Free fatty acids from the weed, Polygonum orientale leaves for attraction of the potential biocontrol agent, Galerucella placida (Coleoptera: Chrysomelidae)

Abstract

Extraction, thin layer chromatography and gas chromatography-mass spectrometry of leaf surface waxes of Polygonum orientale L. (Polygonaceae) weed revealed 11, 15 and 11 free fatty acids in young, mature and senescent stages. Oleic acid was the predominant in young leaves (5950 ± 111 µg); whereas palmitic acid was the predominant fatty acids, representing 4247.5 ± 23 and 6644 ± 110 µg in mature and senescent leaves, respectively. Both tridecanoic and heneicosanoic acids were not detected in young and senescent leaves, and myristic and heptadecanoic acids were not identified in young leaves; whereas lauric and nonadecanoic acids were not detected in senescent leaves. The free fatty acids from young, mature and senescent weed leaves, and the mixtures of synthetic fatty acids mimicking free fatty acids of three types of weed leaves attracted female Galerucella placida (Coleoptera: Chrysomelidae) at the minimal amounts of 2, 1 and 2 leaf equivalent free fatty acids, respectively, in Y-shaped glass tube olfactometer bioassays under laboratory conditions. Individual synthetic pentadecanoic, palmitoleic, stearic, nonadecanoic and docosanoic acids at 44.82, 9.91, 92.22, 18.33 and 15.88 µg, respectively, elicited attraction of the insect. A synthetic blend of 3.59, 7.89, 44.82, 9.91, 32.31, 18.33 and 15.88 µg of lauric, myristic, pentadecanoic, palmitoleic, heptadecanoic, nonadecanoic and docosanoic acids, respectively, indicated highest attraction of the insect.

Keywords:

• Polygonum orientale leaves
• Free fatty acids
• Galerucella placida
• Y-shaped glass tube olfactometer
• bioassay

Acknowledgements

We thank Dr. Mark S. Goettel and anonymous reviewer(s) for helpful suggestions of an earlier version of the manuscript. We are thankful to C. L. Staines, National Museum of Natural History, Smithsonian Institution, Washington, DC for identifying the insect, and Prof. Ambarish Mukherjee of this University for identification of the weed. The financial assistance from the University Grants Commission, New Delhi, India as a JRF (F1-17.1/2013-14/RGNF-2013-14-SC-WES-38778/ (SA-III/Website) to Ujjwal Malik is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here: http://dx.doi.org/10.1080/09583157.2014.1000264