Bitter & sweet: Attraction of brown marmorated stink bugs to odorants from blooming sunflowers

The polyphagous brown marmorated stink bug (BMSB), Halymorpha halys Stål, has become a significant crop pest in its invaded ranges in North America and Europe. According to prior studies, winged adults select host plants at distinct phenological stages. Working with the sunflower, Helianthus annus, as our model plant, we tested the hypotheses (1) that BMSBs distinguish between phenological stages of sunflower (vegetative, pre-bloom, bloom, seeding), (2) that attraction to the preferred stage is mediated primarily by plant odorants, and (3) that synthetic plant odorants enhance the efficacy of synthetic BMSB aggregation pheromone as a trap bait. With evidence obtained in laboratory olfactometer bioassays suggesting that BMSBs prefer the blooming stage, we captured the headspace odorants of blooming sunflower on the adsorbent Porapak Q, analyzed aliquots of Porapak Q extract by gas chromatography-mass spectrometry, identified all odorants in the extract, and prepared a synthetic odorant blend for laboratory and field testing. This synthetic blend attracted BMSBs in laboratory olfactometer bioassays in the absence of visual sunflower cues, and in a field experiment, it significantly enhanced the effect of synthetic pheromone for attraction and capture of BMSBs.