Effects of optical brighteners used in biopesticide formulations on the behavior of pollinators

A patent has been granted for the formulation of baculoviruses with stilben e-derived optical brighteners, a group of compounds that absorb ultraviolet (UV) radiation and emit visible blue wavelengths. These compounds are bein g extensively tested for control of forest-feeding lepidopterous insects in North America; optical brighteners may thus become a common ingredient in commercial baculovirus formulations in the near future. Many flower species use UV signals to attract insects and to direct them to the nectaries. We examined a possible consequence of field applications of optical brightener s: their effects on the ability of pollinators to find and handle flowers. In field studies carried out in Mexico and the United Kingdom on three diff erent flower species, application of dilute (0.1% or 1%) concentrations of the optical brightener Tinopal CBS reduced recruitment of bees to flowers. Bees that approached flowers were less likely to land and feed on flowers t reated with Tinopal than on controls. On one plant species, Trifolium repen s, the time taken for bees to handle inflorescences was longer following ap plications of Tinopal. It seems that this optical brightener may both reduc e recruitment of insects to flowers and interfere with their ability to loc ate rewards. Field-scale applications could reduce pollination of crops, we eds, and wildflowers and adversely affect bee populations. These possibilit ies should be examined in more detail before widespread applications of the se compounds to the environment are made. (C) 2000 Academic Press.