Because of the combined efforts of two Virginia land-grant universities, natural vegetation is flourishing anew and farmer access to fertile lands is increasing where a destructive weed once ruled in East Africa.

Invasive in Africa, Asia, and Australia, Parthenium hysterophorus can dramatically reduce crop yields, cause health issues, and taint livestock milk. In developing nations with limited infrastructure and access to technology, the spread of invasive plants is especially detrimental.  

That’s why Virginia Tech’s Feed the Future Innovation Lab for Integrated Pest Management and Virginia State University have collaborated since 2005 to mitigate the spread of parthenium in Ethiopia and Uganda. The teams implement biocontrol, or the release of insects that are natural enemies of the weed, to combat it safely and economically.

Due to challenges in obtaining permits, changing climatic patterns, and identifying release sites with suitable conditions, the success of the natural enemies Zygogramma bicolorata and Listronotus setosipennis had not been that obvious — until recently.

Zygogramma has now consistently “established” in both Ethiopia and Uganda, and Listronotus in Ethiopia. The evidence is replenished farmland where the damaging weed once thrived. 

“‘Establishment’ means that since we released the natural enemies in Ethiopia five years ago, and more recently in Western Uganda, life stages of the insects survived the dry seasons and emerged from the soil in rainy seasons to feed on the weed,” said Wondi Mersie, associate dean and director of research at VSU and lead researcher on the project. “After defoliating the weed in those locations, the insects have now spread from the initial release site to adjacent fields.”

Many areas that were infested with parthenium ⁠— increasing weeding expenses and reducing land value ⁠— are now overgrown with natural vegetation. This replenishment improves conditions for livestock grazing and crop production, both of which are critical for East Africa. In 2019, 18.7 million people across the region were food insecure, an increase of 2 million people since 2018.

“If the growth of parthenium goes unchecked, its spread can easily get out of hand, and we’ve witnessed it happen,” said Muni Muniappan, director of the IPM Innovation Lab. “Its tolerance to drought, high seed production ability, and susceptibility to accidental introduction contributes immensely to its spread, causing economic loss and enabling it to push out native vegetation.”

In just one year, for example, the spread of the weed caused $22 million worth of yield losses in Australia.  

Establishing natural enemies in Uganda is an especially triumphant success, due to obstacles in obtaining permits for their release. Two years ago, the National Agricultural Research Organization in Uganda reached out to the Virginia teams for help. Now, in sites where releases of Zygogramma took place, NARO can see revived land.  

Richard Molo, senior research officer at NARO, said this collaboration with U.S. institutions is helping bring back to life the many losses caused by parthenium.

“In Uganda, occupation of farmlands by parthenium weed has caused low yields of staple food crops, particularly maize and sorghum, leading to food insecurity in households,” Molo said. “The loss of grazing land has forced wild animals to migrate to other areas with enough pastures and this has impacted tourism. … At a national level, this collaboration will improve food security, increase incomes, and increase foreign exchange for the Ugandan government.”

In addition to the scientists from Virginia Tech and VSU, the project has brought together researchers from around the world ⁠— including Ethiopia, South Africa, Australia, and India.

The Feed the Future Innovation Lab for Integrated Pest Management is housed at the Center for International Research, Education, and Development, part of Outreach and International Affairs.

Written by Sara Hendery