Did you know that people have used seaweed products in agriculture for hundreds of years? I spray our crops with seaweed extract every week because it keeps my crop healthy and growing strong with very few disease problems. I’m not the only one that thinks this is true. Seaweed components have been used for centuries to improve soil dynamics and enhance growth of agricultural crops. A quick review of the scientific literature reveals several different proposed mechanisms behind the reported disease resistance associated with seaweed extracts. It has been suggested that seaweed extracts may serve as a food source and promote the proliferation of favorable microbes which outcompete or antagonize pathogenic organisms. Direct antagonism of the pathogen by the seaweed extract or the betaines contained in seaweed extracts suppressing disease have also been proposed. In addition it has been demonstrated that antioxidant properties of seaweed extract may suppress diseases. Reports of disease suppression most often hypothesize that plant responses are due to an elicitation of plant defences, possibly by oligo- or polysaccharides, peptides, proteins, lipids, cell wall debris, carrageenans, laminarin, β 1-3 glucans or sulfated fucans or some combination of these substances. It is my personal opinion that the mode of action of seaweed extract in suppressing diseases of plants may be complex and involve several modes of action. No wonder people have used seaweed products on their crops for hundreds of years! I’m hooked.