Testing the Single and Combined Effect of Kaolin and Spinosad against Bactrocera oleae and Its Natural Antagonist Insects in an Organic Olive Grove

Abstract

The presence and infestation level of Bactrocera oleae was monitored in an organic olive orchard divided into differently treated parcels with kaolin (K), spinosad (S) and with kaolin and spinosad (K + S) in alternate rows. The treatments did not seem to affect olive fruit fly population dynamics, while statistically significant protective effects were recorded against total and harmful infestation, but not against the active one. Eventually, neither kaolin nor spinosad were shown to have a particular detrimental effect against naturally occurring B. oleae parasitoids.

Current Status of the Main Olive Pests: Useful Integrated Pest Management Strategies and Genetic Tools

“…In an attempt to avoid these drawbacks, the combined use of spinosad and kaolin was tested and proven to be an effective strategy to control this pest in organic olive groves. The combined treatment reduces the total and damaging infestation, but not the active infestation, without adversely affecting the natural agonists of the olive fruit fly [160].…”

“…The first forms of control in olive groves included the anticipation of the harvest and the use of mixtures based on copper, cobalt, potassium/sodium arsenite, or tar [160]. In fact, some of these, although valuable [161], are not approved under the CE Nº1107/2009 regulation or are candidates for replacement in some European countries, such as Spain [10].…”

“…However, spinosad has an undesirable effect on populations of natural enemies of the olive fly, mainly on predatory arthropods inhabiting the tree canopy but also pollinators such as Apis mellifera or natural enemies of some other pests [172][173][174][175][176]. Nevertheless, sustainable olive grove management holds the potential to alleviate this adverse impact, as it distinctly enhances various soil quality parameters, encompassing the abundance and diversity of microbial and pedofaunal communities [160,177,178].…”

“…It is often applied to plants as a thin film that does not interfere with plant respiration, and once the water evaporates, it forms a protective barrier that acts as a physical barrier to pests [181]. When insects come into contact with the kaolincoated surfaces, they find it difficult to move and feed, which can help to reduce the populations of a wide range of insect pests in a wide variety of crops, including olive groves [160,161,[182][183][184][185][186][187]. One of the main advantages of using kaolin in IPM is that it does not leave harmful residues on the products and even mitigates the deleterious effect of drought on some plants [188,189].…”

“…However, it contains aluminium, which has raised concerns about how it ends up in the food chain and how it affects human health [190,191], and even kaolin is generally considered safe for beneficial insects, pollinators, and other non-target organisms [192]; this should be taken with caution [161,193]. Additionally, kaolin's effectiveness may vary depending on the pest species and the environmental conditions [160,192].…”