(1st Place) Bumble bee pharmacies in your garden: Medicinal effects of cultivated basil (Ocimum basilicum) on a bumble bee parasite

Flowers produce a vast array of secondary chemicals which can have ecological consequences on pollinators that forage on them. One such consequence can be pollinator medication: floral phytochemicals can be bioactive against pollinator parasites, and may reduce infection or improve survival when consumed.

Here, we evaluated the medicinal effects of cultivated basil (Ocimum basilicum) on common eastern bumble bees (Bombus impatiens) infected with the trypanosome endoparasite Crithidia bombi. Basil varieties are bred to produce distinct flavors and scents, resulting in unique chemical profiles for each variety. Such chemical variation may result in differential effects of basil varieties on pollinator parasites. We planted six varieties of basil in enclosed plots and released Crithidia-infected bumble bees to forage exclusively on a single variety for one week. We also collected volatile organic compounds (VOCs) produced by basil flowers and used gas chromatography-mass spectrometry to characterize and quantify scent data.

We found that there were three “medicinal” basil varieties: bees foraging on these varieties had significantly lower parasite counts than those that foraged on other varieties. We identified five VOCs that differentiate “medicinal” varieties, including two previously known to be bioactive against Crithidia. These compounds are also produced by basil relatives in the mint family Lamiaceae, including native North American plants used in pollinator habitats. We hope to use these findings to encourage gardeners and farmers to plant medicinal Lamiaceae on their lands, including medicinal varieties of basil.