Volatile chemical compounds: attractants or repellents to Falconia intermedia?

Volatile chemical compounds: attractants or repellents to Falconia intermedia?
Samella Ngxande
Biological Control Unit, Zoology and Entomology Department, Rhodes University

Lantana camara is one the most problematic invaders in South Africa invading forest edges, sand dunes and shorelines by forming impenetrable thickets. Lantana camara invasions degrade natural biodiversity, reduce the value of land and, as a consequence, it has been a target for biological control for over 50 years. Recent studies have shown that feeding by one of the agents released against L. camara, Falconia intermedia, induces anti-herbivory response through increased leaf toughness, trichome density and production of volatile chemicals by two varieties of this weed. However, it is not known what specific effects the induced volatile chemicals have on F. intermedia. This study investigated the effect(s) of F. intermedia feeding on the volatile organic chemicals emitted by L. camara varieties, previously unknown. It also sets out to identify the major chemical compounds emitted using Gas Chromatography Mass Spectrometry (GC-MS). Olfactometry assays were conducted to check the effect of different plant varieties on the behaviour of Falconia intermedia. Olfactometry tests are being used to compare the attractiveness of volatile compounds from damaged and undamaged plants to F. intermedia. Preliminary results have showed that 105 (70%) out of 151 insects tested were attracted to undamaged plants. When major chemical compounds have been identified by GC-MS, assays will be done to check the effect of each compound on behaviour of F. intermedia. Once complete, the study will be able to comment on whether volatile chemical compounds contained in L. camara repel biocontrol agents or attract their natural enemies.