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Summary Striga hermonthica is a major biotic constraint to sorghum production in Nigeria, sometimes causing total yield loss. Recommendations for Striga management often include the use of cultural and agronomic practices, herbicides and host plant resistance when available. The use of biological control has not been commercialized. Fusarium oxysporum (isolate PSM 197)‐based mycoherbicide was used in combination with selected sorghums (the Striga‐resistant cultivar Samsorg 40, and the Striga tolerant landrace Yar'ruruka) as an Integrated Striga Management strategy (ISM) in on‐farm trials in the Sudano‐Sahelian savanna of Nigeria. Crop stands were significantly (P = 0.05) higher in ISM compared with non‐ISM plots on which the mycoherbicide was not applied. Similarly, ISM plots had significantly (P = 0.05) lower Striga counts than non‐ISM plots. Striga emergence was reduced by ISM by around 95%. Sorghum yields were 49.6% higher where integrated management was used. Cost benefit analysis of the ISM package shows that use of the mycoherbicide increased the profitability of sorghum production on Striga‐infested soils. Farmers’ preferences monitored during and after the trials highlighted the need for careful selection and integration of control components into an ISM package.

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Striga hermonthica is a major threat to cereal production in Nigeria. Management approaches for control of Striga are generally based on cultural control strategies and host plant resistance. The use of plant products for the control of S. hermonthica is limited. Seed and leaf powders of neem and fruit and fruit peel powders of parkia trees were evaluated under screenhouse and field conditions in the Nigerian Savanna. Screenhouse evaluation of the plant materials showed that neem seed powder was the most effective, with only 16.5% of Striga emergence. This was followed by parkia fruit powder and parkia fruit peel powder, with 29.1% and 38.8% Striga emergence respectively. In the field, all plant materials significantly reduced Striga emergence. The lowest number of emerged Striga plants was observed on plots treated with neem seed powder (with 1.7 emerged Striga per 3m 2 while the control plots had 30.3 emerged Striga plants per 3m 2 ). Crop plants treated with neem seed powder did not show any reaction to Striga infestation, while parkia fruit powder and parkia fruit peel powder had reaction scores of 1.7 and 2.0 respectively when compared to neem leaf powder with 3.0 and the control with 4.7. Treatment by all the plant products however, significantly increased grain yield, which was highest in the treatment with neem seed powder. Our results highlight the possibilities of using these plant products for the control of S. hermonthica.

Fourteen elite sorghum lines were evaluated for their resistance to Striga hermonthica at three locations in Nigeria and Mali. Results showed that many of the lines especially MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64 (Keninke´die´) and the check SRN 39 remained resistant to Striga in all locations with low emerged Striga counts, while SAMSORG 14 had the highest Striga infestation in all locations. Considerable variation in reaction to Striga infestation was observed on Se´gue`tana, 97-SB-F5DT-63 (Wasa), 97-SB-F5DT-65, CMDT 38, CMDT 39 and CMDT 45 which were susceptible to Striga at Samaru, Nigeria but were resistant to Striga at both locations in Mali. Based on low Striga resistance and high grain yield, lines MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64, 97-SB-F5DT-65, CMDT 39 and SAMSORT 14 have been nominated for wider evaluation across more West African countries.

Fusarium oxysporum (isolate PSM 197) based mycoherbicide was evaluated for its efficacy under field conditions in trials conducted during 1999-2001 cropping seasons in the Nigerian savanna. In the 1999 cropping season, spot application of 5-10 g of mycoherbicide was found to give effective control of Striga hermonthica. Results of on-farm trials at Barhim and Dutsen-Ma areas showed the application of the mycoherbicide to significantly (p ¼ 0.05) increase stand count at both 3 weeks and at harvest, reduced Striga shoot count and increased crop yield in both improved and local sorghum varieties, as compared with the same varieties not treated with the mycoherbicide. Results establish the efficacy of F. oxysporum as a mycoherbicide and the need for further development of the mycoherbicide into formulated granules or seed treatment for use in control of S. hermonthica under field conditions.