Situation regarding important insect pests in oilseed rape in the Czech Republic after four years without neonicotinoid insecticidal seed treatments

Abstract: Central Institute for Supervising and Testing in Agriculture (ÚKZÚZ), as an independent Czech state institution, provide information on the large-scale field monitoring. Of the proportion of land sown to oilseed rape is almost 16% of arable land in the Czech Republic. Higher proportions of oilseed rape in the crop rotation bring problems with increased pests and disease incidence in the crops. Problems with insect pests became noticeably worse after the ban on neonicotinoid seed treatments. Among the most important insect pests of Czech oilseed rape are Ceuthorhynchus pallidactylus, C. napi, Brassicogethes aeneus, and Dasineura brassicae with C. obstrictus (syn. assimilis). Autumn pests became more important a few years before the neonicotinoids ban, especially in the case of Psylliodes chrysocephala (= chrysocephalus) and generally-occurring Phyllotreta spp. After the ban, the pest problems grew. Two years ago, problems with minor pests, e. g. aphids (Brevicoryne brassicae, Myzus persicae), and Plutella xylostella started. In the recent years, the outcomes of state monitoring confirm strong occurrences of oilseed rape pests and consequently severe damages in the crops. The reason for the increasing severity in ‘minority pests’ is not only the changing climate but also the high proportion of oilseed rape in the crop rotation and onset of resistance in intensively-treated crops. The reason for numerous autumn spray applications is the prohibition of seed treatments. The price of oilseed rape is currently stagnating and therefore it is necessary to think about the economy of the crop, which is unprofitable due to the prohibition of seed treatments.