Download ABIOTIC CAUSES OF ILL

ABIOTIC CAUSES OF ILL-HEALTH
IN TREES
• Abiotic (non-living) causes of ill health in trees
are predominantly weather-related.
• Additional factors include chemicals.
• Man also has a role to play (as always!).
Water
• Too little leads to water deficit through
drought.
• Wilting etc.
• Too much (flooding) causes the oxygen to be
driven out of the soil, leading to roots
suffocating.
• Symptoms show as twig and crown dieback
etc.
Temperature
• Too hot – ‘sun-scorch’ on thin barked species.
• Beware of over-thinning trees.
• Cracks and splits in bark (similar to frost damage).
Also reddening of the most sun-exposed leaves,
or red-brown necrotic areas
• Too cold – freezing damage.
• Sap freezes and as ice crystals form and expand,
they rupture the cell wall, killing the cell.
• Cracks/splits in bark. Brown shrivelled foliage.
• Symptoms like sun-scorch, investigate the cause!
Fire-damage
• As with temperature, Fire damages sensitive
tissues and can kill plants.
• Brown, scorched foliage.
• Blackened, burnt bark etc.
Wind
• Asymmetrical shape of crown, due to
predominant wind. Looks like tree is folding
its ears back flat.
• Excessive transpiration from leaves, so often
see discoloured and tattered/torn, with
marginal necrosis.
• Severe winds cause splits, cracks, broken
branches, or uproots the whole tree.
Gas Injury
• Gas in soil (broken pipes) causes similar
symptoms to water stress – slow growth,
small leaves, wilt, premature leaf drop.
• Roots often have a bluish colour inside –
identifying feature.
• If atmospheric gas release, leaves are
discoloured, with marginal necrosis
Lightning
• ‘Hot bolts’ have temperatures of over 25 000
degrees F (14 000 degrees C).
• This can cause whole tree to burst into flames.
• ‘Cold lightning’ strikes at 20 000 miles/second,
and can blow the tree apart, splitting the trunk,
blowing bark off.
• Often a continuous groove spiralling down stem
as lightning ‘grounds’.
• Nearby trees can have damaged roots and show
signs of damage later.
Hail
• Particularly damaging to newly emerged
leaves.
• Leaves shredded/torn.
• ‘Shot peppered’.
• Twigs broken or damaged.
• Bark bruised, broken or scarred, leading to
infection by other pathogens.
Mechanical injury
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Strimming, mowing etc.
Damaged bark, roots etc.
Broken branches.
Tree ties left too long – strangulation of stem.
Often stem above restriction is a greater
diameter than below. Stem fails at this weak
point.
Nutrient deficiency
• Macro nutrients – N, P, K
• Micro nutrients – Manganese, Magnesium,
Phosphorus, Zinc, Iron.
Salt damage
• Brown foliage retained on tree, often on one
side of crown.
• Sparse foliage, more than one leaf flush.
• Marginal necrosis, typically on the tips and
edges of the older leaves.