Scientists hope hungry weevils from Louisiana can tackle South Africa's invasive water plants

HARTBEESPOORT, South Africa (AP) — Dozens of tiny black weevils cling onto a fern plant as it is tossed onto a leafy green mat coating the surface of South Africa's Crocodile River.

Those weevils aren't tossed into the river by accident: scientists hope that the insects and their larvae will munch their way through the green mat, which is made up of an unwanted, invasive South American aquatic plant called Salvinia minima.

The plant is steadily taking over freshwater bodies in the northern region of South Africa, suffocating aquatic life, including on the Crocodile River and the Hartbeespoort Dam it flows into.

The weevils, which have been used effectively elsewhere in the world to fight water weeds, are now leading South Africa’s charge against the life-sucking plants threatening ecosystems in at least three northern provinces and creeping into neighboring countries.

After the weevils helped control the spread of salvinia in parts of the United States, scientists from both countries worked together on a project to gather a starter population in South Africa.

The 1-millimeter-long (0.03 inches) insects were brought over 8,700 miles from Louisiana. Rearing stations are being set up near several dams to grow the weevil population.

Once released at an infested site, the beetles make themselves at home on the salvinia, the only thing they eat, without damaging the local ecosystem, scientists say.

“They lay eggs on this plant, feed on this plant and die on this plant. If this plant dies, they will die as well,” said professor Julie Coetzee, the principal scientist at the South African Institute for Aquatic Biodiversity. “They damage certain tissues, those tissues become waterlogged and then those plants sink to the bottom.”

Hartbeespoort Dam north of Johannesburg, the location for the pilot project, is an important source of irrigation for nearby farms and a popular recreation site.

“When we bought the property there was this beautiful little floating plant on the dam and I thought well that’s quite nice,” said 53-year-old resident and business operator Max Moller. “Little did I realize this little floating fern was an absolute menace.”

Moller, the owner of Mogi’s hiking trail, said the salvinia have clogged up and damaged boat engines and also hurt fishing communities over the nine years that he has lived in the area.

South Africa’s already vulnerable freshwater systems face a significant threat from salvinia, scientists say. The plants have had two major growth spurts in 2021 and 2022, surviving on the high nitrate contents in the water.

The plant initially surfaced more than a decade ago at the dam, which has also long been battling with a water hyacinth invasion, another problematic species.

“If you pull the hyacinth away, this plant is lurking,” said Coetzee. The invasive plants block out the sunlight, which means no oxygen in the water, she said.

"If there is no oxygen, there’s no fish, there’s no crab, there’s no insects and so you completely destroy or alter the aquatic ecosystem,” she said.

Salvinia has a rapid growth rate and its spread has been most notable across Gauteng province, where South Africa's biggest city of Johannesburg and its capital, Pretoria, are located. The plant is compounding existing water supply problems by depleting the oxygen and sapping the supply in a country that's already struggling with increasing demand and deteriorating water infrastructure.

While releasing the weevils will help combat salvinia, experts warn that there could be unintended side-effects.

Anthony Turton, a water expert and researcher at South Africa’s University of the Free State, cautioned that their introduction could turn rivers and dams into more suitable homes for bacteria and dangerous organisms.

That includes poisonous blue-green algae, known as cyanobacteria, which flourish in nutrient-rich, contaminated waterways and already affect almost 60% of the nation’s dams.

“With more light and less competition for nutrients, those cyanobacteria will go into a condition known as a bloom,” he said. “This is exponential population growth that radically populates the entire water column.”

Turnton said simultaneous action to repair damaged sewage systems and limit agriculture fertilizer runoff are essential for a lasting solution.

“Unless there are efforts to reduce the inflow of nutrients from sewage flows, then we are only creating space for cyanobacteria to grow without competition from floating weeds,” he said.

The weevils aren't the first insects to be introduced to curb an invasive threat in South Africa. The country brought in a bug in the 1930s to control the spread of a hardy cactus native to Mexico that was hurting ecosystems. That project was viewed as a success.

The speedy growth of the salvinia has put pressure on the government to act, particularly as researchers warn that neighboring countries also now face an invasion.

Coetzee said that salvinia was popping up on the confluence of the Crocodile and Limpopo rivers in the far north of South Africa.

“That now poses a huge threat to our neighbors because this plant has been transported by our rivers onto our borders,” she said. “It is likely to go all the way along the Limpopo, along Botswana and Zimbabwe’s borders and into Mozambique.”

“We really have a responsibility to control this plant," she added.

AP Africa news: https://apnews.com/hub/africa

Hyacinth grows at the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

Hyacinth grows at the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

A community member fishing along the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

Community members fish along the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

A carpet of Salvinia minima ferns grows at the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

Dozens of tiny black weevils cling onto Salvinia minima ferns held in a container at the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

Deputy Minister of Water and Sanitation Isaac Sello Seitlholo tosses out samples of Salvinia minima ferns infected with black weevils onto a carpet of the ferns growing at the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

Hyacinth plants grow at the Hartbeespoort Dam in South Africa, on March 17, 2025. (AP Photo/Themba Hadebe)

Community members fish along the Hartbeespoort Dam in South Africa, on March 17, 2025, near Hyacinth plants in the water. (AP Photo/Themba Hadebe)

DEIR AL BALAH, Gaza (AP) — Israeli strikes killed more than a dozen people in the Gaza Strip early Friday, as Israel sent more ground troops into the Palestinian territory to ramp up its offensive against Hamas.

At least 17 people, some from the same family, were killed after an airstrike hit the southern city of Khan Younis, according to hospital staff. Hours later, people were still searching through the rubble, looking for survivors.

The attack follows days of Israeli strikes, which have killed at least 100 people, as it intensifies operations, intended to pressure Hamas to release its hostages. On Friday, Israel said it had begun ground activity in northern Gaza, in order to expand its security zone.

Israel’s military had issued sweeping evacuation orders for parts of northern Gaza before expected ground operations. The U.N. humanitarian office said around 280,000 Palestinians have been displaced since Israel ended the ceasefire with Hamas last month.

In recent days, Israel's vowed to seize large parts of the Palestinian territory and establish a new security corridor across it.

To pressure Hamas, Israel has imposed a monthlong blockade on food, fuel and humanitarian aid that has left civilians facing acute shortages as supplies dwindle — a tactic that rights groups say is a war crime. Israel said earlier this week that enough food had entered Gaza during a six-week truce to sustain the territory’s roughly 2 million Palestinians for a long time.

Hamas says it will only release the remaining 59 hostages — 24 of whom are believed to be alive — in exchange for the release of more Palestinian prisoners, a lasting ceasefire and an Israeli pullout from Gaza. The group has rejected demands that it lay down its arms or leave the territory.

The predawn strike on Friday hit a three-story building. In addition to the dead, the attack wounded at least 16 people from the same family. Associated Press reporters saw bodies being carried out in blankets, while others searched for people trapped under the rubble and collected charred remains.

“We don’t know how to collect them and how to bury them. We don’t know whose remains these are. They were burned and dismembered,” said Ismail Al-Aqqad, whose brother died in the strike, as well as his brother’s family.

On Thursday, more than 30 bodies, including women and children, were taken to hospitals in and around Khan Younis, according to hospital staff.

Israel said Friday that it had killed a top Hamas commander in a strike in Lebanon’s coastal city of Sidon. Israel said that Hassan Farhat was a commander of Hamas’ western area in Lebanon and that he was responsible for numerous attacks against Israel, including one in February 2024, which killed an Israeli soldier and injured others.

The war began when Hamas-led militants attacked southern Israel on Oct. 7, 2023, killing around 1,200 people, mostly civilians, and taking 251 hostages, most of whom have since been released in ceasefire agreements and other deals. Israel rescued eight living hostages and has recovered dozens of bodies.

More than 50,000 Palestinians have been killed in Gaza as part of Israel's offensive, according to Gaza’s Health Ministry, which doesn’t say whether those killed are civilians or combatants. The ministry says more than half of those killed were women and children. Israel says it has killed around 20,000 militants, without providing evidence.

The war has left most of Gaza in ruins, and at its height displaced around 90% of the population.

Follow AP’s war coverage at https://apnews.com/hub/israel-hamas-war

Palestinians grieve over the bodies of their relatives, who were killed in an Israeli airstrike, at the Baptist Hospital in Gaza City, on Thursday, April 3, 2025. (AP Photo/Jehad Alshrafi)

Relatives mourn the body of Ashraf Al Aqqad, who was killed in an Israeli army strike, before his burial at the hospital in Khan Younis, southern Gaza Strip, Thursday, April 3, 2025. (AP Photo/Abdel Kareem Hana)

Mourners pray over the body of a woman killed in an Israeli army strike, before her burial at the hospital in Khan Younis, southern Gaza Strip, Thursday, April 3, 2025. (AP Photo/Abdel Kareem Hana)

Palestinians who were injured in an Israeli airstrike, are brought for a treatment at the Baptist Hospital in Gaza City, on Thursday, April 3, 2025. (AP Photo/Jehad Alshrafi)

A young Palestinian girl who was injured in an Israeli airstrike, is brought for a treatment at the Baptist Hospital in Gaza City, on Thursday, April 3, 2025. (AP Photo/Jehad Alshrafi)

Smoke rises after an explosion in the Gaza Strip as seen from southern Israel, Friday, April 4, 2025. (AP Photo/Leo Correa)

Yamama Jundia, 13, injured in an Israeli airstrike, grieves alongside others over the bodies of their relatives, who were killed in the same strike, at the Baptist Hospital in Gaza City on Thursday, April 3, 2025. (AP Photo/Jehad Alshrafi)