Why is it a problem?
Striga species are native to Africa but have probably extended their range. According to some reports, they originate from the Nubian hills in Sudan and the Simien Mountains of Ethiopia so would be considered to be introduced and invasive in most of Africa. Striga species cause yield reduction of US$53 million in Kenya per annum alone.
- Parasitizes crops
- Reduces native biodiversity
- Negatively impacts livelihoods
What’s the solution?
A single recessive gene, which can be found in some sorghum plants, can result in the crop showing some resistance to Striga asiatica infestation. While the plant is not completely immune, it is likely to be damaged by the weed, even if Striga asiatica is growing in its proximity.
The development of inbred and hrybrid maize varieties has led to a strain of maize that has shown some tolerance to Striga asiatrica. While the weed continues to grow around the maize plant, the damage inflicted on it by Striga asiatrica is minimal.
Herbicides such a 2,4-D readily kills Striga asiatica, when sprayed on weeds that have already emerged. The main disadvantage of this being that farmers have to wait for Striga asiatica to emerge before they can spray it, meaning that it has usually damaged the host plant before it is treated. Equally, crops will need respraying as more Striga asiatica emerges, which can become expensive.
Other herbicides, such a Dicamba, are sprayed onto crops before the emergence of Striga asiatica. This means that the farmer does not need to keep reapplying the herbicide as more of the weed grows. However, Dicamba is significantly more expensive than post-emergance herbicides like 2,4-D.
Striga asiatica has a variety of natural enemies, including a multitude of moths- such as Eulocastra argentisparsa, and fungi- Sphaerotheca fuliginea. The only natural enemy of Striga asiatice that has been implemented as a biocontrol agent is the gall-weevil (smicronyx albovariegatus), which was introduced to Ethiopia in 1974 and 1978. So far there is no evidence that these organisms ever established.