Temporal dynamics of pesticide use in three field vegetable crops with respect to sowing date and degree days

We analysed the timing of pesticide treatments for eventual analysis of temporal environmental risks associated with pesticide use in field vegetable crops. At the same time, we investigated whether farmers followed the Integrated Pest Management (IPM) instructions. The data cover chemical plant protection in field vegetable farms in southwestern Finland in 2009–2019. The timing of treatments, made with different pesticides in the weeks following sowing, corresponded with the known phenology of different pests of carrot, swede and fresh pea. The same was true for the carrot fly, the pea moth and the second generation of the cabbage root fly when phenological flight time models using historical data were used to predict the timing of treatments. We conclude that farmers acted in accordance with the principles of IPM when practising chemical control. For those species that lacked phenological predictive models in the study years, the degree days for the observed timing of treatments can be used as a starting point if such models are developed in the future. Our results can be used as a long-term baseline in future surveys on the changes in pesticide use and their risks regarding the studied crops.