMICS OF FLOWERING AND EMBRYOLOGY OF STRIGA-HERMONTHICA (DEL.) BENTH. (SCROPHULARIACEAE) - IMPLICATIONS FOR CHEMICAL CONTROL

Striga hermonthica (Scrophulariaceae) is one of the greatest scourges of food crops in semi-arid areas in Africa. To improve the efficiency of a chemical treatment using 2,4-D, the dynamics of flowering togethe r with the embryology of S. hermonthica were studied on untreated and treated plants growing in field conditions. It was established that th e flowering period lasts 21 to 25 days. Embryogenesis, conforming to t he Capsella type, shows a key step, i.e. the hypophysis initiation, oc curring 7 to 10 days after the opening of the flower. Treatments appli ed before this step destroy the embryos whereas later treatments are i neffective. The best results are obtained with two or three low doses of 2,4-D, the first one being applied at the beginning of the flowerin g period and the others at an interval of 10 to 12 days. However, to c onvince smallholders of the effectiveness of the method, an important campaign of information and training is necessary.