Mildew Mistakes: Mold in buildings is Often Mistaken for Mildew
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Does mildew grow in buildings? What mistakes to people make in confusing mildew with mold on building surfaces?
What does mildew look like? What color is mildew?
Photographs of light colored mold & other molds of various colors and textures in buildings - stuff that is mistaken for "mildew"
Questions & answers about mildew and mildew odors in buildings and on building surfaces - is it really mildew? Probably not.
This article discusses how to recognize building mold and how to know that indoors, it's not mildew: This article describes building mold (black mold, green mold, yellow mold, gray mold, and white mold) that is often mistaken for mildew.
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Photographs of Mold Found on or In buildings, Building Contents, Clothing, Baskets, & Artworks: Molds that are Sometimes Mistaken for Mildew
Our photo (left) of white mold on a leather jacket illustrates a fungus that might be mistakenly called "mildew".
Here are photographs of mold on building exteriors, interiors, or building contents. At this website, other photos of mold on indoor building surfaces may help you recognize
mold in buildings, recognize probably-cosmetic mold, and recognize stuff that is not mold and does not need to be tested.Often an inexperienced mold inspector or consumer may refer to these molds incorrectly as "mildew". There are mold genera or species that can grow on a remarkably wide range of organic materials that are found both outdoors and inside, and that can appear in an wide range of colors (black, brown, red, green, gray, white, orange, tan, yellow, for example) and textures.
As we discuss in this article series, mildew, a sub-class of molds, is an obligate parasite that grows only on living plants, and is generally white in appearance. Our page top photograph a severe basement mold contamination in a flooded home found in Poughkeepsie, New York. More photographs of mold that is often mistaken for or mis-named "mildew" are included in this article and links provide articles that correctly identify mildew as well as explain the difference between mildew and mold.
See MOLD APPEARANCE - WHAT MOLD LOOKS LIKE for a photo-guide to indoor molds - real mold or fungal growth in buildings. None of these will be mildew - a plant mold that is an obligate parasite - mildew only grows on living plants.In general, mold is a term encompassing a very wide family of organisms (the Fifth Kingdom) that includes more than a million and a half species. Lots of molds grow on lots of different organic substances, under a variety of conditions of light and temperature, but all molds require moisture and something organic on which to grow (paper, wood, paint, cloth, leather, plastic, etc.).
Carpet mildew diagnosis: carpeting that has light mold or smells like mold might be described by an inexperienced inspector or a building owner as mildewed carpeting. If your carpeting smells like "mildew" or "mold" it 's probably moldy whether you can see the mold or not by simple visual inspection. See CARPET MOLD CONTAMINATION for details.
Our photo of moldy carpet (left) was taken from a sample of carpeting that was the final target of a building mildew odor diagnosis procedure.
Carpet stains: can also be caused by a wide range of sources, some of which are harmless, others may diagnose other building problems such as a heating system that is not working properly, or building air leaks. See CARPET STAIN DIAGNOSIS.
Mold on works of art: We define "mildew" stains on or in paint at Mildew in paint. In support of museum conservators we have also identified mold growth on as well as in paint in works of art. Mildew is not found on art works.
Our photograph of a painting being examined for contaminants was provided courtesy of museum conservator Ulrik Runeberg, Puerto Rico Art Museum during a joint forensic investigation.
Mold on painted building surfaces or furnishings: We define "mildew" stains on or in paint at Mildew in paint. Look closely at our peeling paint photograph at above left and you can see some black mold on the back surface of an old layer of exterior paint exposed by our peel-back of blistered paint on a wood clapboard wall. More black mold is visible on the exposed wood surface too.
Our micro-photograph of a cross-section cut moldy paint (below right) shows black mold growth inside the layer of paint sampled from a surface. It's mold, not mildew. Our high-resolution microscope photograph (below) of mold found on exterior wall paint confirms that this is a mitosporic fungi, not mildew.
A closeup microscopic photo of mold found on building wall paint is shown at left.
Our high-resolution microscope photograph (left) of mold found on exterior wall paint confirms that this is a mitosporic fungi, not mildew.
Mold or algae on roofs: We discuss stains mistaken for mildew on building roofs at Catalog of Black Roof Stains.
Mold on a Leather Jacket or on Clothing
In our forensic lab we confirmed that this "mildewed" leather jacket was actually contaminated with Aspergillus versicolor - it was moldy, not mildewed even though the owner naturally used that term to describe the odor.
Clothing that smells like "mildew" is moldy and can usually be restored by laundering or dry-cleaning. Leather garments need to be cleaned by a leather cleaning professional.
Mold on a Woven Laundry Basket
This "mildewed" laundry basket found in Mexico was mold-contaminated but although the basket was made of plant material, this black mold was not mildew. (Samples are on hand for further laboratory analysis.)
Interestingly the mold grew only on the basket fiber interior surfaces - a side of the plant material that was exposed after the basket reed material was first hand-split for weaving. The harder exterior surface of this bamboo-like plant material did not show much mold growth.
Even using bleach solution (plastic bowl at upper left) we were unable to successfully clean this moldy laundry basket - it was passed on to the trash truck along with other building basura.
This green "mildew" on basement surfaces was confirmed to be mostly Aspergillus sp. mold.
The white, gray, and green "mildew" found on the underside of this building subflooring and on the floor joists was confirmed in our forensic laboratory as not "basement mildew" but rather a mixture of mostly Aspergillus sp. and some Penicillium sp. molds.
We also often find Trichoderma sp. (another green mold) on wooden subfloors and framing over wet or damp basements or crawl spaces.
Green and gray molds on building surfaces are often mistaken for mildew.
White mold in buildings that is not mildew is very common, found for example on wood surfaces, both painted and raw wood. Our photograph (left) shows white mold on an interior basement door.
Often we find white or light gray Aspergillus sp. or Penicillium sp. molds on these surfaces, but there are numerous other light colored or white indoor molds that may be present.
Other examples of white mold found in buildings that is often mistakenly called "mildew" can be seen at White Mold.
White stuff that is not mold is also not mildew: Beware: many people mistake mineral salts or efflorescence for white mold or mildew.
Efflorescence is a white crystalline salt left on masonry surfaces where water or moisture have been evaporating.
See STUFF THAT IS NOT MOLD for photos of white fluffy material or white crystalline material that is often mistaken for mold.
Questions & Answers regarding this article
Questions & answers about mildew and mildew odors in buildings and on building surfaces - is it really mildew? Probably not.
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Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English)
"Identification of two powdery mildew fungi, Oidium neolycopersici sp. nov. and O. lycopersici, infecting tomato in different parts of the world",
Levente KISS, Roger T. A. COOK, Gregory S. SAENZ, James H. CUNNINGTON, Susumu TAKAMATSU, Ian PASCOE, Marc BARDIN, Philippe C. NICOT, Y. SATO and Amy Y. ROSSMAN, Mycological Research (2001), 105:6:684-697 Cambridge University Press, The British Mycological Society 2001 provides an example of the problem of mildew damage to crops, from which we quote the abstract: A world-wide study of the Oidium species causing economic damage on tomato has identified two taxa using classical morphological, scanning electron microscope (SEM) and molecular phylogenetic analyses. The material consisted of a total of 25 tomato powdery mildew isolates and 29 herbarium specimens coming from all continents where tomatoes are grown. A taxon with non-catenate conidia widespread in Europe, Africa, North and South America and Asia was identified as an O. subgen. Pseudoidium species (teleomorph: Erysiphe sect. Erysiphe). Formerly mistaken for O. lycopersicum (or O. lycopersici), it is now recognised as a distinct species, O. neolycopersici sp. nov. A phylogenetic analysis of the internal transcribed spacer (ITS) sequences of the ribosomal DNA (rDNA) indicated that O. neolycopersici is closely related to Erysiphe macleayae, E. aquilegiae and other Pseudoidium species. Only a taxon with catenate conidia was found on Australian specimens. This was identified as a species of O. subgen. Reticuloidium (teleomorph: Golovinomyces sp.). Phylogenetic analysis of the rDNA ITS sequences showed that this species is closely related to O. longipes infecting eggplant. Because it is most likely to be the same species as the original O. lycopersicum, which was actually first described in Australia, this is here neotypified as O. lycopersici.
"Greenhouse Flower Crop Disease Prevention," USDA, originally from the Cornell University Extension, see www.reeis.usda.gov/web/crisprojectpages/209797.html Abstract is quoted in part just below: Greenhouse flower growers are annually faced with the need to manage new diseases caused by powdery mildews and downy mildews that disfigure crops and make them unsaleable. Information is not available to help them determine the source of the epidemics, to control the environment so it is not conducive to disease, to identify less-susceptible crops, or to use the most environmentally responsible chemical protectants.
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
"Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm Below we provide a partial quote from the introduction to this excellent document: Powdery mildew, Leveillula taurica, became a new and serious threat to British Columbia’s greenhouse bell pepper industry early February, 2003. The disease was found simultaneously in two separate locations near Langley in southern British Columbia. Trace amounts of mildew developed on the foliage of cultivar Zamboni in one operation and 10-80% of the foliage of cultivar Triple Four in an organic operation. Reported pepper fruit yield losses have been 2 to 4 kg/m2. By summer, pepper powdery mildew was reported throughout British Columbia’s pepper greenhouses. Dutch research has shown a direct relationship between per cent mildew infection of the leaves and yield loss. One per cent mildew infection on the leaves results in a one percent yield loss. Studies show that the higher the level of powdery mildew infection the higher the loss of production. An early, heavy infection with mildew had about 30% loss of production compared to a later, lighter infection. Powdery mildew generally has caused 10-15% yield loss in NA greenhouse pepper crops. Greenhouse pepper growers need to follow an intensive disease prevention plan because it is very important that powdery mildew never gets out of hand. Once pepper leaves are infected with powdery mildew it is difficult to control; if left unchecked the crop can be entirely destroyed. Monitor the crop right from the start. Apply preventive fungicide sprays once the disease is detected. Carry out strict hygiene throughout the year and practice a thorough year-end clean up. There are no powdery mildew resistant pepper varieties currently available.
Also see:
First report of powdery mildew of greenhouse pepper caused by Leveillula taurica in British Columbia, Canada. Cerkauskas, R.F. and A. Buonassisi. Plant Disease 87: 1151. 2003.
First report of powdery mildew of greenhouse pepper caused by Leveillula taurica in Canada. Cerkauskas, R.F. and J. Brown. Plant Disease 83:781. 1999.
Suppression of powdery mildew on greenhouse-grown cucumber by addition of silicon to hydroponic nutrient solution is inhibited at high temperature. Schuerger, Andrew and W. Hammer. Plant Disease 87:177-185. 2003.
Thanks to reader Debra H. for discussing this topic and whose questions suggested this clarifying article 11/28/2009
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
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