New Tools for Conservation Biological Control: Testing Ant-Attracting Artificial Nectaries to Employ Ants as Plant Defenders

Abstract

Knowledge of the role of ants in many agroecosystems is relatively scarce, and in temperate regions the possibility to exploit ants as biocontrol agents for crop protection is still largely unexplored. Drawing inspiration from mutualistic ant-plant relationships mediated by extrafloral nectaries (EFNs), we tested the use of artificial nectaries (ANs) in order to increase ant activity on pear trees and to evaluate the effects on the arthropods, plant health and fruit production. While EFNs secrete a complex solution mainly composed of sugars and amino acids, ANs were filled with water and sucrose only. The results suggest that ANs can be used as manipulative instruments to increase ant activity over long periods of time. High ant activity was significantly linked to lower incidence of the pathogen fungus Venturia pyrina (pear scab) on pear leaves, and of the presence of Cydia pomonella (codling moth) caterpillars on pear fruit production. These results further encourage exploring underrated possibilities in the development of new tools for conservation biological control (CBC).

Searching for new predators of the invasive Halyomorpha halys: the role of the black garden ant Lasius niger

“…However, under similar conditions C. scutellaris (another ant common in agroecosystems) had a greater impact (Castracani et al., 2017). This points out the need to consider the diversity in the behaviour and ecological roles of the various ant species as natural pest managers in agroecosystems (Hölldobler & Wilson, 1990; Way & Khoo, 1992; Maňák et al., 2013; Schifani et al., 2020). Ant diversity and ecology, different feeding habits, behavioural ecology, and impact on the dynamics of species assemblages and community structure, as well as specific climate and environmental factors, suggest the importance of considering both single species and community effect on herbivores in agroecosystems to better plan programs of conservation biological control and IPM involving ants (Gibb et al., 2017; Arnan et al., 2018; Castracani et al., 2020).…”

“…Among the various trophic roles, they are also predators of pest species (Cerdá & Dejean, 2011). This may represent an important service for plants hosting ants, for those that are more or less routinely visited by ants, or that are surrounded by ant colonies (Campolo et al., 2015; Giannetti et al., 2019; Schifani et al., 2020). Several ant species are robust predators or exhibit very aggressive reactions against other animals including herbivores (Hölldobler & Wilson, 1990).…”

First Report on the Acrobat Ant Crematogaster scutellaris Storing Live Aphids in Its Oak-Gall Nests

“…Later, the trees were isolated with adhesive strips (glue bands, Stocker art. 45118) at the base of the trunk to prevent any successive ant colonization [ 4 , 37 ]. The galls were left on the trees for one year before being retrieved (from September 2016 to October 2017, coinciding with the period of Crematogaster scutellaris (Olivier, 1792) nuptial flights and foundation of new colonies [ 38 ]).…”

Combatting plant diseases with ant chemicals: A review and meta‐analysis

“…Yet, several studies have shown reduced disease incidence on antpatrolled plants compared to plants without ants. These include a few studies on agricultural crops, such as apple, pear and mango, experiencing reduced scab symptoms Peng & Christian, 2005Schifani et al, 2020) as well as natural ant-plant symbioses, where plants are relieved from various plant diseases. A meta-analysis of such studies showed that ants may be as detrimental to plant pathogens as they are to arthropod herbivores .…”

“…Multiple studies show that the presence of ants can lead to reduced plant disease incidence. A recent review study identified 13 ant species that were able to control 14 fungal, oomycete and bacterial plant pathogens on 12 different plant species , and two subsequent studies showed reduced incidence of scab and fruit rot on ant associated apple and pear trees compared to control trees without ants Schifani et al, 2020). A further recent study showed that oak seedlings inhabited by ants showed reduced incidence of leaf fungal attacks compared to ant-free control seedlings (Giannetti et al, 2019).…”