Abstract

The biological control agent Fusarium oxysporum f.sp. strigae isolate Foxy 2 had shown potential as a biological control in West Africa, however it failed to achieve the same results when used on Kenyan Striga hermonthica. A F. oxysporum isolate FK3 was obtained from infected S. hermonthica in a maize crop in Kenya and tested as a potential control agent of S. hermonthica in Kenya. Two pot trials were conducted where the S. hermonthica seed and varying rates of isolate FK3 (7.5 to 60 × 10⁷ CFUs per pot) were added prior to planting of maize. Numbers of S. hermonthica plants were reduced significantly at the lowest rate of FK3 application when compared to the control from 10.7 to 5.5 per pot in the first trial and 21.3 to 7.9 plants per pot in the second trial. Where a more susceptible variety of maize was used in the second trial evidence of improved maize growth (fresh root mass and stover weight) and yield (weight of grains and whole cob weight) was associated with the reduction in S. hemonthica numbers. More extensive field trials are recommended to fully assess the impact of FK3 on maize yield. The findings support the idea that regional genetic variation in both S. hermonthica and the pathogen F. oxysporum may explain the regional specificity of F. oxysporum isolates as a potential biological control agents.

Key words: Biological control, maize, mycoherbicide, parasitic plants, striga, Fusarium.