Fluopyram is a synthetic chemical widely used in modern agriculture as a broad-spectrum pesticide that acts as both a fungicide and a nematicide. Introduced commercially in the early 2010s, this active ingredient protects high-value crops globally against a variety of destructive pathogens. It provides growers with a tool for managing both above-ground fungal diseases and below-ground parasitic nematodes. The compound is applied to fields, orchards, and vineyards to prevent significant yield losses.
The Mechanism of Action
Fluopyram functions by interfering with the fundamental process of energy generation within the target organisms, placing it in the chemical group known as Succinate Dehydrogenase Inhibitors (SDHIs). This chemical class disrupts the cellular respiration of fungi and nematodes, which is necessary for their growth and survival. Fluopyram specifically binds to and inhibits the enzyme succinate dehydrogenase (SDH), also identified as Complex II in the mitochondrial electron transport chain.
SDH catalyzes the conversion of succinate to fumarate, a step that is a part of both the Krebs cycle and the electron transport chain. By inhibiting this specific step, Fluopyram effectively prevents the transfer of electrons. The disruption halts the production of adenosine triphosphate (ATP), the molecule that provides energy for all cellular activities.
Because the fungus or nematode cannot produce sufficient energy, its growth, spore germination, and mobility are severely curtailed, leading to cell death. This mode of action is systemic, meaning the chemical is absorbed by the plant and moves through its tissues, offering protection from within.
Agricultural Uses and Targeted Pests
Fluopyram is registered for use across a wide array of agricultural crops, including high-value fruits like grapes, apples, and cherries, and vegetables such as potatoes, tomatoes, and cucurbits. Its application extends to field crops like soybeans and cotton, where it is often used as a seed treatment to protect seedlings from early threats. The product is valued for its versatility in controlling numerous fungal diseases.
As a fungicide, it is highly effective against major pathogens.
Targeted Fungal Diseases
- Powdery mildew, which affects the surface of leaves and fruit.
- Botrytis cinerea, the fungus responsible for gray mold in berries and grapes.
- Sclerotinia rot, which causes white mold on various crops.
- Alternaria leaf spot.
Its broad-spectrum activity allows growers to simplify their spray programs by targeting multiple diseases with a single application.
The compound also has a distinct utility as a nematicide, targeting microscopic, soil-dwelling worms that feed on plant roots. Fluopyram is used to suppress plant-parasitic nematodes, including root-knot nematodes (Meloidogyne spp.) and lesion nematodes (Pratylenchus spp.). This dual action helps maintain root health and manage resistance by providing an alternative mode of action when rotated with other chemical classes.
Human Health and Environmental Safety Profile
Fluopyram has undergone extensive toxicological review by regulatory bodies like the U.S. Environmental Protection Agency (EPA) and equivalents in the European Union. Acute toxicity studies have generally classified the chemical as having low toxicity when exposed orally, dermally, or via inhalation. The median lethal dose (LD50) for oral and dermal exposure in rats is over 2,000 milligrams per kilogram of body weight.
Chronic toxicity studies have indicated that long-term exposure can lead to specific health effects, primarily involving the liver and the thyroid gland in laboratory animals. The EPA has classified Fluopyram as “Likely to be Carcinogenic to Humans” based on these chronic animal studies. Regulatory bodies have concluded that the established chronic population adjusted dose is protective of all long-term effects, including potential carcinogenicity, for the general public from dietary exposure.
Environmentally, Fluopyram exhibits moderate mobility in soil, suggesting a potential for leaching, but it also shows a high degree of persistence. Its half-life in soil can range from tens to hundreds of days, with dissipation times (DT50) up to 539 days. This persistence raises concerns about its potential to carry over into subsequent crops or to reach groundwater.
A specific environmental concern relates to its degradation into trifluoroacetic acid (TFA), a persistent chemical that is highly mobile in water. This issue has led certain jurisdictions, such as Denmark, to ban the use of Fluopyram to protect groundwater sources from TFA contamination. Assessments of its impact on non-target species suggest a negligible risk to beneficial insects like honey bees and soil organisms.