Plant diseases are usually produced by different kinds of organisms. Diseases that affects the leaf and the stems are bacteria, fungi or viruses. Soilborne diseases on the other hand are caused by various fungi. Bacterial diseases are caused by bacteria who are unable to manufacture their own food thus they depend on the host plant for food depriving the plants of the nutrients necessary for a healthy growth.

Fungal diseases are the most widespread plant maladies. Fungi parasitically obtain their food from green plants, causing diseases in the process. Fungi produces spores in great number which are tiny reproductive bodies. These spores can be carried by wind or water. Each spore will germinate and grow producing new infections. Viral diseases are viruses capable of invading plant tissue and reproducing in it. Viruses can be spread by aphids, leafhoppers and thrips. Even humans can spread viruses by propagating virus-infected plants.

Other factors that causes this are the plants own interaction with unfavorable environmental factors. This includes air pollution, a deficiency or excess of sunlight which is its main source of nutrients. It can also be the climate. Climate adaptability in plants is very important. Plant disease can be caused by climate which is too hot, too cold, too dry or too wet.

Kinds of Leaf and Stem Diseases

1. Anthracnose - infects leaves, produces large, irregular brown blotches which causes premature dropping of leaves.

2. Black Spot - it appears on leaves and stems as roughly circular spots of black with fringed edges, usually circled with yellow.

3. Dutch Elm Disease - also known as DED. Can be spread from infected trees to nearby healthy ones by natural root grafting.

4. Fireblight - it is carried to blossoms by splashing water, flies and other insects. Infection can also enter a plant through any fresh wound in the bark or foliage.

5. Leaf Spot - it is red, brown, yellow, or black disease spots on leaves and stems. Severe infection of this disease can cause some plants to defoliate.

6. Peach Leaf Curl - the curled and distorted leaves may be tinged with red, pink, yellow or white. Later they may become covered with white spores that can be carried by the wind to other leaves or plants.

7. Powdery Mildew - if first appears as small gray or white circular patches on plant tissue, spreading rapidly to form powdery areas of fungus filaments and spores.

8. Scab - the scab fungus differs from other leaf-infecting fungi in that the dark spots on leaves represent fungus growth on the foliage rather than areas of dead tissue.

9. Rust - this disease is specific to a certain type of plant. Rose rust will not infect hollyhocks and vice versa.

Soil borne Diseases

1. Damping Off - the stem of a seedling collapses at or near the soil surface and the seedling topples. It can also rot the seedling before it emerges from the soil or causes the seed to decay before sprouting.

2. Oak Root Fungus - the fungus kills its host by gradually decaying the roots and moving into the main stem, where it girdles the plant.

3. Root Rots, water Molds - the damage to roots from overwatering is, in almost all cases, not caused by water itself but by water-mold fungi that thrive when free water stands too long around roots - especially when soil is warm.

4. Verticillium Wilt - it invades and plugs the water conducting tissue in the roots and stems. A common symptom is a wilting of one side of the plant.

Ways to Control Plant Diseases

As with any kind of diseases, prevention is still the best line of defense. As much as possible choose plants that are disease resistant. Also make sure that planting locations and conditions don't encourage diseases.

There are products readily available in the market for this purpose. One classification are called preventives - as the word suggest it prevents diseases from occuring, but these products are ineffective once the disease are already established. The other classification is called eradicants - once the disease is established, eradicants are helpful in controlling them.

Before using any of these products, it will be wise to read the labels very carefully. Be sure to apply the products only if the plant is listed. It can cause damaged if applied to inappropriate plants.

Here are some of these products and the common disease they each control.

1. Sulfur - used to prevent powdery mildew, scab and rust. It is one of the oldest and safest fungicides

2. Lime Sulfur - It controls some mites, scale insects and thrips. Also used to prevent various leaf spots, peach leaf curl, and powdery mildew.

3. Captan - for prevention or eradication of damping-off, leaf spots and many other fungal diseases.

4. Triforine - for prevention or eradication of powdery mildew, rust, black spot and a variety of other diseases.

5. Copper Compounds - often used to prevent fireblight, peach leaf curl, and shot hole diseases.

6. Chlorothalonil - it prevents diseases on lawns, fruits, vegetables and ornamentals.

7. Triadimefon - effective against azalea petal blight. It can also prevent powdery mildew, rust and some lawn diseases.