Competition in populations of the hemi-parasitic plant Striga hermonthica on a sorghum host

Abstract

Striga hermonthica is a hemi-parasitic plant species that parasitizes species belonging to the Gramineae, including crop species such as maize, sorghum, millet and rice. Competition to increasing density is likely to occur, but has never been fully studied. Individual sorghum plants were exposed to different densities of viable S. hermonthica seeds in a greenhouse experiment. Parasite performance was evaluated at crop harvest and related to the initial seed density, using model selection to determine the shape of the relationship. We found strong intraspecific competition in populations of S. hermonthica, which was most intense during the holoparasitic phase. Despite competition, a continuous and unrelenting effort will be required to keep S. hermonthica seed bank densities below damaging levels.

Keywords

• competition
• hemiparasitic
• holoparasitic