Abstract: Materials comprised of linked, repeat units of beta glucosamine, having a molecular weight in the range of 400 to 10,000 are highly effective in controlling fungus infestation in agricultural crops, both pre-harvest and post-harvest. The antifungal material is preferably combined with a mildly acidic solvent to produce a composition having a slightly acidic, or near neutral pH. When the antifungal material is combined with a chitosan matrix, a synergistic interaction occurs which greatly enhances the effect of the resultant composition. Also disclosed is a method for producing a chitin or chitosan based material which will dissolve in water having a neutral pH.