Ornamental plants on sale to the public are a significant source of pesticide residues with implications for the health of pollinating insects

This study, performed in the United Kingdom, screened leaves, pollen and nectar of ornamental plants for eight insecticides and 16 fungicides used in nursery production. The researchers found that the ornamental plants, bought at retail outlets, were commonly contaminated with multiple pesticides. The analysis of leaves found at least one pesticide in 27 of the 29 plant species tested. Species contained as many as 10 pesticides. Neonicotinoids were found in 70% of the plants; the organophosphate chlorpyrifos was found in 10%; pyrethroid insecticides were found in 7%; and fungicides were detected in 38%. Pollen was taken from 18 plant species, and a total of 13 pesticides were detected. Systemic pesticides were found with greater frequency than contact and penetrant pesticides in pollen. There was a significant correlation between concentration of systemic pesticides in leaves and pollen. Chlorpyrifos (a contact poison) and three localized penetrant fungicides were also found in pollen. Still, there was not a significant correlation between either contact or local penetrant chemicals concentrations in leaves and pollen. Nectar samples were challenging to collect and only small quantities available. Nectar was taken from 11 plant species. Concentrations were below the method detection limit except for neonicotinoids which still had low detection levels.

The author’s findings suggest that honey bees are unlikely to receive lethal doses by foraging on these ornamental plants in the short term. However, the levels detected do overlap with levels known to cause measurable harm to bees. Furthermore, since pesticides were frequently detected jointly, bees are likely exposed to a cocktail of chemicals, which could act additively or synergistically. The researchers theorized that large plant sales in spring could see pulse exposures at a critical time in bumble bee colony formation. Researchers were unable to evaluate whether the net effect of planting pesticide contaminated “pollinator friendly” flowers is positive or negative. Researchers suggested that if people want to avoid contaminated flowers they should grow plants from seed, buy from organic nurseries or swap plants with other people.

Authors: 
Lentola, A., A. David, A. Abdul-Sada, A. Tapparo, D. Goulson, and E. M. Hill
Journal: 
Environmental Pollution
Year published: 
2017