Emission of Volatile Compounds from Apple Plants Infested with Pandemis heparana Larvae, Antennal Response of Conspecific Adults, and Preliminary Field Trial

Abstract

This study investigated the volatile emission from apple (Malus x domestica Borkh., cv. Golden Delicious) foliage that was either intact, mechanically-damaged, or exposed to larval feeding by Pandemis heparana (Denis and Schiffermüller) (Lepidoptera: Tortricidae). Volatiles were collected by closed-loop-stripping-analysis and characterized by gas chromatography-mass spectrometry in three time periods: after 1 h and again 24 and 48 h later. Volatiles for all treatments also were monitored continuously over a 72-h period by the use of proton transfer reaction - time of flight-mass spectrometry (PTR-ToF-MS). In addition, the volatile samples were analyzed by gas chromatography-electroantennographic detection (GC-EAD) using male and female antennae of P. heparana. Twelve compounds were detected from intact foliage compared with 23 from mechanically-damaged, and 30 from P. heparana-infested foliage. Interestingly, six compounds were released only by P. heparana-infested foliage. The emission dynamics of many compounds measured by PTR-ToF-MS showed striking differences according to the timing of herbivory and the circadian cycle. For example, the emission of green leaf volatiles began shortly after the start of herbivory, and increased over time independently from the light-dark cycle. Conversely, the emission of terpenes and aromatic compounds showed a several-hour delay in response to herbivory, and followed a diurnal rhythm. Methanol was the only identified volatile showing a nocturnal rhythm. Consistent GC-EAD responses were found for sixteen compounds, including five aromatic ones. A field trial in Sweden demonstrated that benzyl alcohol, 2-phenylethanol, phenylacetonitrile, and indole lures placed in traps were not attractive to Pandemis spp. adults, but 2-phenylethanol and phenylacetonitrile when used in combination with acetic acid were attractive to both sexes.

Trapping Pandemis limitata (Lepidoptera: Tortricidae) moths with mixtures of acetic acid, caterpillar-induced apple-leaf volatiles, and sex pheromone

“…The experiment with rubber septa lures clearly showed that 2-phenylethanol alone is an ineffective attractant of P. limitata, whereas acetic acid appeared weakly attractive as it is for several tortricid species (Knight et al 2014). These results are consistent with European studies showing that 2-phenylethanol was not attractive to Pandemis species when used alone (Giacomuzzi et al 2016). However, unlike Pandemis species in the European study (Giacomuzzi et al 2016), P. limitata moths were caught significantly more often with acetic acid + 2-phenylethanol than they were with acetic acid + phenylacetonitrile.…”

“…European studies have thoroughly characterised the volatiles released by apple leaves in response to larval feeding by Pandemis heparana Denis and Schiffermüller (Giacomuzzi 2010;Giacomuzzi et al 2013Giacomuzzi et al , 2016. Among the many compounds emitted by apple leaves, six were considered unique and only released in response to herbivory.…”

“…Subsequent field trials revealed that none of the individual apple-leaf volatiles was attractive to a mixed population of P. heparana and P. cerasana (Hübner) (Giacomuzzi et al 2016). Yet, when phenylacetonitrile and 2-phenylethanol were individually combined with acetic acid, each binary blend caught a similar number of moths and each caught significantly more moths than their individual components (Giacomuzzi et al 2016). In a similar study focussed on the North American tortricid species, Spilonota ocellana (Denis and Schiffermüller) and C. rosaceana, El-Sayed et al (2016) recorded incidental catches of two nontarget species, P. limitata and P. pyrusana, using binary blends of acetic acid and these same aromatic benzenoids.…”

Importance of trap liner adhesive selection for male moth catch (Lepidoptera: Tortricidae) with bisexual attractants

“…Monitoring adult tortricid pests with traps is a key component of deciduous tree fruit management (Witzgall, Kirsch, & Cork, ). Sex pheromone lures have primarily been used to monitor males of these species, and more recently bisexual kairomonal attractants have been developed for the key tortricid pests (Giacomuzzi et al., ; Knight et al., ; Light et al., ). While a few studies have suggested that male captures in traps baited with kairomones could be influenced by previous female captures, this factor has not previously been evaluated experimentally.…”

“…An increasing body of research has developed bisexual attractants for key tortricid pests of apple Malus domestica Borkhausen, using host plant volatiles and/or microbial‐based compounds (codling moth: Light et al., ; Landolt, Suckling, & Judd, ; Landolt et al., ; leaf rollers: Giacomuzzi et al., ; Giacomuzzi, Mattheis, Basoalto, Angeli, & Knight, ; Judd, Knight, & El‐Sayed, 2017a, 2017b; Basoalto et al., ; oriental fruit moth: Mujica et al., ). The ability of pest managers to monitor female moth populations can increase the precision in tracking the pest phenology and improve timing of control tactics (Knight & Light, 2005a).…”