Landscape-scale drivers of insect pest regulation in sugar beet

Recent policy shifts sparked by environmental and health concerns, insecticide resistance development, and limited new registrations have caused a dwindling availability of chemical insecticides. Sugar beet, a major cash crop in temperate agricultural systems, relied on now banned neonicotinoid insecticide seed coatings for pest control, creating a need for sustainable alternatives. Using a monitoring dataset from 134 sugar beet fields in Denmark and Sweden collected over five years, we assessed landscape-scale drivers of the occurrence and damage of five dominant sugar beet pests in the region: black bean aphid, flea beetles, beet leafminers, pygmy mangold beetle and thrips. We found that insect pests generally cause limited damage to sugar beet in our study area, with damage thresholds for any of the five pests being exceeded in 20 % of the fields. Damage by thrips was more common in Denmark and damage by flea beetles and beet leafminer eggs were more common in Sweden. Pest occurrence or damage could only partly be explained by landscape-scale factors. Cropland cover was positively related to black bean aphid and thrips damage presence but negatively related to flea beetle and pygmy mangold beetle damage. Edge density was negatively related to black bean aphid occurrence but positively related to flea beetle damage. An inter-annual increase in host crop cover was positively related to flea beetle damage and crop diversity to beet leafminer infestation. We conclude that further research on the cause and countermeasures for insect pest outbreaks is needed to develop economically and environmentally sustainable insect pest regulation in sugar beet.