{"id":920,"date":"2020-03-26T16:11:38","date_gmt":"2020-03-26T20:11:38","guid":{"rendered":"https:\/\/site.extension.uga.edu\/worthag\/?p=920"},"modified":"2020-03-26T16:13:41","modified_gmt":"2020-03-26T20:13:41","slug":"pecans-clarification-on-phosphite-materials","status":"publish","type":"post","link":"https:\/\/site.extension.uga.edu\/worthag\/2020\/03\/pecans-clarification-on-phosphite-materials\/","title":{"rendered":"Pecans – Clarification on Phosphite Materials"},"content":{"rendered":"\n

As pecans are breaking bud, many growers are beginning fungicide spray programs. Following is information from Dr. Lenny Wells, UGA Pecan Specialist, to help answer questions and explain more about Phosphite materials.<\/strong><\/p>\n\n\n\n

Based on conversations I have had with a number of growers it sounds \nas if there is a need for some clarification regarding phosphite \nmaterials. Phosphite has become a very valuable tool for us in the \nbattle against pecan scab. Dr. Tim Brenneman first began testing \nphosphite materials on pecan primarily for efficacy on some of our minor\n foliar diseases like anthracnose a number of years ago (since at least \n2009). <\/p>\n\n\n\n

In the course of Dr. Brenneman\u2019s research he began to notice that \nphosphite also had a significant effect on scab\u2014especially leaf scab. As\n his research continued, he developed a large data set on phosphite over\n several years, using many different phosphite products. UGA Extension \nrecommendations for phosphite use are based solely<\/em><\/strong>\n on Dr. Brenneman\u2019s research. Initially it was only recommended for use \nin combination with other products, never as a stand-alone. Dr. \nBrenneman now has the data to show that at rates of at least 2 qts per \nacre, phosphite can be used alone for leaf scab during the \npre-pollination stage. It is an excellent leaf scab material and this is\n where its best use lies. It can be used during nut sizing as well but \nin high scab pressure situations, should be tank mixed with another \nfungicide for nut scab.<\/p>\n\n\n\n

Now, what exactly is phosphite? Phosphite (H3 PO3 ) is derived from Phosphorous acid<\/strong>, NOT Phosphoric acid<\/strong>\n (H3PO4) which is a fertilizer. Phosphorous acid dissociates to form \nthe phosphonate ion (HPO3 2-), also called phosphite. Phosphites are \nhighly systemic and very stable in plants. There is evidence that \nphosphite may stimulate host defenses . <\/p>\n\n\n\n

Phosphite or Phosphorous acid is not converted into phosphate, which is the primary nutrient source of P for plant <\/strong><\/em>.\n There are bacteria capable of transforming phosphite into phosphate, \nbut this process is so slow that it is of no practical relevance. To \ndate, no plant enzymes are known to convert phosphite into phosphate. \nTherefore, any claims that phosphite can contribute to P nutrient \nrequirements for plant growth should be taken with much caution. <\/p>\n\n\n\n

As a matter of fact, phosphite can trick plants into thinking they \nhave enough P, which may potentially contribute to P deficiency when \nphosphite is over-used (see the article linked here for more info on this topic)<\/a>. <\/p>\n\n\n\n

There is apparently some concern out there about the salts present in\n many phosphite products. If purity of product is of specific concern to\n you, then you should use a phosphite product that does not have salts \npresent (bear in mind, that your soil applied potash [KCl] is also a \nchloride containing salt). However, Dr. Brenneman\u2019s research\n has shown no negative effect from phosphite products containing salt in\n his research going back at least 10-11 years.<\/em><\/strong> There is no evidence for greater toxicity risk in phosphite products containing salt than for those without salt.<\/p>\n\n\n\n

If you are concerned about the long term effects of products \ncontaining salt, you may also want to consider the fact that phosphite \nitself is not metabolized by the plant and we also do not know what the \nlong-term ramifications of that may be. Let me be clear, we do not have \nany evidence that would lead us to believe this will cause any \ndetrimental effects to pecan trees. Nor do we have any evidence to \nsuggest the salts present in some phosphite products will cause any \ndetrimental effects. If independent research on either topic leads to \nmore information on this, we will let you know.<\/p>\n\n\n\n

In short, Dr. Brenneman\u2019s research trials have shown that as far as efficacy is concerned, all the phosphite products Dr. Brenneman has tested (<\/em><\/strong>which include most of those we currently use in pecan\u2014I won\u2019t list them because there are too many to be named) work equally well on pecan scab<\/em><\/strong> and the other minor diseases from which phosphite provides protection and there is no more risk of toxicity with one phosphite product than there is with another. <\/em><\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

As pecans are breaking bud, many growers are beginning fungicide spray programs. Following is information from Dr. Lenny Wells, UGA Pecan Specialist, to help answer questions and explain more about Phosphite materials. Based on conversations I have had with a number of growers it sounds as if there is a need for some clarification regarding […]<\/p>\n","protected":false},"author":276,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20,6],"tags":[],"class_list":["post-920","post","type-post","status-publish","format-standard","hentry","category-pecan","category-plant-pathology"],"_links":{"self":[{"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/posts\/920","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/users\/276"}],"replies":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/comments?post=920"}],"version-history":[{"count":2,"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/posts\/920\/revisions"}],"predecessor-version":[{"id":922,"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/posts\/920\/revisions\/922"}],"wp:attachment":[{"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/media?parent=920"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/categories?post=920"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/worthag\/wp-json\/wp\/v2\/tags?post=920"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}