What is Striga?

Striga Asitica on maize
© Jonne Rodenburg

What is Striga?

In Sub-Saharan Africa, we can witness a striking view of numerous vibrant purple and red flowers covering many crop fields. Although it is captivating, those flowers belong to the parasitic plant Striga, also called witchweed. It is a parasitic plant, that infects the root systems of many crops, syphoning water and nutrients and ultimately leading to devastating effects on crop growth and yield. For sorghum, millet, and rice, the estimated annual production losses due to Striga alone amount to more than 6 million tons of grain, worth more than 2 billion USD annually. Combined with the increasing adverse effects of climate change, production of these cereal crops across Sub-Saharan Africa is in jeopardy.

In this project, we will focus in two main species of Striga, Striga hermonthica and Striga asiatica. 

  • Striga hermonthica
    Jos Raaijmakers
    Striga hermonthica
  • Striga asiatica
    Jonne Rodenburg
    Striga asiatica

The Lifecycle

Striga plants can produce a considerable number of seeds (ranging from 90,000 to 500,000 per plant), which are deposited in soil and can remain viable for over 10 years. Once the Striga seeds perceive specific signals present in root exudates from the crop plants, also referred to as strigolactones, germination begins. The germ tube of the Striga seeds grow towards the crop roots and form haustoria, root-like structures that penetrate the crop roots. After penetration of the crop roots, Striga establishes a so-called xylem-xylem connection allowing the parasite to take the water and nutrients from its host.  Throughout this phase, Striga remains subterranean, but within four to seven weeks, it emerges above ground and will start flowering forming a massive amount of seeds to complete its life-cycle.

Image: Xavier Pita, KAUST

Striga Lifecycle

The Impact

Striga hermonthica has been reported in at least 32 countries, and S. asiatica in 42 countries (Rodenburg et al., 2016). Together they infest 12-38% of the area under cereal production in Africa. Striga causes substantial yield losses, often leading to field abandonment and food insecurity for small-scale farmers⁠. For the three crops combined (sorghum, millet, rice), the estimated annual production losses amount to 6,213,000 tons of grain, worth $2,315 million USD annually. Combined with the increasing adverse effects of climate change, production of these cereal crops across the African continent is severely affected. This is particularly evident for resource-poor farming communities in Sub-Saharan Africa that rely heavily on these crops for their livelihood.

Image: Victoria Miles, NIOO-KNAW

Distribution Striga