Differences in the emission of volatile organic chemicals in Lantana camara and implications for biological control efforts

Differences in the emission of volatile organic chemicals in Lantana camara and implications for biological control efforts
Heshula L.U.P.1, Wheeler G.S.2
1 Rhodes University, Grahamstown, South Africa; 2 USDA, Invasive Plant Research Laboratory, FL, USA

Leaf chemistry is a critical factor in the location, suitability and preference of plants by insects. Volatile organic chemicals (VOCs) play an important role in mediating plant insect interactions, and could provide valuable insight into agents’ behaviour in weed biological control. Mechanical damage studies provide a quick way to detect any VOC changes, and are a useful tool to simulate herbivory. Experiments to measure the quantitative and qualitative effects on VOCs emission were conducted by imposing mechanical damage to leaves of intact Lantana camara plants. Solid-phase microextraction (SPME) and Gas Chromatography-Mass Spectroscopy (GC-MS) were used to evaluate VOCs profile differences between the different treatments. Results showed a general increase in total VOCs emitted after damage on day 2, with cut leaf damage and punctured leaf damaged treatments increasing by 92% and 45% respectively, compared to undamaged leaves measured on day 1, demonstrating the phenotypic plasticity of this weed. On day 3 a decrease in the quantity of VOCs released was seen with a reduction of 66% and 65% in cut and punctured leaf treatments, respectively, indicating the need for continuous damage for the induced responses to be sustained. These results indicate that damage caused by cutting leaf material elicit stronger L. camara VOC responses than leaf piercing damage, results that potentially hold important insights into the weed- agent interactions of cutting and piercing leaf feeders of L. camara. These results may have important implications for biological control agents’ performance pre- and post-release evaluation.