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Most
pests can't tell the difference between a hydroponic and soil based
plant so will happily eat either. The advantage of hydroponics is that
the plant is usually more vigorous and strong than its soil-based
counterpart so is better able to cope with attack. In the case of
extreme insect infestation you can resort to the usual organic pest
control methods. Foliar or systemic control can be used, systemic
liquids being added to the nutrient.
Bacteria,
fungus and mould also can't discriminate between conventional and
hydroponic plants but thankfully diseases are fairly uncommon in
hydroponic systems as long as they are well maintained and kept clean.
Should a diseased plant be identified it should be removed and
destroyed. Those remaining should be treated if possible, although it
may already be too late as spread is often rapid. The nutrient should
also be flushed and clean water circulated thought the substrate if
present. Fresh nutrient can then be added. The shared environment means
that disease will spread more quickly in a hydroponics system than in
pot based cultivation.
Symptoms
of deficiency or excess are shown in the tables below, the most common
being nitrogen, magnesium and iron. If a problem is suspected the
nutrient should be flushed and replaced with a fresh mix. Foliar spray
can be used and is particularly effective for nitrogen and magnesium
deficiencies. These
deficiencies are most likely to be the root cause of your problems once
basic hygiene and pest control have been ruled out. The main symptoms
and causes are listed in the tables below.
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Macronutrient
Imbalance Symptoms
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Mineral
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Deficiency
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Excess
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Nitrogen
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Older
leaves turn yellow. Remaining leaves are often light green. Stems
may also yellow and may become spindly. Growth generally slows.
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Plant
very vigorous becoming very leafy. Leaves turn dark green. Fruit
fails to ripen.
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Magnesium
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Slow
growth and leaves turn pale yellow, sometimes just on the outer
edges. New growth may be yellow with dark spots.
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No
direct visible changes. May inhibit Calcium.
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Calcium
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New
leaves are distorted or hook shaped. The growing tip may die
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No
direct visible changes. May inhibit other minerals at high pH
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Phosphorus
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Small
leaves that may take on a reddish-purple tint. Leaf tips can look
burnt and older leaves become almost black. Reduced fruit or seed
production.
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No
direct visible changes. May inhibit Copper and Zinc
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Potassium
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Older
leaves may look scorched around the edges or wilted. Yellowing
between the leaf veins develops
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No
direct visible changes. May inhibit Manganese
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Sulphur
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New
growth turns pale yellow, older growth stays green. Stunts growth.
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Slow
growth and small leaves
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Micronutrient
Imbalance Symptoms
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Mineral
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Deficiency
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Excess
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Iron
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Pale
new growth. Leaves yellow between veins and die from the edges.
Blossom drop.
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Only
visible if foliar spray used, then black spots may be present.
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Boron
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Poor
stem and root growth. Buds may die.
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Leaf
tips yellow then die.
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Copper
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Stunted
growth. Leaves can become limp, curl, or drop.
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No
direct visible changes. May inhibit Iron
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Manganese
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Growth
slows. Younger leaves turn pale yellow between veins. May develop
dark or dead spots. Leaves, shoots and fruit diminished in size.
Failure to bloom.
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No
direct visible changes. May inhibit Iron
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Molybdenum
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Older
leaves yellow, remaining foliage turns light green. Leaves can
become narrow and distorted.
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Leaves
may turn bright yellow.
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Zinc
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Yellowing
between veins of new growth
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No
direct visible changes. May inhibit Iron
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