BACKGROUND AND AIMS: Infection by the hemi-parasitic plant Striga hermonthica causes severe host-plant damage and seed production losses. Increased availability of essential plant nutrients reduces infection. Whether, how and to what extent, it also reduces striga-induced host-plant damage is not well studied.METHODS: Effects of improved macro- and micronutrient supply on host-plant performance under striga-free and infected conditions were investigated in greenhouse pot assays. One striga-sensitive and two striga-tolerant genotypes were compared. Plants growing in impoverished soils were supplied with (1) 25% of optimal macro- and micronutrients quantities, (2) 25% macro- and 100% micronutrients, (3) 100% macro- and 25% micronutrients, or (4) 100% of macro- and micronutrients.KEY RESULTS: Photosynthesis rates of striga-infected plants of the sensitive genotype increased with improved nutrition (12.2 to 22.1 µmol/m2/s1) but remained below striga-free levels (34.9-38.8 µmol/m2/s1). For the tolerant genotypes, increased macro-nutrient supply offset striga-induced photosynthesis losses. Striga-induced relative grain losses of 100% for the sensitive genotype were reduced to 74% by increased macronutrients. Grain losses of 80% in tolerant Ochuti, incurred at low nutrient supply, were reduced to 5% by improved nutrient supply.CONCLUSIONS: Increasing macro-nutrient supply reduces striga impact on host-plants but can only restore losses when applied to genotypes with a tolerant background.