This type of hydroponic system provides nutrient solution constantly. A submersible pump is used without a timer, moving solution through a tube and into your growing tray. It flows around…
This passive hydroponic system contains no moving parts. Nutrient solution moves along a wick from the reservoir to the growing media. Most gardeners using this system opt for pro-mix, coconut…

In order to enjoy a thriving garden, you must learn to correctly diagnose nutritional deficiencies in your plants. Detecting symptoms allows you to respond and fix the issue before your plants experience major stress.

Signs and symptoms vary depending on the growth stage, plant species and other factors such as climate and growing conditions. Gardeners need to become familiar with the wide range of deficiencies and understand how they can affect each crop.

How to Tackle Plant Deficiencies

Use a plant journal to record the conditions of your garden, making special note of any strange or unusual appearances or behavior. Photographs work well for this and can be stored on your computer or smartphone for fast access.

Pictures allow you to compare the appearance of your plant over time and can help with problem solving. Share your pictures with other gardeners and gather advice and tips from experienced growers. Keeping an accurate record, through text or images, helps to record the response to treatment as well.

Common Plant Deficiencies

Deficiencies are not the same as diseases. Watch your plants for signs of the following common plant deficiencies:

Nitrogen (N) Deficiency

Plant roots and top exhibit restricted growth and lateral shoots. They may become spindly and foliage may turn light green and eventually yellow, beginning with older leaves and moving to the younger foliage. Older foliage falls off early.

Phosphorous (P) Deficiency

This looks very similar to a nitrogen deficiency, although the leaves turn more of a bluish color or a darker green. Both nitrogen and phosphorous deficiencies can present purple streaks between the veins and underneath fresh leaves.

Potassium (K) Deficiency

Look for signs of chlorosis (patches of yellow or white on the leaves that results from insufficient chlorophyll) and limited scorching or necrotic spots. This scorching moves toward the middle of the plant and will spread into fresh growth as the deficiency increases.

Calcium (Ca) Deficiency

This deficiency shows up in a number of ways, including slight detection of chlorosis, die-back at points of growth and scorching around new leaves. The scorched and die-back sections will not dry out or crumble in your hand.

Boron (B) Deficiency

Similar to calcium deficiency, a lack of boron results in scorching on fresh growth and die-back. But you'll also detect rough, cracked and hollowed stems and an increase in lateral shoots.

Magnesium (Mg) Deficiency

Look for mottling, marbling and chlorosis on older foliage, which moves toward fresh leaves as the deficiency increases. Yellow patches show up between the veins and near the center of the foliage, spreading to the outer edges as time progresses. Certain plants also present necrotic spots and some scorching on foliage.

Sulfur (S) Deficiency

This deficiency looks much like nitrogen deficiency, but plant stems become thin, woody and tough. They grow longer, but not thicker and the foliage may turn an orange-red color instead of the yellowish tinge common with nitrogen deficiency.

Iron (Fe) Deficiency

Immature foliage presents mottling between the veins, and with severe deficiencies, fresh leaves contain little to no chlorophyll. Mottling often starts at the base of fresh leaves and presents a yellowish streak up the middle of the leaf.

Manganese (Mn) Deficiency

This deficiency is difficult to distinguish from an iron deficiency. You may notice stunted blossom development on fruit plants or yellow blossoms. This increases as the deficiency progresses and necrotic spots often develop between the foliage veins.

Zinc (Zn) Deficiency

Depending on the plant species, this deficiency presents mottling between the veins of old or new foliage. Eventually, the mottling spreads throughout the plant and may resemble the symptoms of manganese or iron deficiency, especially if the onset is sudden. You will notice small foliage developing, unlike the other two deficiencies.

Copper (Cu) Deficiency

This deficiency results in wilted leaves on the crown of your plants, following by mottling and necrotic spots on the foliage. You may see puckering and chlorosis, and could detect an absence of knots on the stem.

Molybdenum (Mo) Deficiency

This deficiency appears much the same as a nitrogen deficiency, especially when present in legume plants. Because molybdenum moves around a plant, symptoms are found in foliage of any age. The most common symptoms include irregular formation of foliage, often called whiptail, as well as mottling between the veins and chlorosis in older leaves.

 

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.

Anthracnose

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.

Botrytis

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.

Rust

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.

Plants grown in hydroponic gardens are susceptible to disease and pests, just like in soil-based systems. If you ignore maintenance tasks and avoid dealing with pests and disease, you'll end up with spindly growth or dead plants. And losing fruit and vegetable plants means losing a potential source of healthy food.

Management of a hydroponic garden can be tricky, since certain diseases and pests thrive in the moist setting. Plants are kept moist in hydroponics, either immersed (as in true or traditional hydroponics) or continually misted with water (as in aeroponic systems). Other systems use a wet growing media like sand or perlite.

Hydroponic gardeners use the wide selection of methods and products available to combat pests and disease that crop up in their gardens.

How to Control Pests and Disease

Beneficial life forms present a popular and successful way to keep pests away from your hydroponic garden. These life forms combat certain types of fungi and bacteria, crowd out or eat spider mites and other pests, and do it all without damaging your plants.

Pesticides are available as well, including non-toxic soaps that have been used successfully for generations. Botanicals include plant compounds combined into efficient formulas for easy use. Botanicals also break down naturally and leave nothing behind to damage your plants.

Neem oil is another good choice for pest control, attacking more than four hundred pest types often found in both traditional and hydroponic gardens. Spray oil onto foliage to chase pests away. Insects absorb the natural oil and are unable to reproduce, which results in a steady decrease in population. Commercial pesticides containing neem oil can be used for serious infestations.

Many gardeners use pyrethrum to control pests and disease. This compound is flower-based, extracted from plants and included in several commercial-grade insecticide products. Although pyrethrum is safe when applied properly, gardeners should read labels on all products.

Azatrol is another insecticide compound that easily controls common pests in your garden.

Common Pests and Disease

Gardeners battle several common problem insects, including:

  • white flies
  • aphids
  • mites
  • mealy bugs
  • thrips

Several diseases have earned a reputation for trouble in the garden, including:

  • powdery mildew
  • fungal diseases
  • rust
  • crown and root rot

Hydroponics present continuous moisture, and many bugs thrive in that environment. By using organicides and fungicides, gardeners can make that environment unappealing. Adding sulfur-based compounds helps to control many other pests not necessarily drawn to the moisture.

You must take care when handling a pest infestation. Handpicking larger bugs and larvae is an excellent measure, but the lack of soil makes hydroponic plants particularly vulnerable to mishandling. Be careful and be aware of your effect on the leaves, roots and stems.

Mildew and fungus naturally form in the moist conditions of a hydroponic garden. Keep foliage dry and roots wet to avoid these diseases. If you spray insecticide on your vegetables or plants, always allow the foliage and stems to dry, often under a grow light. You may need to temporarily relocate aeroponic systems to take care of this.

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DMC Firewall is developed by Dean Marshall Consultancy Ltd