Removing This Invasive Shrub's Flowers Could Help Combat Malaria


The Prosopis juliflora shrub, an invasive species in Africa, is a type of mesquite. Forest and Kim Starr/Flickr/CC BY 2.0
The Prosopis juliflora shrub, an invasive species in Africa, is a type of mesquite. Forest and Kim Starr/Flickr/CC BY 2.0

Swat a mosquito? You've just conquered one of humankind's greatest enemies, as mosquitoes may be the deadliest animal in the world. Each year, they kill more than 1 million people by transmitting the parasites that cause malaria, a disease that destroys red blood cells and, if untreated, can lead to systemic organ failure.

The solution, however, may be as close as a common shrub. Researchers have discovered that removing the flowers of an invasive shrub from mosquito-rich areas makes significant headway in reducing malaria numbers. A new study published in the Malaria Journal reports that malaria-carrying mosquito populations plummeted by as much as 60 percent in areas using this flower-removal method.

Mosquitoes feed on the flowers of the Prosopis juliflora, and a new study shows that targeted pruning could have an impact on the spread of malaria.
Mosquitoes feed on the flowers of the Prosopis juliflora, and a new study shows that targeted pruning could have an impact on the spread of malaria.
Muller et al., Malaria Journal, 2017

Mali, a country of nearly 15 million people in West Africa, is the site of this first effort to control mosquitoes through environmental manipulation. The targeted shrub, Prosopis juliflora, is a type of mesquite plant native to Central and South America and the Caribbean, but was introduced to Africa to aid in deforestation recovery. The shrub now takes up millions of acres on the African continent — and its flowers have become a favorite of mosquitoes.

To determine the effect of the shrub on mosquito populations, researchers traveled to the Bandiagra District in Mali, where they cut flowering branches off P. juliflora in three of six mosquito-infested villages. In the villages where the flowers were removed, mosquito numbers (as evidenced by mosquito traps) dropped by about 60 percent when compared to mosquito populations in villages where the flowers remained intact.

"Mosquitos obtain most of their energy needs from plant sugars taken from the nectar of flowers," said Dr. Gunter Muller, the study's lead author, in a press release. "Our results show that removal of this particular shrub reduces total population levels of mosquitoes and reduces the number of older female mosquitoes in the population, which are known to transmit malaria parasites to humans. This suggests that removal of the flowers could be a new way to shift inherently high malaria transmission areas to low transmission areas, making elimination more feasible."

The researchers also believe the P. juliflora flower serves as a cautionary tale for those introducing exotic plants to new areas. Not only could these plants become invasive to local flora and fauna, but they could negatively impact public health — just like the P. juliflora attracts mosquitoes that carry malaria.