adaptive-background

Striga asiatica

Preferred Scientific Name: Striga asiatica

Striga asiatica is a much feared weed in crop land, where infestations can build up to ruinous levels. 

Striga asiatica
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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.

Impacts

  • Parasitizes crops
  • Reduces native biodiversity
  • Negatively impacts livelihoods

What’s the solution? 

Host resistance 

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. 

Chemical control

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. 

Biological control

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. 

Fact file

Name Striga asiatica

Distribution

Asia, Africa, North America, Oceania

For more information on distribution, view the full datasheet available here

Habitat

Cultivated land

Natural enemies

The moth, Eulocastra argentisparsa and the gall-weevil, Smicronyx albovariegatus

Invasiveness

Broad native range, high genetic variability and high reproductive potential

Likelihood of entry

High risk of accidental introduction

Climate

Tropical

Type

Parasitic

Further reading

Visit our online resource of research and full text articles and journals
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