| An effective protection of sugar beet crop is best achieved through an integrated approach that combines mechanical barriers, biological methods, and appropriate seed selection. Single measures are not sufficient. What matters is a well-coordinated interplay at the right time, because the sugar beet weevil (Asproparthenis punctiventris) often occurs in mass outbreaks but only for a short period, and predictions are uncertain.
Before field establishment, the infestation risk must be carefully assessed. Relevant factors include the previous year´s situation on neighboring fields, the location of the field relative to previous cultivation sites, as well as natural barriers and potential feeding sites.
When establishing the field, extended planting furrows with pheromone traps are central to defense and monitoring. On sides with a high probability of immigration, sufficiently dimensioned trenches should be created early. Pitfall buckets placed at regular intervals ensure targeted capture of the beetles. Once immigration begins, treatments should be initiated in the trench area and captured beetles removed regularly. The maintenance and monitoring effort is considerable, but it largely determines crop stand preservation.
The ASPROSOLUTION project investigated the use of the genus Metarhizium spp. Both the BIPESCO 5 strain and indigenous strains from beet fields can infect and kill the sugar beet weevil. An immediate acute effect is not to be expected due to the mode of action. Multiple spray applications increase infection probability and gradually reduce population density.
Studies on the gut microbiome show that Metarhizium was predominantly re-isolated from infected beetles. High bacterial diversity also protects the sugar beet weevil from pathogens. In the future, targeted manipulation of the microbiome could further increase the efficacy of Metarhizium. Careful risk assessment, consistent seed selection, proper setup and maintenance of pitfall trenches with pheromone traps, regular removal of captured beetles, and – if approved — repeated Metarhizium applications together provide a practical, robust protection that effectively limits feeding damage. |