This paper presents a three-year study concerning the effectiveness of the OSR seed treatment with the cyantraniliprole active ingredient in controlling the DBM larvae attack in autumn and four-year monitoring of the DBM flight pattern, using pheromone sticky traps. The experiment and the monitoring were conducted at the experimental field from the National Agricultural Research and Development Institute (NARDI) Fundulea in Southeast Romania. For the field assessments, each OSR sampled plant was photographed in macro mode, and then images were downloaded and magnified on the PC screen to determine the DBM larva attack. The traps were placed in the OSR crop from mid-March till December and checked twice weekly. Data from the field assessment revealed a higher pest attack on OSR plants on 11 November 2020, when the DBM larvae attack degree was 16.26% in the untreated variant and 11.24% in the variant with treated seeds. The results evidenced unusually higher activity for the diamondback moths during November 2019, 2020, and 2022; the beginning of December 2020 and 2021; and mid-December 2022. This is the first report from the Romanian scientific literature concerning higher DBM attacks at OSR plants in autumn and high moth activity during November and December.