{"id":4613,"date":"2011-03-21T09:33:07","date_gmt":"2011-03-21T13:33:07","guid":{"rendered":"http:\/\/extension.umaine.edu\/ipm\/"},"modified":"2021-08-31T16:16:48","modified_gmt":"2021-08-31T20:16:48","slug":"5085e","status":"publish","type":"page","link":"https:\/\/extension.umaine.edu\/ipm\/ipddl\/publications\/5085e\/","title":{"rendered":"Powdery Mildew of Cucurbits"},"content":{"rendered":"

\n \n \"Print\n <\/a>\n <\/div><\/h3>\n

Pest Management Fact Sheet #5085<\/h3>\n

For information about UMaine Extension programs and resources, visit extension.umaine.edu<\/a>.
\nFind more of our publications and books at extension.umaine.edu\/publications\/<\/a>.<\/strong>
\n<\/span><\/strong><\/p>\n

Introduction<\/h3>\n

Powdery mildew of cucurbits is caused by either of two fungi. Sphaerotheca fuliginea<\/em> (less common) is known to infect about 60 plant genera and Erysiphe cichoracearum<\/em> is known to infect about 160 plant genera. All cucurbits are susceptible to powdery mildew although it does not commonly attack watermelon. Yield losses of up to 50% have been reported and are the result of defoliation caused by the fungi.<\/p>\n

Environmental Conditions<\/h3>\n

Unlike most fungi, the spores of powdery mildew do not require free water for germination and are actually inhibited in its presence. High humidity is beneficial but not necessary for spore germination. Infection has been known to occur below a relative humidity of 50%, although the humidity at the surface of the leaf is undoubtedly higher. High humidity also increases the rate at which the fungus grows after infection occurs. Spores will germinate above 50\u00b0F with an optimum of around 80\u00b0F and an upper limit of 90\u00b0F.<\/p>\n

Symptoms<\/h3>\n

The initial signs of the fungus show on the upper or lower surface of (especially) shaded leaves. The infection may appear first as a pale yellow spots but the fungus soon sporulates yielding a characteristic powdery-white appearance (brown in the case of Sphaerotheca<\/em>). This powdery appearance can involve the entire leaf which eventually turns yellow then brown and dries to the point that it crumbles when crushed.<\/p>\n

Survival and Dispersal<\/h3>\n

Overwintering of the fungi probably does not occur in Maine, although survival is possible on alternate hosts in the greenhouse. The initial infections are from spores carried by the wind from more southerly areas. Once the disease is present in the crop, abundant numbers of spores are produced which can spread the disease quite rapidly. Tens of millions of spores can be produced on a single infected leaf.<\/p>\n

Control<\/h3>\n
    \n
  1. Use resistant varieties.<\/li>\n
  2. Plant in areas with good air drainage and allow for maximum air circulation.<\/li>\n
  3. Crop rotation and fall plowing are of no benefit because the fungus does not survive in the field.<\/li>\n
  4. The fungicides listed in the tables below are registered for powdery mildew control.<\/li>\n<\/ol>\n\n\n\n\n\n\n\n
    \n

    Traditional Fungicides for Powdery Mildew Control<\/strong><\/h4>\n<\/caption>\n

    Fungicide<\/strong><\/th>\nApply when first observed<\/strong><\/th>\nExamples of Trade Names<\/strong><\/th>\n<\/tr>\n<\/thead>\n
    Strobilurins: azoxystrobin trifloxystrobin<\/td>\nAlternate with other chemicals. 5-7 day schedule<\/td>\nQuadris, Flint<\/td>\n<\/tr>\n
    chlorothalonil<\/td>\nGood coverage is critical. 7 day schedule<\/td>\nDaconil, Bravo, Echo, Fungonil and others<\/td>\n<\/tr>\n
    myclobutanil<\/td>\nAlternate with other chemicals<\/td>\nNova<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

     <\/p>\n\n\n\n\n\n\n\n\n\n\n
    \n

    Alternative Fungicides for Powdery Mildew Control<\/strong><\/h4>\n<\/caption>\n

    Fungicide<\/strong><\/th>\nApply when first observed<\/strong><\/th>\nExamples of Trade Names<\/strong><\/th>\n<\/tr>\n<\/thead>\n
    Bacillus subtilis<\/em> strain QST 713<\/td>\nCoverage critical. Preventative 7 day schedule.<\/td>\nSerenade<\/td>\n<\/tr>\n
    copper products<\/td>\nCoverage critical. 5-7 day schedule.<\/td>\nKocide, Tenn-Cop, Basicop, and others<\/td>\n<\/tr>\n
    Neem oil<\/td>\nPreventative 7-14 day schedule.<\/td>\n70% Neem Oil<\/td>\n<\/tr>\n
    Potassium bicarbonate<\/td>\n7-14 day schedule.<\/td>\nRemedy Fungicide, Armicarb 100<\/td>\n<\/tr>\n
    Potassium salt of fatty acids<\/td>\n7-10 day schedule.<\/td>\nM-pede<\/td>\n<\/tr>\n
    sulfur<\/td>\nCoverage critical. 5-7 day schedule.<\/td>\nSulfur Dust, Wettable Sulfur, and others<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
    \n

    When Using Pesticides<\/strong><\/span><\/p>\n

    ALWAYS FOLLOW LABEL DIRECTIONS!<\/strong><\/span><\/h3>\n

    Pest Management Unit
    \nCooperative Extension Diagnostic and Research Laboratory
    \n17 Godfrey Drive, Orono, ME 04473-1295
    \n1.800.287.0279 (in Maine)<\/p>\n

    \n

    Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.<\/em><\/p>\n

    \u00a9 2010<\/p>\n

    Call 800.287.0274 (in Maine), or 207.581.3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit extension.umaine.edu<\/a>.<\/strong><\/p>\n

    The University of Maine is an EEO\/AA employer, and does not discriminate on the grounds of race, color, religion, sex, sexual orientation, transgender status, gender expression, national origin, citizenship status, age, disability, genetic information or veteran\u2019s status in employment, education, and all other programs and activities. The following person has been designated to handle inquiries regarding non-discrimination policies: Sarah E. Harebo, Director of Equal Opportunity, 101 North Stevens Hall, University of Maine, Orono, ME 04469-5754, 207.581.1226, TTY 711 (Maine Relay System).<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

    Pest Management Fact Sheet #5085 For information about UMaine Extension programs and resources, visit extension.umaine.edu. Find more of our publications and books at extension.umaine.edu\/publications\/. Introduction Powdery mildew of cucurbits is caused by either of two fungi. Sphaerotheca fuliginea (less common) is known to infect about 60 plant genera and Erysiphe cichoracearum is known to infect […]<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":3249,"menu_order":43,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-4613","page","type-page","status-publish","hentry"],"yoast_head":"\nPowdery Mildew of Cucurbits - Cooperative Extension: Insect Pests, Ticks and Plant Diseases - University of Maine Cooperative Extension<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/extension.umaine.edu\/ipm\/ipddl\/publications\/5085e\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Powdery Mildew of Cucurbits - Cooperative Extension: Insect Pests, Ticks and Plant Diseases - University of Maine Cooperative Extension\" \/>\n<meta property=\"og:description\" content=\"Pest Management Fact Sheet #5085 For information about UMaine Extension programs and resources, visit extension.umaine.edu. 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