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Reason® is a broad-spectrum foliar fungicide that provides effective control of a variety of plant diseases with limited plant-back restrictions for greater in-field flexibility. As a locally systemic foliar fungicide, Reason stops disease development at many stages in the disease life cycle. The active ingredient provides a fast-acting, consistently high level of control. This activity, combined with a strong spore-killing effect, provides complete disease protection for use in bulb vegetables, carrots, cucurbits, fruiting vegetables, grapes, leafy and brassica vegetables, and potatoes.

EPA Reg. No. 10163-371. Always follow and read label instructions. 


  • Fast-acting – Reason® exhibits excellent activity on key stages within the pathogen life cycle sites of action. Acts rapidly against both the direct and indirect germination cycles of the disease, resulting in consistent and effective disease prevention.
  • Translaminar Movement – Penetrates and moves through the leaf tissue to protect the untreated side of the leaf. This movement prevents the progression of diseases, as well as pathogen sporulation on both sides of the leaf.
  • Strong Anti-sporulation Activity – Prevents sporulation, effectively stopping pathogens before they can spread to healthy leaf tissue and other plants within the field.
  • Curative and Protective Performance - Reason exhibits curative properties under certain conditions, which can be a relief during a tough season. Though Reason exhibits curative properties, Gowan recommends early application for best results. Reason is especially active on oomycete diseases. Studies have shown that once applied to leaf buds, it stays within the plant and protects the new and expanding leaves.

Key Diseases Controlled

• Alternaria leaf spot

• Black dot (suppression)

• Downy mildew

• Early blight

• Late blight

• Purple blotch

• White rust

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