Exogenous Calcium Suppresses the Oviposition Choices of Frankliniella occidentalis (Thysanoptera: Thripidae) and Promotes the Attraction of Orius similis (Hemiptera: Anthocoridae) by Altering Volatile Blend Emissions in Kidney Bean Plants.

Frankliniella occidentalis is a destructive pest of horticultural plants, while Orius similis is a natural enemy of thrips. It has been demonstrated that exogenous calcium could induce plant defenses against herbivore attack. We examined whether CaCl 2 supplementation altered the volatile emissions of kidney bean plants, which influence the oviposition preference of F. occidentalis . We also assessed the influence of volatile cues on O. similis . Using Y-tube olfactometer tests, we found that exogenous CaCl 2 treatment inhibited the selectivity of F. occidentalis but attracted O. similis . In addition, CaCl 2 treatment reduced the oviposition preference of F. occidentalis . Gas chromatography-mass spectrometry analyses revealed that CaCl 2 treatment altered the number and relative abundance of the volatile compounds in kidney bean plants and that (E)-2-hexen-1-ol, 1-octen-3-ol, β-lonone, and (E,E)-2,4-hexadienal might be potential olfactory cues. Furthermore, the results of the six-arm olfactometer test indicated that 1-octen-3-ol (10 -2 μL/μL), β-lonone (10 -2 μL/μL), and (E,E)-2,4-hexadienal (10 -3 μL/μL) repelled F. occidentalis but attracted O. similis . Overall, our results suggested that exogenous CaCl 2 treatment induced defense responses in kidney bean plants, suggesting that CaCl 2 supplementation may be a promising strategy to enhance the biological control of F. occidentalis .