COMMON PLANT DISEASES

So maybe you haven't found bugs and pests in your hydro garden, but other mysterious things are going on...










Aside from common plant pests, there are several different types of common plant diseases that can threaten your new garden. Among these plagues are mildew, molds, viruses, and algae. Most of them are caused, as you might suspect, by high humidity and stale air.

Excessive humidity is the leading cause of fungus and mold outbreaks, so it pays to keep an eye on the humidity level of your garden environment. Use a hygrometer ($6 at Walmart) and check the RH (relative humidity) periodically. You might think that a hot, humid atmosphere (like an orchid house) might also be the best for your veggies, but that is not the case. Hydroponic vegetable crops actually do best at a RH of 50-60%; 80% as a maximum.

Circulating fan

You can reduce the humidity in your grow area by using an air conditioner, and also an inexpensive fan to keep the air circulating. It is best to see the leaves of your plants moving very slightly, 24 hours per day. This flushes out stale air and helps to prevent the formation of those dreaded mildews and molds, as well as other
common plant diseases.

Also be careful not to over-water your plants, and make sure the media used is draining well between feedings. Soggy plant media makes a great host for disease and algae growth.

THE MOST COMMON PLANT DISEASES

Below we list the most common plant diseases you might find in your hydroponic garden:

GRAY MOLD (BOTRYTIS)

GRAY MOLD (BOTRYTIS)

A sooty, grayish-white growth on the leaves (kinda like hair or lint). This is the most common fungus caused by excessive humidity, and is usually fatal once it takes hold. If you catch it as a fresh outbreak, you may be able to fight it off. How?

  • Take a soft, dry cloth and remove the mold from the leaves.
  • Scour the garden for dead matter and debris and remove it.
  • Decrease humidity and increase air circulation and ventilation.

POWDERY MILDEW

POWDERY MILDEW
POWDERY MILDEW on tomato leaf

First appears as small white spots on the tops of the leaves, but then progresses a fine, pale gray-white powder, all over. Growth slows, leaves turn yellow and the plant dies. Powdery mildew is caused by cool temps, dim light and high humidity. How to treat this common plant disease?

  • Decrease humidity
  • Increase air circulation and ventilation
  • Increase light intensity
  • Consider one of the fungicides listed below

DAMPING OFF

DAMPING OFF

This common plant disease usually affects your newly planted seedlings, and is caused by too-moist planting media. You must keep those grow-cubes drained off, not just sitting in water. Damping off first appears as a wet-looking dark stem. The seedling then collapses at the "soil line", and falls over dead. There is no cure, once damping-off strikes. So how do you prevent it?

  • Use only sterile, fast draining media for your seedling nursery.
  • Consider routine application of all-purpose fungicides below.

ALGAE

ALGAE

You know what this looks like; a greenish tinge that covers the top of the plant media, and may infest your nutrient vat, too. Algae is really not a serious problem, however it is unsightly and signals to you that conditions may be a little too moist in there.

Algae growth is caused by stagnant water, excessive moisture, and light. You can prevent it from attacking your nutrient solution by using only opaque tubing in your system (not clear). Cover any ports in the nutrient reservoir with hatches or duck tape to keep light out. Other measures that may help:

  • If using fine, porous medium, like coco coir or perlite mixes, top each pot with 1-2" of leca stones to provide a
    dry barrier. This not only holds down the lighter media, it helps prevent algae and fungus gnats.
  • Scrape off the algae and correct the overly-damp conditions that caused it.
  • Sterilize your system between plantings with 10% bleach solution.

WILTS

[wilt-disease] Verticullum Wilt and Fusarium Wilt

[wilt-disease] Verticullum Wilt and Fusarium Wilt- Wilt diseases start as small spots on the leaves of your tomato, peppers or eggplants. The lower leaves start to curl up, dry out and wilt. Sometimes, portions of the plant may wilt suddenly. You can prevent these wilt viruses by using only fresh, clean medium for each planting, and using resistant varieties of tomatoes (labelled V or F).

If you do contract one of these common plant diseases, you cannot re-use the media, or the wilts will just reappear in your new planting. You might want to try treating the wilts with DCM Bio-Fungus, but honestly, it is best to just get that diseased plant OUT of your hydro setup, and disinfect well before starting your next new garden.

TOBACCO MOSAIC VIRUS

TOBACCO MOSAIC VIRUS

This virus remains on tobacco leaves for years. It can be introduced to your garden by the hands of smokers. It can afflict peppers, cucumbers, and tomato plants, and it is very hard to eradicate if you are unlucky enough to contract this plague. Prevention is the keyword here:

  • Never allow smoking in your hydro grow room.
  • Smokers must wash their hands thoroughly with soap and water before touching anything in your garden area.
  • Even this might not prevent an infestation. Best to exclude smokers if you are fond of heirloom tomatoes. May be just the incentive they need to quit  :-)

Some relatively safe organic Fungicides:

You may need to resort to stronger measures to control these common plant diseases:

Safer's Garden Spray
Serenade Garden Spray

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