Subterranean Volatile Increases Biological Control Figure 1. Time course of pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene) release following initiation of weevil (Diaprepes abbreviatus) feeding on citrus roots. Insert in the upper right displays chromatogram of volatile abundance at each interval. doi:10.1371/journal.pone.0038146.g001 Figure 2. Optimal dosage of pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene) for attracting entomopathogenic nematodes (Steinernema riobrave and Heterorhabditis indica) based on the log scale dilution of purified compound. Picture in upper left displays sand-filled two-choice olfactometers used for nematode bioassays. doi:10.1371/journal.pone.0038146.g002 PLoS ONE | www.plosone.org 3 June 2012 | Volume 7 | Issue 6 | e38146