Limits to monitoring risks of Bactericera trigonica (Hemiptera, Psylloidea) in carrot fields

Abstract: Although psyllids have long been known in carrot crops (Daucus carota L.) in France, their presence has only recently taken on a new dimension in Europe, related to the re-emergence of the transmission of a bacterium: Candidatus Liberibacter solanacearum. In France, the main psyllid species present in carrot fields is Bactericera trigonica Hodkinson, a plurivoltin species.The potential management of B. trigonica requires better knowledge of its biology in order to be able to determine the appropriate protection techniques at the right time. It is therefore necessary to establish the flight periods and to develop the ability to forecast them. On the CTIFL site of Lanxade (South-West France) the flying activities of B. trigonica were observed from 2014 to 2018. Moreover, in 2018, the populations present on the carrots were monitored.Concerning the flight periods, catches in greater or lesser quantities were made throughout the year, thus showing the potential presence of B. trigonica in carrot fields around the year. However, we recorded three periods of intense flight activity.Comparison of catch periods with traps and populations in carrots shows a good concordance with the first two flight peaks and a poor one with the third. Trapping is therefore a good way of predicting risks for the first half of the year, but it fails for autumn flights.