Lupin Root Weevils (Charagmus spp., Curculionidae: Sitonini), a Lupin Pest: A Review of Their Distribution, Biology, and Challenges in Integrated Pest Management

SIMPLE SUMMARY: Lupin root weevils comprise two beetle species that cause major damage to lupin crops. These weevils have spread widely in Europe, but damage specifically occurs in very light sandy soils. The adults feed on the leaves of lupins; however, the larvae feed on the root systems, causing major damage. These larvae develop underground by feeding on the root nodules. Additionally, controlling the adults is challenging because of their cryptic behaviour. Conventional control with insecticides has limited success. Therefore, alternative management practices are needed. In addition to the biology of these pests, we provide an overview of several crop management measures as well as a range of biological control options. These measures could help control lupin pests, thus supporting the cultivation of lupins as a valuable crop rotation element and an important source of protein for food and feed. ABSTRACT: Lupins (Lupinus spp.) are an ancient yet important legume crop. In Europe, the protein-rich seeds serve as livestock feed and have the potential to be a healthy vegetarian component of human diets. In some regions in north-eastern Europe, lupins are heavily damaged by two Curculionidae species, the lupin root weevils (LRWs) Charagmus gressorius (syn. Sitona gressorius) and Ch. griseus (syn. S. griseus). Narrow-leaved lupins (L. angustifolius) and white lupins (L. albus) are most affected. The weevils feed on lupin leaves, whereas their larvae feed on root nodules. Therefore, the larvae cause major root damage by creating lacerations that allow soil-borne plant pathogens to enter the plant tissue. These infestations lead to considerable yield losses and markedly reduced N-fixation of the root nodules. This review summarises the current knowledge on the origin, geographical distribution, and biology of these rarely described weevils. It focuses on management strategies, including preconceived insecticide use and potential ecological management methods, as key components of an integrated pest management programme against LRWs in Europe.