Olive Landscape Affects Bactrocera oleae Abundance, Movement and Infestation

Marta Ortega,Cristina E Fernández,Natalia Moreno,Susana Pascual

doi:10.3390/agronomy12010004

Abstract

The economic importance of Bactrocera oleae (Rossi) and the problems associated with insecticides make necessary new management approaches, including deeper biological knowledge and its relationship with landscape structure. Landscape complexity reduces B. oleae abundance in late summer–autumn in areas of high dominance of olive groves, but the effect of landscape structure in spring and in areas less dominated by olive groves has not been studied. It is also unknown whether the insect disperses from olive groves, using other land uses as a refugee in summer. This work evaluates the effect of landscape structure on olive fruit fly abundance and movement in spring and autumn, and infestation in autumn, in central Spain, an area where the olive crop does not dominate the landscape. A cost–distance analysis is used to evaluate the movement of the fly, especially trying to know whether the insects move away from olive groves in summer. The results indicate that B. oleae abundance is consistently lower in complex landscapes with high scrubland area (CAS), patch richness (PR) and Simpson landscape diversity index (SIEI), and low olive grove area (CAO). The cost–distance analysis shows that the fly moves mainly in spring, and amongst olive groves, but there is no evidence that land uses other than olive groves serve as a summer refuge. Olive fly infestation decreased with decreasing CAO and increasing CAS and SIEI, accordingly with the effect of landscape on abundance. Thus, mixing olive groves with other land uses, which are not a source of flies, can help improve control of this important pest.

Highlights

The olive fruit fly, Bactrocera oleae, is the key pest of olive crops in most olive growing areas worldwide [1]
The results indicate that B. oleae abundance is consistently lower in complex landscapes with high scrubland area (CAS), patch richness (PR) and Simpson landscape diversity index (SIEI), and low olive grove area (CAO)
Assessment of B. oleae Movement The models were fitted to compare the effect of landscape on B. oleae abundance from an area approach, i.e., using CAO as the landscape explanatory variable, and from a dynamic approach, i.e., using mean cost–distance values (COST) as explanatory variables (Tables 2 and 3)

Summary

Introduction

The olive fruit fly, Bactrocera oleae, is the key pest of olive crops in most olive growing areas worldwide [1]. In areas with mild winter temperatures B. oleae may overwinter as a larva or an adult. The biology of overwintering populations has been studied, showing the presence of a complete generation in the spring [6]. The number of B. oleae adults captured by different trap devices in olive groves decreases to minimum values, and increases from late summer to autumn, when olive fruit fly damage occurs. Studies on B. oleae abundance have been conducted mainly on autumn populations, with a need to clarify the biological aspects of spring populations [6]. It is important to try to clarify the biology of B. oleae in the summer, as it is unclear whether the unfavourable effects of high temperature and low humidity cause the fruit fly to disperse to cooler sites [1]

Objectives

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Results

Conclusion