A new paper in PNAS Nexus, published by Oxford University Press, indicates that chemicals used in agriculture, like fertilizers and pesticides, can change the way bees ‘see’ a flower and that this reduces the number of bees visiting a flower.
Flowers produce a diverse range of cues and attractants to insects that promote feeding and pollination. Bees use color, sun, and magnetic fields to navigate the landscape. On a smaller scale, they use cues like flower odor and color, but also humidity and electric fields to identify plants. Farmers apply mixtures of chemicals, in particular fertilizers, on plants routinely using large-scale spray applications. The widespread use of chemicals in agriculture and horticulture is a substantial source of pollution and has been linked to reductions in bee population size and diversity.
While researchers have long recognized that many of these chemicals are toxic, they know little about how agrochemicals affect the immediate interaction between plants and pollinators. Spray applications can change the properties of flowers in several ways. Many agricultural chemicals carry an electric charge designed to adhere to plants. Thus, spray applications can potentially change the electric fields surrounding a flower. A big question is thus whether agrochemical application can distort floral cues and modify behavior in pollinators like bees.
Researchers here tested the effect of fertilizer sprays on various floral cues used by bees. They observed that the chemical did not affect vision and smell but that there was a response in the electric field surrounding the flower. To visualize this, the researchers sprayed cut flowers with positively charged, colored particles released as an aerosol.
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