Invasive-weed-management
Guides
Cassida rubiginosa
Thistle Tortoise Beetle
Cassida rubiginosa, commonly known as the thistle tortoise beetle, is a leaf beetle in the subfamily Cassidinae native to Europe and Asia that has been introduced to North America, New Zealand, and other regions as a biological control agent for invasive thistles. The beetle derives its common name from the tortoise-like appearance of adults, whose elytra and pronotum form a shield-like covering over the body. Both adults and larvae feed on thistle foliage, with larvae possessing a distinctive defensive structure—a forked caudal appendage used to carry accumulated feces and exuviae as a mobile 'fecal shield' that deters predators. The species has demonstrated effectiveness in reducing thistle biomass and seed production, though its host range extends beyond the primary target to other Cardueae species.
Epiblema strenuana
ragweed borer, stem-galling moth
Epiblema strenuana is a tortricid moth native to North America that has been widely introduced as a biological control agent against invasive Asteraceae weeds. Its larvae form stem galls on host plants, functioning as nutrient sinks that place the plant under metabolic stress. The species has established populations in Australia and China, but was rejected for release in India and South Africa due to non-target risks to the oil-seed crop Guizotia abyssinica. Taxonomic confusion with the closely related E. minutana has complicated host range assessments.