Pollinator visitation, floral microbes, and seed set of Penstemon strictus treated with a fungicide, an insecticide, and both chemicals

Rocky Mountain Penstemon (Penstemon strictus; N = 126), were transplanted into 11.35-liter plastic pots. Plants were assigned to one of three experimental treatments (fungicide, insecticide, or their combination) or to a water control. Treatment assignments were randomized within phenological stage (flowering, budding, or vegetative) and each treatment was replicated 32 times in a randomized block design (except block 32 which only had an insecticide and control plant). The insecticide was applied directly to the soil as the product “Bioadvanced Fruit, Citrus & Vegetable Insect Protection” (SBM Company, McClellan Park, CA) which contains 0.235% of the neonicotinoid imidacloprid as an active ingredient. The fungicide was applied as a foliar spray as the product “Bioadvanced Disease Control for Roses, Flowers, & Shrubs” which contains 2.9% tebuconazole as an active ingredient. These chemicals were applied according to the manufacturer’s protocols and two water controls (soil application and/or foliar spray) were also applied such that each plant received a soil application and foliar spray of some type.

We recorded flowering date, number of flowers per plant, plant height, and herbivory damage weekly. Herbivory damage was visually estimated as percent damage across the entire plant; this was later converted to a binary (yes/no) survey of presence of herbivory damage to account for observer bias. At the conclusion of the experiment, we collected and dissected all fruits so that seeds could be counted and weighed.