Between 1969 and 1972, US released a weevil to fight musk thistle; it later attacked native thistles

Rhinocyllus conicus (Image Credit: Canva) A biological control programme launched in the United States more than five decades ago has become a cautionary example of how attempts to manage invasive species can produce unexpected ecological consequences. According to a USDA Forest Service assessment of invasive species in the Southwest, the thistle seedhead weevil (Rhinocyllus conicus) was introduced to the US between 1969 and 1972 to help control musk thistle and other invasive thistles. The insect was expected to weaken the plants by attacking their reproductive structures and reducing seed production. However, after becoming established and spreading beyond its original release areas, the weevil also began feeding on native thistles. Its impact eventually extended to numerous native species, including endangered native thistles. The case highlights the difficulty of ensuring that a biological control organism remains focused on its intended target once it has been released into a complex natural ecosystem.Why musk thistle was targetedMusk thistle (Carduus nutans) is a non-native flowering plant belonging to the sunflower family. It can become a serious weed in rangelands, roadside...