Contact Toxicity and Ovideterrent Activity of Three Essential Oil-Based Nano-Emulsions against the Olive Fruit Fly Bactrocera oleae

Giulia Giunti,Orlando Campolo,Emilio Lo Presti,Francesca Laudani,Monica Bacchi,Vincenzo Palmeri

doi:10.3390/horticulturae8030240

Giulia Giunti, Orlando Campolo + Show 4 more

Open Access

https://doi.org/10.3390/horticulturae8030240

Copy DOI

Abstract

The control strategies for the olive crop key pest, Bactrocera oleae, involve synthetic chemical insecticides and few eco-sustainable alternatives, such as ovideterrents and lures. In the last few decades, the interest concerning the formulation of botanical based biopesticides increased, but little research investigated the suitability of these approaches for B. oleae control. This research aimed to investigate the residual contact toxicity and the oviposition deterrence of three essential oil (EO)-based nano-emulsions (Pimpinella anisum, Foeniculum vulgare, Mentha × piperita) against B. oleae adult flies. All the nano-emulsions possessed optimal physical characteristics, with droplets dimensions ranging from 115 to 152 nm and low PDI values (<0.2), even after 1 year of storage. Although no notable residual contact toxicity was noted, all the tested formulations reduced the number of oviposition puncture in no-choice tests (percent repellence: mint < fennel < anise). In choice trials, olives treated with fennel and anise EO-formulations at the highest concentration (7.5%, 75 g of EO/L) were less attractive respect to control fruits and a significant reduction of olive punctures was recorded. Nano-biopesticides are promising eco-friendly tools to integrate B. oleae pest management programs and to reduce the use of harmful conventional active ingredients.

Highlights

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the worldwide key pest of olive crop; this species belongs to the Dacinae sub-family, is strictly monophagous and can develop exclusively inside the drupes of Olea species in field
The physical features of the developed nano-formulations showed that all the EObased nano-emulsions had nano-metrical droplet size and an optimal homogeneity, represented by the low polydispersity index (PDI) values
To the best of our knowledge, this study proved the repellency of two essential oil (EO)-based nanoemulsions toward the key pest species, Bactrocera oleae, for the first time, and determined the residual contact toxicity of the formulations against adult flies

Summary

Introduction

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the worldwide key pest of olive crop; this species belongs to the Dacinae sub-family, is strictly monophagous and can develop exclusively inside the drupes of Olea species in field. The flies of the Dacinae sub-family are generally present in the tropical regions, while B. oleae is abundant in the northern Mediterranean, causing severe yield reduction [1]. In this area, the olive fruit fly population increases during summer until the harvest season, producing from 2 to 7 generations per year [2]. The olive fruit fly population increases during summer until the harvest season, producing from 2 to 7 generations per year [2] The control of this pest relies on different approaches, including: (i) chromotropic and chemotropic traps, (ii) sex pheromones, (iii) attract and kill baits, (iv) chemical control remains the main strategy against this pest [3]. The most diffused oviposition deterrents are kaolin and copper compounds, allowing high-quality oil production but causing moderate harm toward non-target predators [7]

Objectives

Methods

Results

Discussion

Conclusion