Diflufenican is a synthetic carboxamide herbicide used in agriculture to control broad-leaved weeds. It helps farmers manage weeds that compete with crops for resources like water, nutrients, and sunlight, supporting healthier crop yields. The herbicide has been used in Europe and Australia since the mid-1980s, with recent registrations in North America for specific crops.
Mechanism of Action
Diflufenican disrupts the biosynthesis of carotenoids in plants. Carotenoids are plant pigments that protect chlorophyll during photosynthesis by absorbing excess light energy. The herbicide inhibits phytoene desaturase, an enzyme crucial for converting colorless phytoene into colored carotenoids; when blocked, phytoene accumulates, and the plant cannot produce these protective pigments. Without them, chlorophyll becomes vulnerable to sunlight damage and breaks down. This leads to a visible “bleaching” effect on new plant tissues, followed by necrosis and eventual death.
Agricultural Uses
Diflufenican is used to control broad-leaved weeds in various agricultural settings. It is commonly applied to cereal crops such as wheat, barley, winter rye, and winter triticale, as well as oilseed rape, lupins, lentils, and field peas. It is effective against broad-leaved weeds including wild radish, wild turnip, chickweed, speedwell, cranesbill, and dead nettles. Application can occur pre-emergence or early post-emergence, typically at rates from 125 to 250 grams per hectare, providing both contact and residual activity for up to 8 weeks after application under favorable conditions. It is often used in combination with other herbicides, such as pendimethalin, flufenacet, or bromoxynil, to broaden weed control and manage herbicide resistance.
Safety and Environmental Impact
Regarding human safety, diflufenican exhibits low acute toxicity through oral, dermal, and inhalation routes; it is minimally irritating to eyes and skin, with no known allergic skin reactions, and dietary intake estimates from food and drinking water are low, indicating minimal health concern for the general population. In terms of environmental fate, diflufenican is highly persistent in soil, breaking down slowly with a half-life of 15 to 30 weeks; despite its persistence, it has low mobility and is not expected to leach into groundwater, though in surface water it can move into sediments where it may persist. Diflufenican is highly toxic to algae and moderately toxic to other aquatic organisms, including invertebrates, fish, and amphibians. To mitigate these risks, regulatory guidelines require spray buffer zones and precautionary statements on product labels to protect non-target terrestrial plants and aquatic habitats. It poses a negligible risk to earthworms, beneficial arthropods, bees, birds, and mammals; while not expected to accumulate significantly in organisms, its environmental persistence requires careful management to minimize potential long-term impacts.