Alpha-thujone prevents apple infestation by codling moth neonates, a study using comparative planar chromatography

Codling moth (Cydia pomonella) is a major pest of apples in both North America and Europe, capable of causing up to 40 billion dollars in crop damage each year. Control of this pest through traditional chemical means has proven difficult, as the neonates are only exposed to spray residues for a very brief period between hatching and infestation of the fruit.  In our lab we have been studying an alternative fruit protection strategy, using botanical feeding deterrents.

Here, we concentrated on feeding deterrent effects of crude extracts from various species of the genus Artemisia; A. absinthium, A. arborescens x absinthium, A. annua, and A. ludoviciana. The crude extracts of these species were subjected to comparative, qualitative high performance thin layer chromatography (HPTLC) in the presence of alpha-thujone standards.  The results of this analysis suggested presence of alpha-thujone in A. arborescens x absinthium extract, only.  Next, the stationary phase areas of the chromatograms co-localizing with alpha-thujone standards were scraped off the plate and separately collected from particular chromatogram lanes, each representing a different Artemisia species. Each sample of the stationary phase was then extracted with dehydration alcohol, evaporated, re-dissolved to a concentration of 10 mg/ml, and their potential for preventing apple infestation by codling moth neonates was evaluated in a double choice bioassays for feeding deterrence.  The extract isolated from A. arborescens x absinthium prevented fruit infestation by 22 of 24 codling moth neonates, while no other species showed any significant action, suggesting that alpha-thujone was responsible for feeding deterrence. Further experiments showed that isolated alpha-thujone indeed prevents fruit infestation by codling moth neonates in a concentration dependent manner (concentrations of 10, 30 and 100 mg/ml were effective). However, further analysis of feeding deterrent activity showed that crude extracts of A. arborescens x absinthium were effective at concentrations as low as 1 mg/ml, demonstrating that alpha-thujone is not the only feeding deterrent constituent of A. arborescens x absinthium.