Researchers launch Bangladesh’s first biocontrol program to combat invasive weed

A Virginia Tech team has introduced Bangladesh’s first biocontrol program to combat an invasive weed.

Parthenium hysterophorus, a tropical weed native to Central and South America, first reached the South Asian nation in 1988. It can cause up to 50 percent reduction in crop yields, trigger skin and lung irritation in humans, and cause ulcers in the mouths of livestock that consume it. Reported in about 50 of Bangladesh’s 64 districts, the weed spreads rapidly and is a major threat to crop growth.

Virginia Tech’s Integrated Pest Management Activity (IPMA), part of the Center for International Research, Education, and Development and funded by the Bangladesh U.S. Agency for International Development Mission, launched a biocontrol program in Bangladesh that harnesses the use of natural enemies to fight the noxious weed.

Researchers began by releasing Zygogramma bicolorata, a beetle that feeds on the weed’s leaves and causes large-scale defoliation. The insect has been used elsewhere as an effective deterrent to Parthenium growth. For long-term control of Parthenium, IPMA has partnered with Bangladeshi farmers, students, and researchers to plan for continual rearing and release of Zygogramma.

“Biocontrol of Parthenium is an especially important initiative to apply right now to reduce burdens for rural farmers — and the impact will be multipronged,” said Muni Muniappan, director of the IPM Innovation Lab, under which IPMA is an associate award. “Mitigating the spread of this destructive weed will help clear land for animal grazing, increase milk yields, reduce weeding time, and open land for possible crop production without the use of pesticides — which will generally improve human and environmental health.”

In Bangladesh, nearly 40 percent of households face food insecurity. In addition, the use of toxic chemical pesticides in the country has dramatically increased in recent years. Bangladesh is also ranked as the seventh most vulnerable nation to climate disaster, and the threat of invasive species emerging on land essential to crop growth could be dire for its future.

Globally, the spread of invasive species costs economies trillions of dollars annually. Low-income countries, which often greatly depend on natural resources, are disproportionately affected. The IPM Innovation Lab has a long history of supporting developing countries in reducing an invasive species’ threat to the local ecosystems.

In Ethiopia, for example, Parthenium began overtaking vital pasture and cropland in the 1960s. In 2005, the IPM Innovation Lab facilitated Ethiopia’s first biocontrol program for an invasive weed by using natural enemies, including Zygogramma, to fight the spread of Parthenium. This biocontrol program was an important first step in supporting Ethiopia in gaining that land back.

Zygogramma has since been used as a biocontrol agent in other countries and fortuitously spread to Pakistan and Nepal in 2003 and 2009, respectively. Virginia Tech researchers had a hunch that by now the beetle may have reached Bangladesh as well.

In 2022, after scouting for several months, IPMA researchers were the first to discover the beetle in Bangladesh. They trained Bangladeshi scientists, technicians, extension officers, and students on mass rearing and releasing the natural enemy to suppress the weed and also supported the construction of a laboratory and a screen house. After providing training to Bangladesh’s Patuakhali Science and Technology University, IPMA and the institution facilitated the country’s first field release of Zygogramma in an area infested with Parthenium in April 2024.

With training underway in Bangladesh, IPMA aims to involve more institutions in rearing and releasing Zygogramma over the next year. The researchers will conduct an international workshop on Parthenium in Bangladesh to increase visibility and recruit more scientists.

“Mitigating the spread of invasive species is a global effort,” said Guru Ghosh, vice president for outreach and international affairs. “Virginia Tech teams have long invested in other countries in an effort to share knowledge and resources in the fight against invasive species — ultimately protecting native ecosystems, food security, and livelihoods. In the spirit of Virginia Tech’s motto, Ut Prosim (That I May Serve), we know that working together benefits all of us.”