Testing a delay differential equation model for the population dynamics of Frankliniella occidentalis in table grape vineyards of Southern Italy

The western flower thrip (WFT) Frankliniella occidentalis infests several crops and it is included in the EPPO A2 list. Polyphagia and a spread of approximately 230 km/year support the diffusion of this pest in Europe since 1980. Besides the direct damage caused to host plants, WFT is also a vector of tospoviruses, such as the tomato spotted wilt virus. The management of this pest is complex and would benefit from mathematical models that could simulate the infestation trends. This work applies a general modelling framework based on delay differential equations (DDEs) to the specific case of WFT, considering metrological aspects connected with the monitoring techniques applied, as well. Temperature-dependent biodemographic rate functions were parametrised by using life tables data retrieved through a systematic literature review. A preliminary model evaluation was conducted by comparing model simulations and field populations of nymphs and adults collected in several Apulian locations, over different years, on organic table grape orchards. Results showed a good overlap between the simulated and the experimental populations of nymphs and adults, although the overall average number of individuals was low in most of the orchards. This study provides a valuable foundation for further improvements of the model, which should be directed towards more accurate biological information on the response of the species to additional environmental variables besides temperature.