Non‐target effects of fungicides on nectar‐inhabiting fungi of almond flowers

Abstract

Nectar mediates interactions between plants and pollinators in natural and agricultural systems. Specialized microorganisms are common nectar inhabitants, and potentially important mediators of plant-pollinator interactions. However, their diversity and role in mediating pollination services in agricultural systems are poorly characterized. Moreover, agrochemicals are commonly applied to minimize crop damage, but may present ecological consequences for non-target organisms. Assessment of ecological risk has tended to focus on beneficial macroorganisms such as pollinators, with less attention paid to microorganisms. Here, using culture-independent methods, we assess the impact of two widely-used fungicides on nectar microbial community structure in the mass-flowering crop almond (Prunus dulcis). We predicted that fungicide application would reduce fungal richness and diversity, whereas competing bacterial richness would increase, benefitting from negative effects on fungi. We found that fungicides reduced fungal richness and diversity in exposed flowers, but did not significantly affect bacterial richness, diversity, or community composition. The relative abundance of Metschnikowia OTUs, nectar specialists that can impact pollination, was reduced by both fungicides. Given growing recognition of the importance of nectar microorganisms as mediators of plant-pollinator mutualisms, future research should consider the impact of management practices on plant-associated microorganisms and consequences for pollination services in agricultural landscapes.

Bacterial communities associated with the surface of fresh sweet pepper (Capsicum annuum) and their potential as biocontrol

“…For habitats, diversity results were as expected, as it is well known that the organic matter in the soil is an important source of nutrients for microorganisms and contains higher levels of fungal and bacterial propagules than hydroponic systems 17 . The diversity in treatments is in agreement with a study by Schaeffer, et al 18 , which showed fungicides application on nectar have no observable effect on bacterial OTU richness or community compositions. Furthermore, higher bacterial populations observed on the immature (green) fruit surfaces compared to the mature samples corroborated with findings by Palumbo, et al 19 , who found greatest bacterial diversity on early summer mature almond fruits than on the late summer mature almonds.…”

Side Effects of Pesticides on the Olive Fruit Fly Parasitoid Psyttalia concolor (Szépligeti): A Review

“…Another important aspect to consider is that fungicides can reduce the diversity and richness of nectar microorganisms (fungus and bacteria) in flowers, which decreases nectar quality, sugar concentration or pH, having consequences for the feeding of natural enemies [104]. Therefore, consequences of the application of fungicides on parasitoids should be further studied.…”

Quantitative Assessment of Nectar Microbe-Produced Volatiles

“…All evidence suggests agricultural floral nectar regularly contains floral microorganisms (13,21,22), but their effects on plant reproduction and pollination are rarely considered. Reports in the literature are mixed: in wild herb populations, the presence of yeasts increased pollen transfer in one study, but reduced seed set in another (3,6).…”