The Role of Leaf Volatiles of Ludwigia octovalvis (Jacq.) Raven in the Attraction of Altica cyanea (Weber) (Coleoptera: Chrysomelidae)

Abstract

Larvae and adults of Altica cyanea (Weber) (Coleoptera: Chrysomelidae) feed on the rice-field weed Ludwigia octovalvis (Jacq.) Raven (Onagraceae), commonly known as willow primrose, which is considered a biocontrol agent of the weed. Volatile organic compounds from undamaged plants, plants after 4, 12, and 36 h of continuous feeding by A. cyanea larvae or adult females and after mechanical damaging were identified by GC-MS and GC-FID analyses. Twenty nine compounds were identified from undamaged plants. 2Z-Penten-1-ol, geraniol, and 1-tridecanol were present in all plants damaged by larvae. In contrast, feeding by adults caused the release of 2Z-penten-1-ol only after 12 and 36 h; whereas geraniol and 1-tridecanol appeared only after 36 h. Farnesyl acetone was detected after 12 and 36 h of feeding by larvae and after 36 h of feeding by adults. Farnesene was detected after 36 h of feeding by larvae and adults. Linalool was unique after 36 h of feeding by larvae. In Y-shaped glass tube olfactometer bioassays, A. cyanea females were attracted to volatiles after 36 h of feeding by larvae or adults compared to volatiles released by undamaged plants. The insects were attracted to five synthetic compounds: 3-hexanol, α-pinene, linalool oxide, geraniol, and phytol. Synthetic blends were more attractive than individual compounds. Compared to undamaged plants, volatiles released by plants, damaged by conspecific individuals, were more attractive to A. cyanea females, due to elevated emissions of 3-hexanol, α-pinene, linalool oxide, geraniol, and phytol.

Attraction of the potential biocontrol agent Altica cyanea by volatile compounds of three species of Ludwigia weeds from rice fields

“…We have previously demonstrated that herbivore-induced plant volatiles (HIPVs) from 10-leaf-stage L. octovalvis when fed by A. cyanea adults or larvae for 36 h were attractive to A. cyanea females compared to undamaged L. octovalvis (Mitra et al, 2017a). Furthermore, in our previous study, we identified 30 headspace compounds of L. octovalvis after 12 h of feeding by A. cyanea adults, and four more (geraniol, a-farnesene, 1-tridecanol, and farnesyl acetone) after 36 h of feeding (Mitra et al, 2017a). In the current study, we allowed A. cyanea adults to feed continuously for 48 h on L. octovalvis to see whether more feeding could induce extra volatile compounds.…”

“…VOCs emitted from plants can serve as cues for host finding, feeding, and oviposition by herbivorous insects (Bruce et al, 2005;Bruce & Pickett, 2011). We have previously demonstrated that herbivore-induced plant volatiles (HIPVs) from 10-leaf-stage L. octovalvis when fed by A. cyanea adults or larvae for 36 h were attractive to A. cyanea females compared to undamaged L. octovalvis (Mitra et al, 2017a). Furthermore, in our previous study, we identified 30 headspace compounds of L. octovalvis after 12 h of feeding by A. cyanea adults, and four more (geraniol, a-farnesene, 1-tridecanol, and farnesyl acetone) after 36 h of feeding (Mitra et al, 2017a).…”

“…A Y-tube olfactometer (stem and arms 15 cm long, 0.6 cm radius, and 45°angle between the arms) was used to study behavioural responses of A. cyanea females using the method adapted from Mitra et al (2017a). The stem of the olfactometer was connected to a porous glass vial (1 cm radius, 3 cm long) and the test insect was released into this porous glass vial.…”

“…Plant volatiles can be used for monitoring insects in biocontrol programmes (Padovan et al, 2010;Piesik et al, 2012;Smith & Beck, 2013;Wheeler & Schaffner, 2013). Furthermore, volatiles from L. octovalvis plants that were fed upon by adults of A. cyanea for 6 and 48 h were identified and quantified through GC-MS and GC-FID analyses, respectively, and their role in attraction of A. cyanea to L. octovalvis was established (Mitra et al, 2017a). Furthermore, volatiles from L. octovalvis plants that were fed upon by adults of A. cyanea for 6 and 48 h were identified and quantified through GC-MS and GC-FID analyses, respectively, and their role in attraction of A. cyanea to L. octovalvis was established (Mitra et al, 2017a).…”

“…As host preference of A. cyanea has not been reported, nor the role of volatiles from the three Ludwigia species, we identified and quantified volatiles in situ from undamaged L. octovalvis plants through gas chromatography-mass spectrometry (GC-MS) and GC-flame ionization detection (GC-FID) analyses, respectively. Furthermore, volatiles from L. octovalvis plants that were fed upon by adults of A. cyanea for 6 and 48 h were identified and quantified through GC-MS and GC-FID analyses, respectively, and their role in attraction of A. cyanea to L. octovalvis was established (Mitra et al, 2017a). A preliminary study indicated that L. adscendens plants in the 10-leaf stage fed by A. cyanea for 48 h were too small to collect volatiles from.…”