Striga species distribution and infestation in cereal food crops of northern Côte d’Ivoire

Abstract

Most cereal food crops in Côte d'Ivoire are infested by Striga species. In this study the distribution, abundance and degree of infestation of Striga species were determined. Infested areas under cereal crops were estimated. Data was collected through extensive and intensive surveys and field visits. According to the updated map of Striga infestation, infested areas covered all the north of the country between latitudes 8°47.17' N to 10°38.84' N and longitudes 2°47.68' W to 7°55.20' W. The infested zone covered 3,191,850 hectares of farmland. 71.8% of the villages located in the region were infested by Striga species. The hypothesis of an extension of Striga infestations according to a north-south gradient was confirmed. Infestations began in the Sudan Savannah zone and have now reached half of the sub-Sudanian Savannah zone. Striga hermonthica, with a frequency of 97.1%, was the most abundant species under cereal crops, followed by Striga aspera (2.0%) and Striga asiatica (0.9%). Striga gesnerioides was not recorded on cowpea. Mutants of S. hermonthica and S. aspera with white flowers were identified. Red-flowered morphotypes of S. asiatica were found parasitizing upland rice. S. hermonthica is a major threat to cereal crop production in northern Côte d'Ivoire where it severely infested 57.2% (268,250 ha) of lands under maize (108,160 ha), millet (38,300 ha), sorghum (30,360 ha) and upland rice (91,430 ha). The infestation rates under millet, maize, sorghum and upland rice were 65.9%, 56.5%, 51.0% and 40.5%, respectively. Striga has today become a major national threat to the production of these cereals as well as to food security in endemic areas.