Topsin

Topsin is a brand name for a systemic fungicide used in agriculture and horticulture. The active ingredient in many Topsin formulations is thiophanate-methyl, a benzimidazole carbamate. Thiophanate-methyl is a pro-fungicide that is hydrolyzed in plant tissue to the active metabolite carbendazim, which inhibits fungal cell division by interfering with tubulin polymerization.

Topsin provides systemic protection, moving within the plant to protect new growth after application. It is used to prevent and control diseases caused by fungi such as Botrytis spp., Sclerotinia, and some powdery mildews on a range of crops including fruits (apples, grapes, berries), vegetables, and ornamentals. It is distributed in various formulations, commonly as wettable powder, flowable concentrates, and soluble liquids, and is applied as a foliar spray, soil drench, or, in some crops, trunk treatment, following label directions.

Regulatory status and safety: Because thiophanate-methyl can yield carbendazim residues, regulatory approval for Topsin and its uses varies by country; some crops or regions restrict or prohibit certain applications. As with other pesticides, handling should follow label instructions, use protective gear, and observe pre-harvest intervals and re-entry times. Environmentally, the product can affect aquatic organisms; runoff should be minimized.