A fungus to the rescue

Striga weed: beautiful but dangerous

Striga weed: beautiful but dangerous

Whenever the name fungus – or its plural fungi – is mentioned, the first image that comes to the mind of an agriculturist or anyone with the knowledge of plant pathology is that of a disease-causing microorganism. So, to many, it may be surprising to hear that a fungus can also be used to fight crop weeds and thus be beneficial to agriculture.

Recently, researchers in Kenya concluded successful field trials on the use of a variant of the Fusarium oxysporum fungus to fight Striga weeds (also known as witch weed) on maize fields by coating the maize seeds with the fungus before planting. The fungus attacks the striga weed underground, where it causes most of the damage done to the host crop, before emerging from the soil.

Striga spp, a group of parasitic weeds that infest crops, especially major food crops like maize, rice, sorghum and legumes, are obligate weeds that depend on a host for germination. A Striga weed colonizes the root of a crop underground, drawing moisture and nutrients from the crop, until it emerges from the soil after 4 – 7 weeks later. By then, the main damage has been done and symptoms on crop often resemble that of drought or nutrient deficiency e.g. chlorosis.

Hence, the yield loss caused as result of striga infestation is often substantial and can range from 40 – 100%. Besides, it is believed that up to 40% of Africa’s arable savanna area is infested by striga weeds with a resultant economic loss of up to $13 billion annually.

Also, striga infestation indirectly promotes bush burning, forest degradation and land clearing for agricultural purposes as most of the affected farmers in Africa are smallholders who cannot afford the cost of herbicidal control – which could be ineffective – and are therefore forced to abandon their lands and seek new farming lands.

Consequently, this new bio-control method – which will be produced by the Kenyan company Real IPM, in a project headed by IITA and icipe – will not only help improve grain yields and food security in Africa – while increasing farmers’ incomes – but will also help prevent increased use of synthetic herbicides and reduce other unintended consequences of agriculture such as bush burning, land clearing and forest degradation that contribute to climate change.

First published on Ecoagriculturist Blog

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