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Black spot -

Commonly found on roses, black spot is a fungal disease. Found as well on other fruits and flowers, black spot doesn't kill the plant, but weakens it and makes it susceptible to other problems.

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Black spot -

It appears during moist and cool weather as small black spots on foliage, which then turns it yellow and eventually falls down. To avoid this, keep foliage clean and dry by mulching beneath plants.

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Black spot -

Position the plant where morning sun will quickly evaporate dew. Also, water the roots, rather than the foliage. Plants can also be sprayed with fungicide to prevent black spot.

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Damping-off disease -

Usually affecting newly-sown plants, damping-off disease is caused by several soil-borne fungi. It's mostly problematic in wet and humid conditions.

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Damping-off disease -

Damping-off disease infects seedlings and causes them to collapse and decay. Gardeners will often find it in greenhouses, but it can appear outside as well.

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Damping-off disease -

There's no treatment, but it can be prevented by using new pots, cell packs, or trays. When sowing, avoid crowding seedlings and provide adequate ventilation.

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Downy mildew -

Downy mildew is caused by fungus-like organisms that often occur during wet weather. It affects many ornamentals and edibles, such as impatiens, pansies, lettuce, and broccoli.

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Downy mildew -

The upper portion of plants become discolored, while the bottoms develop white or gray mold. Unfortunately, no fungicides are available, but some practices can help.

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Downy mildew -

Remove and destroy infected leaves, or the entire plants, if infected. Avoid crowding or watering them in the evening, and rotate edibles year to year.

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Fusarium wilt -

Caused by a soil-borne fungus, fusarium wilt affects ornamental and edible plants, such as tomatoes, peas, and asparagus.

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Fusarium wilt -

It causes wilted leaves, stunted plants, root rot, and sometimes blackened stem rot. It commonly occurs in hot summer temperatures.

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Fusarium wilt -

There are no chemical controls for home gardeners, so if it shows up somewhere in the garden, remove and destroy infected plants. Also, not that you can't plant the same species in the same spot for five years.

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Mosaic virus -

There are several types of mosaic viruses, but the most common ones are tomato mosaic virus and tobacco mosaic virus. The first infects tomatoes, potatoes, peppers, apples, pears, and cherries. And the second one also infects tomatoes and peppers, as well as cucumbers, lettuce, beets, petunias, and tobacco.

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Mosaic virus -

Mosaic virus is more common in hot weather and causes mottled yellow and green leaves that are sometimes curled and distorted.

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Mosaic virus -

There are no chemicals to control this, so make sure to remove and destroy infected plants, roots and all. Also, avoid planting susceptible plants in the same area for at least two years.

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Powdery mildew -

Caused by a fungus, powdery mildews leaves a white, dusty coating on stems, leaves, and flowers. It affects a number of plants, such as lilacs, apples, daisies, and roses.

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Powdery mildew -

To get rid of this disease, remove and destroy the infected leaves to reduce the spread of spores. Make sure to also provide the plants good drainage and air circulation. Also, make sure to only water mid-morning to allow foliage to dry before evening.

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Powdery mildew -

You can also buy commercial fungicide for powdery mildew, or make your own spray. Just mix one tablespoon of baking soda and one quart of water.

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Rust -

Rust is another fungal disease that's easy to spot, as it forms rusty spots on leaves and stems. The spots eventually turn black.

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Rust -

There are varieties of rust that can attack plants such as day lilies, roses, hollyhocks, and tomatoes. Even grass can be affected.

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Rust -

Luckily, there are solutions, such as fungicides. But you can prevent it as well by gathering and destroying any infected plants, keeping them from spreading the fungus.

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Snow mold -

Snow mold is a fungus that appears in cold, moist conditions beneath the snow. It attacks turfgrass, and is only visible after the snow melts.

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Snow mold -

The main symptom of snow mold is light tan areas of matted grass caused by threads of mold.

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Snow mold -

To get rid of it, rake the matted grass to break up the mold and allow new growth. During fall, make sure the last cutting is shorter to discourage tall grass blades from falling over and contributing to matting.

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Sooty mold -

Sooty mold is a fungi that grows on the sticky deposits, called honeydew, left by plant-sucking insects. It blocks photosynthesis on leaves, preventing growth, and causing them to drop off prematurely.

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Sooty mold -

To deal with sooty mold, one has to combat the plant-sucking insects leaving the honeydew, such as aphids, leaf hoppers, and mealybugs.

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Sooty mold -

Spray the bugs with insecticidal soap or neem oil. Eventually they'll disappear and leave your plant alone and mold-free.

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Verticillium wilt -

A fungal disease, verticillium wilt affects tons of species of trees, shrubs, edibles, and ornamentals. It's caused by pathogens that can live in the soil for years.

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Verticillium wilt -

The pathogen eventually spreads into the plant  through the roots, and clogs the vascular system, which causes the leaves to wilt, turn yellow, and fall off prematurely.

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Verticillium wilt -

Fungicides won't work, so instead remove and destroy infected annuals, perennials, and edibles. Make sure to sterilize cutting tools with a 10% bleach solution between cuts.

Sources: (The Family Handyman) (Proflowers)

See also: These plants and flowers can kill you

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