Liriomyza trifolii, a leaf miner, is a serious pest of many glasshouse crops and effective control measures are needed urgently. One promising approach is to use compounds that occur naturally in plants. In the research reported here, leaves of Drosophyllum lusitanicum, an insectivorous plant, were used as they contain "plumbagin", a compound that has various biological activities.
The plant is native to the Algarve in Portugal. Leaves were collected from the wild, dried at 40 degsC for two days, powdered, and then extracted with n-hexane. Plant shoots were also multiplied in a tissue-culture system before being extracted. Adult female leaf miners were collected in the laboratory and kept unfed until the experiments started. Plant extracts of different concentrations were produced and tested in a contact assay. All insects that were in contact with the highest concentration of plant extract died within a day. Insects that were fed the plant extract also died but more slowly.
"Plumbagin" was the main insecticidal compound present but its effectiveness was probably enhanced by other, minor components of the extract. Encouragingly, suitable plant material could be multiplied using tissue-culture techniques as this should ensure that the wild populations of the plant and its natural habitat are not damaged.
Insecticidal Activity of Leaf Extracts from Drosophyllum lusitanicum against Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) by Goncalves, Goncalves, Ameixa, Nogueira and Romano (2008). Journal of Horticultural Science & Biotechnology 83 (5): 653-657. The authors' abstract of their manuscript can b e seen in full at www.jhortscib.com.