The Evolution of Modern Seed Treatments

The history of seed treatment is one that dates back thousands of years but, like many areas impacted by innovation, the advancements in this technology have been most dramatic in recent decades. Thirty-five years ago, the majority of all seed was treated with products that had a mode of action limited to contact (non-systemic) activity and of short duration. Captan and thiram were the most commonly used fungicide seed treatments at that time and were used on both agronomic and vegetable seed to protect against seed-borne and soil-borne diseases. While this older chemistry offered benefits with regards to improved stand establishment, the length of protection was problematic. These early products were unable to provide protection against systemic infections and had minimal impact on post-emergent seedling diseases. The introduction of systemic fungicides provided the benefit of longer lasting systemic protection and they were quickly adopted by farmers. New products like carboxin were much more effective in controlling post-emergent seedling diseases such as rhizoctonia, and for the first time, offered effective protection against systemic seed-borne infections from diseases, such as loose smut in wheat and barley. During this same period, the use of seed treatment insecticides was much less common. The organochlorines, lindane and heptachlor, and the organophosphates, diazinon and chlorpyrifos, were used selectively as seed treatments for protection against soil-borne insects such as wireworm (Agriotes spp), white grubs (Cyclocephala spp.) and seed corn maggot (Delia platura). The use of systemic insecticide seed treatments was still in its infancy, with the introduction of disulfoton in cotton for protection against thrips, followed shortly by the introduction of acephate. Of all these products, only acephate maintains a US Environmental Protection Agency (EPA) registration for seed treatment and its use is minimal due to the introduction of products with greater efficacy. The most significant impact in seed treatment insecticides and seed treatment chemistry in general has come with the development and introduction of the neonicotinoids (clothianidin, imidacloprid and thiamethoxam). The registration by EPA of this class of chemistry for seed treatment use in 1994 provided for the first time the ability to obtain excellent protection with a seed treatment against a wide range of soil-borne insects (e.g., wireworms, grubs, seed corn maggot, grape colaspis (Colaspis brunnea), corn rootworm (Diabrotica spp.)), as well as early season sucking/chewing insects (e.g., thrips, aphids, chinch bug (Blissus spp.), cutworm (Agrotis, Amathes, Peridroma and Prodenia spp.), flea beetle, leafhoppers). This class of chemistry has become the standard for control of early season pests in canola, corn, cotton, onion, rice, sorghum, sugar beets, sweet corn and wheat. The neonicotinoid class of chemistry is having a major impact on agriculture and has been widely accepted by growers because of its many benefits.