Evaluation of the effect of agroclimatic variables on the probability and timing of olive fruit fly attack

Abstract

Agroclimatic variables may affect insect and plant phenology, with unpredictable effects on pest populations and crop losses. Bactrocera oleae Rossi (Diptera: Tephritidae) is a specific pest of Olea europaea plants that can cause annual economic losses of more than one billion US dollars in the Mediterranean region. In this study, we aimed at understanding the effect of olive tree phenology and other agroclimatic variables on B. oleae infestation dynamics in the Umbria region (Central Italy). Analyses were carried out on B. oleae infestation data collected in 79 olive groves during a 7-year period (from 2015 to 2021). In July-August, B. oleae infestation (1% attack) was negatively affected by altitude and spring mean daily temperatures and positively by higher winter mean daily temperatures and olive tree cumulative degree days. In September-October, infestation was negatively affected by a positive soil water balance and high spring temperatures. High altitude and cumulative plant degree days were related to delayed attacks. In contrast, high winter and spring temperatures accelerated them. Our results could be helpful for the development of predictive models and for increasing the reliability of decision support systems currently used in olive orchards.

Keywords: Bactrocera oleae; Diptera; Oleaceae; Tephritidae; insect monitoring; oviposition; pest management.

Figure 1

Relationships between infestation probability or Julian day of occurrence of Bactrocera oleae and some of the variables retained in the best-fitted models of Tables 2 – 5 . Curves represent the model estimate (solid line) and 95% confidence intervals (shaded area). For each plot, the variables not represented were set to their average value on the original scale (reported in the caption of Tables 2 – 5 ). Tick symbols represent the distribution of the original data. Explanatory variables are described in Table 1 .