Biological control of Striga hermonthica by Cubitermes termite mound powder amendment in sorghum culture

Striga hermonthica (Del.) Benth is an obligate root hemi-parasite of several cereals. Its effect on cereal crops is the main constraint for food production in sub-Saharan Africa. Various control methods have been already proposed, but the infestation by these parasitic plants persists. An appropriated method for Striga management adapted for the African farmer is very much needed. In this study, amendment of soil infested by this phytoparasite with Cubitermes mound powder is proposed as chemical amendment and natural microbial inoculum, to promote plant growth and reduce damage by S. hermonthica on sorghum (Sorghum bicolor L.). The influence of Cubitermes mound powder on the development of several microbial groups (arbuscular mycorrhizal fungi, actinomycetes, saprophytic fungi) was investigated in a pot experiment with sorghum cultured in a sandy soil infested by S. hermonthica. In the amended soil, sorghum growth and mycorrhizal colonization of sorghum plants were significantly greater than in the control treatment. Mycorrhizal colonization was negatively correlated with the number of emerged Striga plants per pot and positively correlated with sorghum growth. The relationship with substrate-induced respiration (SIR) responses showed that amended soil was characterized by its response to hydroxybutyric acid (catabolic marker of mycorrhizal colonization) and non-amended soil by its response to phenylalanine. We noted that the number of emerged Striga plants in amended pots was significantly decreased. Since Cubitermes mound suspensions did not affect Striga seed germination under axenic conditions, it suggests that the amendment with Cubitermes powder reduces S. hermonthica infestation indirectly, i.e. via its effect on the indigenous soil microflora. Overall, it appears that management of Cubitermes mounds is a promising strategy to consider for effective protection of sorghum from Striga infestation. (c) 2007 Elsevier B.V. All rights reserved.