If any of these flowering weeds are present at noticeable levels, it may be wise to avoid treating the area with a neonicotinoid (or any other insecticide). In the case of neonicotinoids (imidacloprid, clothianidin, thiamethoxam, dinotefuran), mowing off the flowers before application may not be enough since these insecticides are systemic and may be taken up by the plant and translocated to the flowers when another flush of growth occurs. Lawns that are relatively weed free should not pose a substantial risk to pollinators should a neonicotinoid be applied. Effective weed control should be a prerequisite for using neonicotinoid insecticides. We simply don’t know how much of the material ends up in the pollen and nectar of our most common weeds, but if there are no flowering weeds to take up the insecticide, the risk to pollinators will be significantly reduced. Always avoid spraying insecticide of any type directly onto plant blooms.
Doug Richmond, Turf Entomologist