Mauget ArborfosThis product has no expiration date. (active ingredient: Phosphorous acid 45. 8%) SIGNAL WORD: CAUTION USAGE: Arborfos is a phosphite formulated fungicide that inhibits fungal growth through stimulation of the plants own natural defense systems. Research indicates that Arborfos may also elicit a type of systemic acquired resistance response. Although it imparts no actual phosphorous nutrition, Arborfos treated trees tend to develop healthier leaves,