“Pesta” and alginate delivery systems of Fusarium spp. for biological control of Striga hermonthica (Del.) Benth. under Sudanese field conditions

The parasitic weed, Striga hermonthica, is one of the main biotic factors affecting cereal production in the semi-arid tropics. Field experiments were conducted at Gezira, Sudan, in two consecutive seasons (2003/2004), to study the efficacy of two Fusarium isolates originating from Sudan (Fusarium nygamai (FN) and Fusarium sp.“Abuharaz” (FA)) formulated in wheat flour-kaolin granules on Striga infestation and to determine the dose needed for effective weed control. Furthermore, an alginate formulation was tested as alternative delivery system. In the first season the highest control efficacy was achieved by applying FA in “Pesta” granules at 1.5 g per planting hole, which reduced the total number of parasite shoots by 82% and the number of healthy Striga shoots by 88% compared to the untreated control. As a consequence, sorghum biomass and sorghum 100-seed weight were increased by 88% and 110%, respectively, compared to the untreated control. FN and the combination of the fungal isolates were slightly less efficient in controlling the parasites. During the second season all preparations applied at 1.5 g per planting hole showed a lower efficacy in reducing Striga total number compared to the first season. Nevertheless, FA formulated in “Pesta” or alginate pellets caused disease in 74% and 80% of the Striga plants, respectively, and consequently improved sorghum performance.