1. Interactions between plants and natural enemies of insect herbivores influence plant productivity and survival by reducing herbivory. Plants attract natural enemies via herbivore-induced plant volatiles (HIPVs), but how water availability (WA) influences HIPV-mediated defenses is unclear. 

2. We use tomato (Solanum lycopersicum), tomato fruitworm (Helicoverpa zea), and two natural enemies, the parasitoid wasp (Microplitis croceipes) and the predator spined soldier bug (Podisus maculiventris), to investigate the effect of WA on HIPV emission dynamics and associated plant defense. 

3. We show that low WA initially increases total HIPV emission by tomatoes on the first day of herbivore exposure and, in contrast, reduces HIPV emission on the second day. Low WA enhances HIPVs that are mostly found in tomato trichomes. Notably, some volatiles inhibited by low WA are known attractants of natural enemies. Evidence from Y-tube and in-cage behavioral assays indicates that changes in HIPV emissions by low WA compromise the ability of tomato plants to attract natural enemies. 

4. Synthesis: Based on our results, we propose a hypothesis where plants respond to low WA by enhancing repellent HIPV emissions and reducing the emission of HIPVs that attract natural enemies, which disrupts natural enemy-mediated plant indirect defenses but enhances plant direct defense against herbivores.

This dataset contains two main parts. The first half is GCMS data of plant volatiles collected under different treatments. The data were analyzed using the R code developed by us. The second part contains multiple behavioral data that were collected by human observation. The data were analyzed using the R code developed by us. Regarding detailed methodology, we refer the reader to the associated publication in the Journal of Ecology: Low water availability enhances volatile-mediated direct defenses but disturbs indirect defenses against herbivores. 

To open the data files, please install R language and R studio for R-related files (R markdown files and RData). You need Excel to open raw data files, and any website software to read to HTML files for analytical results.