Climate Change and Major Pests of Mediterranean Olive Orchards: Are We Ready to Face the Global Heating?

Abstract

Evidence of the impact of climate change on natural and agroecosystems is nowadays established worldwide, especially in the Mediterranean Basin, an area known to be very susceptible to heatwaves and drought. Olea europaea is one of the main income sources for the Mediterranean agroeconomy, and it is considered a sensitive indicator of the climate change degree because of the tight relationship between its biology and temperature trend. Despite the economic importance of the olive, few studies are nowadays available concerning the consequences that global heating may have on its major pests. Among the climatic parameters, temperature is the key one influencing the relation between the olive tree and its most threatening parasites, including Bactrocera oleae and Prays oleae. Therefore, several prediction models are based on this climatic parameter (e.g., cumulative degree day models). Even if the use of models could be a promising tool to improve pest control strategies and to safeguard the Mediterranean olive patrimony, they are not currently available for most O. europaea pests, and they have to be used considering their limits. This work stresses the lack of knowledge about the biology and the ethology of olive pests under a climate change scenario, inviting the scientific community to focus on the topic.

Keywords: Bactrocera oleae; Mediterranean Basin; Olea europaea; climate emergency; olive pest.

Figure 1

Long-term climatic data are the basis of insect pest prediction models together with insect data obtained by proper monitoring [40]. The decision support systems (DSSs), which bridge the gap between prediction models and extension services, have the task of technically supporting farmers in olive orchard management. In order to abandon scheduled treatments and then to avoid the risk of carrying out unnecessary chemical uses, farmers need a good scenario of the current status of the pest and its potential future trend. As a consequence of a conscious olive orchard management, positive outcomes on the environmental impact and global heating can be recorded (e.g., less air pollution) [49,54,55,96].

Figure 2

The tritrophic interaction of Dasienura oleae (Diptera: Cecidomyiidae), its parasitoids and the olive tree could be hypothetically altered by global heating. Under increasing temperature (atmosphere and soil), the olive tree starts suffering, and the production of secondary metabolites and other plant defensive traits (e.g., the phenomena of “talking tree” (host–host) and “crying for help” (host–parasitoids)) may be affected [2]. This may cause a disequilibrium of the tritrophic interaction and the consequent occurrence of pest outbreaks [2,100].