Degree-day risk thresholds for predicting the occurrence of Anarsia lineatella, Grapholita molesta and Adoxophyes orana in northern Greece peach orchards

Abstract

In the present work, the phenology of the most important peach pests was studied to estimate the risk thresholds to be used in applying an updated automatic pest management decision support system. Particularly, the seasonal occurrence of Anarsia lineatella, Grapholita molesta and Adoxophyes orana was determined during 2018 and 2020 using pheromone traps from April till October in eight peach orchards in the prefecture of Pella in northern Greece. Additionally, the accumulated degree-days (DDs) were calculated for each moth and further related to the seasonal flight patterns to determine the period of which the activity of each species starts as well as the period of the moth population peak. Moth capture data of one more year, 2021, were used to validate the risk threshold predictions. In most cases, the risk threshold predictions were at acceptable levels and especially in forecasting the start and the peak of the first and second flight period of the above three species. The first captures of A. lineatella, G. molesta and A. orana, early in the season were observed at 70, 33 and 362 DDs, respectively (lower temperature thresholds: 11.4 °C, 9.5 °C and 7.2 °C, for A. lineatella, G. molesta and A. orana, respectively, and Biofix: 1<sup>st</sup> of January in all the cases). The highest number of moth captures of A. lineatella, G. molesta and A. orana were observed at 150.6, 77.9 and 428.7 DDs, while the start of the subsequent second flight was observed at 365, 133 and 362 DDs, respectively. Moreover, the peak of the second moth flight was observed at 511.5, 204.8 and 1 239.5 DDs, for A. lineatella, G. molesta and A. orana, respectively. The current degree-day risk thresholds can be used for the precise timing of pesticides and are a prerequisite to implement automated real time decision support systems at a farm level.