Using natural enemies to control invasive weeds might be backfiring, according to new research from the University of New South Wales (UNSW) in Australia. Instead of weakening the weeds, biological control methods could be encouraging them to cooperate and become even more resilient.
The study, published in Trends in Ecology & Evolution, suggests that introducing herbivores, like insects that feed on invasive plants, may inadvertently boost the weeds’ ability to dominate landscapes. By damaging individual plants, these biocontrol agents might cause the weeds to shift energy from competing with each other to working together.
“I don’t think we’ve been measuring the success of biocontrol agents correctly,” said lead researcher Stephen Bonser from the UNSW School of Biological, Earth & Environmental Sciences. “We’ve focused on how well these agents damage individual plants, but we’ve overlooked how the plant populations behave as a whole.”
The weakened weeds, instead of competing to outgrow each other, may start cooperating, allowing them to spread over even larger areas. “What we think is happening is that the biocontrol agents are turning aggressive invaders into cooperative communities,” Bonser explained. “When they cooperate, they can cover massive areas, even more than before.”
To counteract this unintended effect, Bonser and his team are exploring new strategies. These include reintroducing tall native plants to disrupt the weeds’ cohesion or combining biocontrol with other interventions.
