The diamondback moth in Tunisia: risk analysis, and influence of biotic and meteorological parameters on its population dynamics

The diamondback moth (DBM), Plutella xylostella is a serious pest of crucifers causing enormous damages on different crops of Brassica genus. The present study evaluated the impact of meteorological parameters on the population dynamics of P. xylostella . During 2018, four sites in four different regions of Tunisia served for the study and two other different sites in 2019. Obtained results showed a variation in population dynamics of P. xylostella between different investigated sites and during both years. Appearance of the larvae in 2018 was registered in March and since February 2019. Most important peaks of larvae and pupae population were recorded during April and May. Results showed a correlation between meteorological parameters and pest occurrence, especially temperature where correlations were positive. Degree-Day Growth (DDG) analysis was demonstrated according to lower threshold of temperature of the pest. It was situated between 5.5 and 13 °C during March in 2018 and it started from 4.7 °C in February in 2019. Correlations and DDG determination permitted to identify critical periods of the pest outbreak for future management. Infestation rates were noted from first dates of appearance of the pest between March and April during 2018 and since February in 2019 reaching 90 to 100% by the end of observations. Parasitism of P. xylostella larvae and pupae reached high values (ranking between 70 and 100%) during April and May. The population dynamics of P. xylostella is characterized by seasonal changes in abundance caused by differences in meteorological parameters that could make its management and monitoring difficult.