biology

Mildew

Mildew is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mildew rather than just read about it. In short: Mildew is a coating of fungal or oomycete growth on plants or other surfaces. It is distinguished from the closely related mould largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white.

Key takeaways

Mildew belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mildew to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mildew from memory before moving on to harder problems.

Reference excerpt

Mildew is a coating of fungal or oomycete growth on plants or other surfaces. It is distinguished from the closely related mould largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consisting of minute hyphae (fungal filaments) produced especially on living plants or organic matter such as wood, paper or leather. Both mould and mildew produce distinct offensive odours, and both are the cause of human ailments. In nature, 'mildew' can refer to either powdery mildews, species of fungus in the family Erysiphaceae, or downy mildews, fungus-like organisms in the family Peronosporaceae. It is also used more generally to mean mould growth. In Old English, mildew meant honeydew (a substance secreted by aphids on leaves, formerly thought to distill from the air like dew), and later came to mean mould or fungus.

Household varieties

The term mildew is often used generically to refer to mould growth, usually with a flat growth habit. Moulds can thrive on many organic materials, including clothing, leather, paper, and the ceilings, walls and floors of homes or offices with poor moisture control. As with moulds, mildew can be cleaned using a mild detergent and water. While some sources recommend a specialised mildew remover, or substances such as bleach (though they may discolour the surface), this is not needed.

There are many species of mould. Common mould genera that grow in buildings include Cladosporium, Stachybotrys, Penicillium, or Aspergillus. Colour alone is not always a reliable indicator of the species of mould. Proper identification requires a microbiologist or mycologist. Mould may appear to grow on non-cellulosic surfaces but are actually growing on the biofilm that adheres to these surfaces. Glass, plastic, and concrete provide no food for organic growth and as such cannot support mould or mildew growth alone without biofilm present. In places with stagnant air, such as basements, moulds can produce a strong musty odour. The pink "mildew" often found on plastic shower curtains and bathroom tile is a red yeast, Rhodotorula.

Environmental conditions Mildew requires certain factors to develop. Without any one of these, it cannot reproduce and grow. The requirements are a food source (any organic material), sufficient ambient moisture (a relative humidity of 62–93%), and reasonable warmth (77–88 °F or 25–31 °C) is optimal. Still, some growth can occur anywhere between freezing and 95 °F (35 °C). Slightly acidic conditions are also preferred. At warmer temperatures, air can hold a greater volume of water; as air temperatures drop, so does the ability of air to hold moisture, which then tends to condense on cool surfaces. This can work to bring moisture onto surfaces where mildew is then likely to grow (such as an exterior wall). Preventing the growth of mildew therefore requires a balance between moisture and temperature. This can be achieved by minimising the moisture available in the air. Air temperatures at or below 70 °F (21 °C) will inhibit growth, but only if the relative humidity is low enough to prevent water condensation (i.e., the dew point is not reached). With warmer temperatures, the water holding capacity of the air increases. This means that if the amount of water vapour in the warming air remains the same, water on solid surfaces or bulk material will tend to evaporate away, drying the material. This again inhibits fungal growth. However, warm, growth-favouring temperatures coupled with high relative humidity will support mildew growth. Air conditioners are one effective tool for removing moisture and heat from otherwise humid warm air. The coils of an air conditioner cause moisture in the air to condense on them, eventually losing this excess moisture through a drain and placing it back into the environment. They can also inhibit mildew growth by lowering indoor temperatures. For them to be effective, air conditioners must recirculate the existing indoor air and not be exposed to warm, humid outside air. Some energy efficient air conditioners may cool a room so quickly that they do not have an opportunity to also effectively collect and drain significant ambient water vapour.

Illustrations

Worked examples

Example 1 — a first encounter with Mildew

Start with the simplest possible case. Write down what Mildew claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mildew before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mildew ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mildew

In research: Mildew appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mildew in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mildew is common in secondary-school and first-year university syllabi. It links to neighbouring topics Building defects, Fungus common names, Plant pathogens and diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Mildew outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Mildew in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mildew means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mildew out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mildew in simple terms?

Why does Mildew matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mildew?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mildew.