Effect of immigration time and beetle density on development of the cabbage stem flea beetle, (Psylliodes chrysocephala L.) and damage potential in winter oilseed rape

Abstract In a semi-field net cage experiment set up in three growing seasons (2015–2018) at Julius-Kühn Institute Braunschweig, Germany, the influence of different release times adult cabbage stem flea beetles, Psylliodes chrysocephala (early September, mid-September, early October) and beetle densities (6.7, 13.3 20 beetles/m 2 ) on reproduction damage potential winter oil seed rape was investigated. parallel to trials, number deposited eggs assessed small boxes exposed field. Beetles released September laid significantly more compared beetles October, with maximum 270 per female. The resulted higher numbers larvae autumn, but this differed between years. Warm autumn or conditions led continued egg laying development, whereas cold stopped reproduction. Significant yield losses (25%) significant plant during were only found 2016/17 treatments an high (20 /m ). German threshold 3–5 reached when 13 before 20th m after September. Data study can be used for better prediction targeted control.