Western Corn Rootworm

Diabrotica virgifera virgifera — the western corn rootworm — is the most economically destructive insect pest of US corn agriculture and one of the most-cited model organisms in pesticide and biotechnology resistance evolution. The species is native to North America, originally adapted to feeding on the roots of wild teosinte (the Mesoamerican grass ancestor of corn). After corn was domesticated and spread northward in the prehistoric era, western corn rootworm spread with it, and after corn became the dominant US row crop in the 19th-20th centuries, the species exploded in abundance across the US Corn Belt. Larvae are the damaging life stage: small white grubs that feed on corn root systems for 4-6 weeks in early summer, severing root connections and reducing the plant's ability to take up water and nutrients. Heavily infested corn plants often topple in summer storms (the famous 'goose-necking' damage pattern), and yield losses of 15-30% per acre are common in untreated fields. Total US economic impact (yield loss + management costs) exceeds $1 billion per year, earning the species the 'billion-dollar bug' nickname. The species' resistance evolution is a centerpiece case in modern agricultural pest management. Western corn rootworm has evolved field resistance to every major insecticide chemistry developed for control (organochlorines, organophosphates, carbamates, pyrethroids, neonicotinoids) — and, most consequentially, to TWO of the four genetically-engineered Bt corn traits since 2009: Cry3Bb1 (first detected 2009 in Iowa) and Cry34/35Ab1 (first detected 2014 in Minnesota). Bt resistance evolution in this species has reshaped industry approach to genetically-engineered crops, including the use of refuge planting requirements, pyramided multi-Bt traits, and integrated rotation strategies. The species was introduced to Belgrade airport, Yugoslavia in the early 1990s on military and agricultural cargo from the US and has since invaded Hungary, Italy, Croatia, Romania, Bulgaria, France, Switzerland, and other central European countries — making the species one of the most-watched invasive insects in current European agricultural pest surveillance.