{"id":413,"date":"2009-10-19T09:26:58","date_gmt":"2009-10-19T07:26:58","guid":{"rendered":"http:\/\/www.my-grape-vine.com\/blog\/?p=413"},"modified":"2012-09-11T11:35:56","modified_gmt":"2012-09-11T11:35:56","slug":"controlling-powdery-mildew-on-grapes","status":"publish","type":"post","link":"http:\/\/www.my-grape-vine.com\/blog\/controlling-powdery-mildew-on-grapes\/","title":{"rendered":"Controlling Powdery Mildew On Grapes"},"content":{"rendered":"<!-- google_ad_section_start --><p>Powdery mildew is the main fungal disease that most grape growers confront\u00a0every seasons.\u00a0\u00a0 The fungus that cause powdery mildew\u00a0is called\u00a0Uncinula Necator.<\/p>\n<p>Many\u00a0grape growers struggled to keep powdery mildew\u00a0under control in vineyards, as once\u00a0your vines are infected and the symptoms are visible,\u00a0the\u00a0disease\u00a0already is in an advance stage of development.<\/p>\n<p>The symptoms are visible on <span style=\"text-decoration: underline;\"><strong>all<\/strong><\/span> green parts of the grape vine.<\/p>\n<p><strong>On the berries:<\/strong><\/p>\n<p style=\"text-align: left;\">A white powdery substance covers the berries &#8211; it looks like a white dust that can be rubbed off.\u00a0 These &#8220;dust&#8221; particles are the actual spores of the powdery mildew fungus.\u00a0 Infected berries will have what appears to be a net-like pattern when the &#8220;dust&#8221; is rubbed off with your finger.\u00a0 They most probably will\u00a0crack open and dry up.\u00a0 If the infection takes place early and the fungus disease spreads too fast, it can cause total crop loss!<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter\" src=\"http:\/\/bp3.blogger.com\/_0za2BhuSFXo\/RqbU56Lg67I\/AAAAAAAAALw\/u4SwYQvzo0Q\/s320\/hugh.jpg\" alt=\"\" width=\"320\" height=\"240\" \/><\/p>\n<p style=\"text-align: left;\">Berries are extremely susceptible from the immediate pre-bloom stage through fruit set.\u00a0\u00a0This is the most critical time to keep powdery mildew under control.\u00a0\u00a0Severe powdery mildew\u00a0infections on the clusters is usually a result of poor fungus control and canopy management throughout this period.<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone\" src=\"http:\/\/www.my-grape-vine.com\/images\/powdery%20mildew%20cane.jpg\" alt=\"\" width=\"212\" height=\"60\" \/><\/p>\n<p>On the canes (in the dormant season), you can see old infections because they will show up as brown areas. As the fungus grows on the grapes and vines and begins to produce spores you will see that the tissue that is infected with have an ash grey powdery look.<\/p>\n<p>On green shoots, the same powdery &#8220;dust&#8221; will be visible.\u00a0 The fungus will infect the green tissue, and will reduce photosynthesis and overall grape vine vigor.<\/p>\n<p style=\"text-align: left;\"><strong>On the leaves:<\/strong><\/p>\n<p style=\"text-align: left;\">Powdery mildew on the leaves of a grape vine, appear as a white dust on the upper and lower part of the leaves.\u00a0 With severe infections, discoloration and drying out of the leaves are visible.\u00a0 No need to say how bad this is for berry size, sugar development and overall growth of the vine!<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone\" src=\"http:\/\/bp2.blogger.com\/_0za2BhuSFXo\/RqbWAqLg68I\/AAAAAAAAAL4\/IQhB8RMm0wg\/s320\/powdery_mildew.JPG\" alt=\"\" width=\"320\" height=\"240\" \/><\/p>\n<p>I often get emails asking about continuous powdery mildew infections, year after year.\u00a0 There is only one explanation for this &#8211; the fungus spores over-winter on the grape vine and in the following growing season, once the conditions for inoculation is ideal, the infection will start again.\u00a0 As you can imagine, this is a vicious circle, that will give you many headaches!<\/p>\n<p><strong>What is the ideal conditions for the inoculation?<\/strong><\/p>\n<p>For the powdery mildew, fungus to develop and spread there needs to be free water (from rain, over-head irrigation and even high humidity) and heat.\u00a0 Spore cells, or cleistothecia overwinter within cracks in the bark of the vine and when rains of approximately 0.1 inch (10 mm) or more occur in spring, and if temperatures are at least 50 \u00b0F (10\u00b0 C), these spores are released and will infect the nearby leaves, canes and bunches.\u00a0 The higher the temperature, the more spores will be released.\u00a0 The optimum temperature is mid 80s \u00b0 F or mid 20s \u00b0 C and higher is the optimum temperature for high spore release.\u00a0 When the temperature reach the high 90s (+30&#8217;s \u00b0 C), the development or spread of powdery mildew will be restricted.<\/p>\n<p><strong>Controlling Powdery Mildew:<\/strong><\/p>\n<p><span style=\"text-decoration: underline;\">Chemical control:<\/span>\u00a0 With the wide range of fungicides now registered for use on vines, the question arises as to which is best and when is the most appropriate time to apply.\u00a0 Where powdery mildew control is poor this is usually due to inadequate spray\u00a0 coverage or the interval between sprays being too long rather than reduced fungicide\u00a0efficacy.<\/p>\n<p>As said earlier, grape berries are most susceptible to powdery mildew during the period from just before flowering to 4 to 5 weeks after fruit set, and failure to control the disease during this period can result in serious crop loss.\u00a0\u00a0The best control is achieved by applying\u00a0a fungicide with an active ingredient called\u00a0strobilurin or DMI fungicides during this period.<\/p>\n<p><span style=\"text-decoration: underline;\">Organically:<\/span>\u00a0 Controlling Powdery Mildew organically is much harder.\u00a0 The most important point to remember is that moisture and heat is needed for the fungus to spread.<\/p>\n<p>Maintaining <strong>proper airflow and sunlight penetration<\/strong> into the vine will ensure a &#8220;drier&#8221; micro climate inside the vine.\u00a0 Direct contact with sunlight will also kill powdery mildew spores and reduce the chances of crop loss.\u00a0 This can be achieved with good canopy management (suckering, leave pulling, tying of shoots, removing of water shoots etc. (consult the <a rel=\"nofollow\" href=\"http:\/\/www.my-grape-vine.com\/dlg\/sell.php?prodData=cb,11\" target=\"_blank\"><strong>Complete Grape Growing System<\/strong> <\/a>for details, it&#8217;s all there!).<\/p>\n<p>I hope this article will help you solve Powdery Mildew problems on your grapes.<\/p>\n<p><strong><span style=\"color: #ff0000;\">Remember:<\/span><\/strong>\u00a0 Maintain a proper canopy, keep your spray applications up to date and be on the look-out for the symptoms I&#8217;ve shown you.<\/p>\n<p>Take care<\/p>\n<p>Danie (The Grape Guy)<\/p>\n<p><a rel=\"nofollow\" href=\"http:\/\/www.my-grape-vine.com\">www.my-grape-vine.com<\/a><\/p>\n<div><\/div>\n<p>&nbsp;<\/p>\n<h3 style=\"text-align: center;\"><span style=\"text-decoration: underline;\"><span style=\"font-family: Helvetica; color: #000000; font-size: x-small;\"><span style=\"font-family: Arial;\"><span style=\"font-family: Arial;\"><span style=\"font-family: Arial; font-size: small;\"><span style=\"font-family: Lucida Sans Unicode; color: #ff0000;\"><span style=\"font-size: x-small;\"><span style=\"font-size: xx-small;\">Was this helpful.\u00a0 Now learn how to grow your grape vine the correct way.<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span style=\"text-decoration: underline;\"><span style=\"font-family: Helvetica; color: #000000; font-size: x-small;\"><span style=\"font-family: Arial;\"><span style=\"font-family: Arial;\"><span style=\"font-family: Arial; font-size: small;\"><a rel=\"nofollow\" href=\"http:\/\/www.my-grape-vine.com\/dlg\/sell.php?prodData=cb,11\" target=\"_blank\"><span style=\"font-size: x-small;\"><span style=\"font-size: xx-small;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter\" src=\"http:\/\/www.my-grape-vine.com\/images\/getnow.gif\" alt=\"\" width=\"250\" height=\"80\" \/><\/span><\/span><\/a><\/span><\/span><\/span><\/span><\/span><\/h3>\n<p style=\"text-align: center;\">For only $29, you get instant access to all the grape growing information you need, PLUS get some bonus videos of how to prune and train a grape vine.\u00a0 The Complete Grape Growing System is a digital product.\u00a0\u00a0You will not receive any physical products.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<!-- google_ad_section_end -->","protected":false},"excerpt":{"rendered":"<!-- google_ad_section_start --><p>Powdery mildew is the main fungal disease that most grape growers confront\u00a0every seasons.\u00a0\u00a0 The fungus that cause powdery mildew\u00a0is called\u00a0Uncinula Necator. Many\u00a0grape growers struggled to keep powdery mildew\u00a0under control in vineyards, as once\u00a0your vines are infected and the symptoms are visible,\u00a0the\u00a0disease\u00a0already is in an advance stage of development. The symptoms are visible on all green [&hellip;]<\/p>\n<!-- google_ad_section_end -->","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12,1,28,37],"tags":[56],"class_list":["post-413","post","type-post","status-publish","format-standard","hentry","category-grape-diseases","category-grow-grapes","category-how-to-grow-grapes","category-powdery-mildew-on-grapes","tag-how-to-grow-grapes"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.2 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Powdery Mildew On Grapes<\/title>\n<meta name=\"description\" content=\"Powdery Mildew on grapes is one of the main disease problems throughout the world. 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