Research has confirmed a correlation between talc and seed treatment used in planters and honeybee deaths. The problem is neonicotinoids which are used in popular insecticidal seed treatments such as Gaucho, Cruiser or Poncho on corn and soybean seed. Analysis of bees found dead in and around Indiana hives showed a presence of neonicotinoids. Researchers at Purdue University also found clothianidin (Poncho) and thiamethoxam (Cruiser) at low levels in the soil -- up to two years after treated seed was planted.
According to Purdue Entomologist Christian Krupke, we hypothesize that planter box talc is responsible for a lot of the acute exposure, but we found insecticides virtually every place we looked, including pollen, dandelions and topsoil from unplanted fields. Krupke believes talc is a logical first target for remedial action since those concentrations were by far the highest found.
Krupke noted that most modern planters require talc to maintain proper seed flow. Talc can escape when loading planters, during planting and some remains in the system to be cleaned out. Krupke recommends that farmers use less than recommended rates. He says - in my personal experience, planting without talc leads to skips and doubles in the planted row. Treated seeds are sticky and talc is required to plant them properly.