Efficiency of plant induced volatiles in attracting Encarsia formosa and Serangium japonicum, two dominant natural enemies of whitefly Bemisia tabaci in China
Whitefly Bemisia tabaci is a globally distributed and most destructive pest to agriculture. Owing to increasing chemical resistance, a long-lasting strategy to manage this pest must involve biological control. Herbivore-induced plant volatiles (HIPVs) usually play a profoundly important role in the foraging behaviour of natural enemies. Here, the effects of HIPVs from Chinese broccoli on the foraging behaviour of two dominant natural enemy species of B. tabaci in China, Encarsia formosa and Serangium japonicum, were investigated using a four-arm olfactometer, and exogenous jasmonic acid (JA) was used to induce plant volatiles to mimic the damage of the herbivore pest.
The parasitoid E. formosa was found to be more attracted by the volatiles from JA-induced broccoli than those from control plants. The residence times of E. formosa in the final-choice areas closed to volatiles from shoot JA (SJA)- and root JA (RJA)-induced plants were 119.8 ± 35.2 s and 99.8 ± 34.7 s respectively in the dual-choice experiments, and 123.8 ± 32.0 s and 102.3 ± 28.7 s respectively in the three-choice experiment. All are significantly longer than those spent in the final-choice area closed to volatiles from control plants (CON). JA-induced volatiles were also only a little more attractive to the predator S. japonicum. However, there was no significant difference between each of the two natural enemies in residence time spent in the final-choice areas closed to SJA, RJA or CON volatiles in both the dual- and three-choice experiments. Furthermore, the number of times that the parasitoid or predator entered the SJA, RJA and CON final-choice areas was not significantly different in any of the experiments.
The present results indicate that RJA- and SJA-induced plant volatiles have higher efficiencies in attracting the natural enemies of whitefly B. tabaci. The attractive efficiencies varied according to the plant volatiles that JA induced, and also depended on the natural enemy species. The parasitoid E. formosa seems to be more sensitive to and attracted by the induced volatiles than the predator S. japonicum. © 2014 Society of Chemical Industry