By Sara Hendery
Where the invasive weed Parthenium hysterophorus once thrived, the release of two host-specific insects—Zygogramma bicolorata and Listronotus setosipennis—is significantly increasing farmer access to fertile lands.
Parthenium is an incredibly destructive weed native to Central and South America that has accidentally been introduced to many regions of the world including Australia, Asia, Africa, and the Pacific Islands. It dramatically reduces crop yields, causes human health issues such as respiratory problems and rashes, and taints valuable livestock milk. Found scouring roadways and invading farmland, Parthenium creates difficult conditions for farmers to grow food.
Beginning in 2005, Virginia Tech’s Feed the Future Innovation Lab for Integrated Pest Management (IPM Innovation Lab) and Virginia State University initiated a classical biocontrol program to manage the weed in East Africa, where the spread of invasive species is especially detrimental to biodiversity and the livelihoods of rural people who rely on natural resources.
Recently, Zygogramma bicolorata—a leaf-feeding beetle—demonstrated consistent establishment in Ethiopia and Uganda, and Listronotus setosipennis—a stem-boring weevil—did so in Ethiopia. Since the two natural enemies of Parthenium were released 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. After defoliating the weed in those locations, the insects have now spread from the initial release sites to adjacent fields.