Indentifying Plant Diseases

The risk of plant disease is much lower in a hydroponic garden due to the lack of soil. Bacteria thrive in soil, spreading blight and other plant diseases around the garden. Those pesky bacteria cannot thrive as well in a soil-less hydroponic system.

In order for plant disease to occur your garden must present three elements:

  • Host plant
  • Pathogen
  • Environmental conditions favorable to bacteria

Preventing Disease

Disease spreads in certain environmental conditions, such as crowding, high levels of humidity and lack of sunshine. Nutritional deficiencies, out of balance pH levels and toxicity also leave a plant more susceptible. Too many nutrients or not enough nutrients can cause these conditions.

The best way to prevent disease is through routine care and maintenance. Watch for signs of disease, and act quickly when detected.

Many of the products marketed to combat plant disease include harmful chemicals. This can be a major problem with hydroponic gardening, as these chemicals will get into the nutrient solution and into the plant cell. Indiscriminant use of these products can harm your harvest.

What Can You Do About Plant Disease?

Start with gentler solutions and avoid harsh products at first. One common solution to the appearance of plant disease contains simple household ingredients:

  • water
  • baking soda
  • lemon juice
  • tiny amount of dish detergent

Mix these ingredients into a spray bottle and apply or mist onto the infected foliage or stem. Always cover the reservoirs or areas that hold your nutrient solution; soap bubbles from the dish detergent can wreak havoc there and damage your plants even more.

Check out these common diseases and the favored methods of attack.

Powdery Mildew

This fungus comes out in white or grayish spots or patches on foliage, often underneath. Powdery mildew thrives in high levels of humidity and slowly shrivels leaves.
Treatment – Use homemade detergent spray as described above.

Root Rot

This type of fungus rots away the roots, destroying the plant from the bottom.
Treatment – Cut off the damaged roots and spray with a gentle fungicide product.

Early Blight

This disease weakens your plants and leaves dark brownish spots and patches on the stem, foliage and fruit.
Treatment – Best treated with harsh chemicals like zineb and maneb.

Black Mold

Look for gray or sooty black patches on the plant.
Treatment – scrape off mold and wash foliage and stem gently.


This fungus results from over-watering and can be detected by the dark smearing and shriveled foliage.
Treatment – Remove or cut off damaged foliage and spray with a gentle fungicide.

Damping Off

This fungus affects the base of the stem and causes plants to flop over and often die.
Treatment – Cut off damaged sections and replant any affected plants in the surrounding area. Use fresh growing media and clean pots for replanting.


Fuzzy whitish-gray patches on the leaves and foliage are signs of this disease, often resulting from poor ventilation. It is not often seen in hydroponic gardens.
Treatment – Remove diseased or damaged sections and improve ventilation.


This fungus is often found on the underbelly of foliage, presenting a powdery red patch that may be bumpy or slightly raised. High levels of humidity encourage growth of rust and it can spread quickly through your garden.
Treatment – Use harsh chemicals, such as maneb or zineb, in small amounts to remove the rust spots.

Club Root

This disease transforms previously healthy roots into balls or clumps of club-shaped tubers, resulting in stunted growth.
Treatment – Dust the plant with fungicide.

Crown and Stem Rot

This fungus is easily detected by the condition of the plant, which becomes pulpy and subsequently rots.
Treatment – Remove rotted sections of the plant and spray the balance with fungicide.

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