This archive report was first published on 29 August 2019.
Striga, a parasitic weed, has been devastating rural households in western Kenya for years. The weed's prolific seeds can remain viable in the soil for over 20 years, causing significant yield losses of 20-100 per cent in maize.
However, a new technology offers hope to farmers affected by striga. Imazapyr-resistant (IR) maize technology has two components: herbicide-resistant maize seed and a herbicide coating that kills sprouting striga seedlings.
As the maize seeds germinate, they take in the herbicide, which induces germination of the striga weed. However, as the striga seedlings attach themselves to the roots of the maize to draw nutrients, they are killed by the herbicide.
For effective control, farmers need to combine this technology with good agronomic practices such as planting crops in alternating sequence or leaving infested fields. Rotation with non-host crops further breaks the addition of striga seed into the soil and improves soil fertility.
Heavy infestation of striga is an indication of soil deficient of minerals salts, especially nitrogen and phosphorous. Addition of nitrogenous fertiliser, especially from ammonium source, leads to significant reduction in striga numbers.
Intercropping IR maize with legumes is also a viable option. Legume crops improve the fertility of the soil and cover the soil, helping to smother weeds. However, care should be taken while handling the legume seed after planting IR maize, as the herbicide is detrimental to legume seeds.
Two IR maize seeds, H528-IR and FRC425-IR, have been developed to overcome striga. They retail from Sh360 to Sh500 per 2kg packet and are available in agro shops in striga-prone areas.
When planting IR seed varieties, farmers should use gloves while handling the seed and avoid planting IR seed in the same hole with other seeds for those intercropping. Washing hands before handling other seeds is also essential.
