Strategies to stop Striga
Strike One: Prevention is better than cure

In an integrated Striga management programme in Nigeria by the International Institute of Tropical Agriculture (IITA), one important part of the strategy is to reduce Striga damage by limiting dispersal of seed, which can get transferred by livestock hooves, through transport of dung, and by planting crops contaminated with Striga seeds. However, this is easier said than done as each Striga plant can produce anything up to half a million seeds. Each one is virtually microscopic and can remain viable in the soil for up to 14 years. IITA stress that use of parasite-free planting material is essential combined with crop rotation and nitrogen-fixing cultivars, which help to improve soil fertility as well as reduce the density of Striga. Soybean, for instance, produces enough root exudant, the stimulant required to make Striga germinate, but is a non-host crop which stops the parasite from developing.

credit: Dr Charlie Riches, NRI

Sunnhemp, or Crotalaria Spp+ is another leguminous crop, which can be grown as a green manure crop and used as an alternative to fertiliser. Working with farmers and alongside Tanzanian scientists from Ilonga Agricultural Research Institute and Sokoine University of Agriculture, a collaborative project funded by the DFID Crop Protection Programme has tested the use of the green manure in trials in the south of Tanzania on the shores of Lake Nyasa. The results have shown that upland rice farmers, who have grown Crotalaria for a year, have managed to get much improved yields - equivalent to using 30 to 40 kg of urea per hectare - which has proved too expensive for farmers to use. The results have been especially encouraging, as rice yields in the region have plummeted over the past 20 to 30 years from 15 to as little as two bags per hectare. And, like soybean, Crotalaria helps to reduce the Striga seed bank in the soil.

+ Crotalaria juncea and Crotalaria ochroleuca (also known as Marejea in Kiswahili)