User:Hotlunch2000

Over the past 35 years or so, phosphite has been widely used to improve the yield of many crops throughout world. Phosphite’s use is controversial as it is being widely marketed both as a crop fungicide and as a superior source of crop phosphorus nutrition (i.e. P fertilizer). At least 10 different agrochemical companies in Europe and North America appear to have avoided the substantial cost and time associated with registering a fungicide by labeling their phosphite product as a P-fertilizer. It is well established that fungicides based on phosphite are an effective control agent for crop pathogens belonging to the order Oomycetes (esp. Phytophthora sp). However, no evidence exists that plants can use phosphite as their sole source of nutritional P. Although plants readily absorb and translocate phosphite, it is quite stable in planta and is not readily metabolized. Phosphite rapidly kills phosphate-starved plants as it represses plant genes that are specifically induced during phosphate starvation (to help plants survive phosphate deprivation), as well as plant morphological responses to Pi stress (such as an increased root:shoot growth ratio). This research seriously compromises the credibility of the many companies that market phosphite as a ‘super P-fertilizer’rather than as a fungicide.

All of this is summarized in a recent review article about phophite that was written by Thao & Yamakawa (2008) and published in Soil Science and Plant Nutrition, vol 55: pp. 228-234