Using Copper in the Garden: Fungicide, Bactericide, and Slug Control

Copper compounds serve as fungicides/bactericides, and copper barriers offer safe, non-toxic slug/snail control—ideal for organic gardening.

How Copper Works

Copper ions destroy proteins in fungi/bacteria. In high concentrations this harms plants, but careful application makes copper effective against blights, fungal issues, and bacterial diseases. Mid-1800s discovery: copper sulfate + lime (Bordeaux mixture) controlled downy mildew on grapes. Modern formulations use less soluble, fixed copper for even safer crop use.

Copper repels slugs/snails—contact with their slime creates an electric-shock-like reaction disrupting their nervous system.

Copper Forms for Slug Control

Physical Barriers (Best): Copper tape, foil, screens erected vertically around beds/containers. Only protect slug-free areas (including eggs). Solarize with black plastic first to eliminate existing pests. Screens must extend 2+ inches below soil to prevent burrowing; minimum 4-inch width. Band tree trunks with foil/tape, leaving gaps at ends, tightening annually for growth. Clean tarnished copper with vinegar solution.

Bordeaux Mixture: Copper sulfate + lime brushed on woody stems/trunks (4-6 inches above soil). Add white latex paint for longer adhesion. Pre-mixed solutions recommended.

Physical barriers provide lasting, non-toxic control without risk of liquid formula misapplication.