Technical Abstract: Pecan growers have a good selection of fungicides to use for disease control. However, within the past year there has been increasing attention given to another class of fungicide for disease control on pecans. There are over a dozen products that contain phosphite (phosphorous acid) as the active ingredient. The situation is confused by the fact that these products are labeled for use not only as fungicides, but also as fertilizers and even biostimulants. The labels are very broadly written to cover a wide range of crops and diseases, some of which have little or no actual field use data, and the situation for pecan is confused. The article describes what phosphites are, and whether they are useful on pecans. Phosphorous acid (H3PO3) disassociates to release dihydrogen phosphite (H2PO3-) and hydrogen phosphite (HPO32-), which are also readily taken up by plants. Although there are some reports suggesting nutritional benefits from phosphites, the bulk of scientific studies show that this is not the case. However, they have clearly been shown to be fungicides omnn many crops, particularly against oomycete pathogens. They have not been evaluated on pecan for control of pecan disease, but trials are underway at various sites in GA to test this poromising range of compounds.