Common Plant Disorders, Diseases and Pests…Top 10 Lists

“What’s wrong with my plant?” You ask as you walk through your garden and¬†notice subtle indications of malaise to complete devastation of what was recently a thriving healthy plant or garden. It can be overwhelming to identify what exactly has gone wrong. The key is an accurate and speedy response to symptoms. An expert can be hired or a guide on plant ailments can be a great tool to assist you in the task of identification, treatment and prevention such as the excellent comprehensive book title¬†“What’s Wrong With My Plant?” by Steven Bradley.

This post lists a basic top 10 overview of disorders, diseases and pests.

A Plant Disorder stems from the physiology of the plant attributed to environmental factors (such as erratic watering, inappropriate lighting and temperature ranges ) and nutritional deficiencies. Major nutrients are nitrogen, phosphorus and potassium (potash) as well as additional trace nutrients in lesser amounts. Each plant requires a fertilizer in different combination amounts.

The 10 most common Plant Disorders are:

Bolting – premature growth

Chemical Damage – misapplication, salt on pathways, paint fumes, manure, herbicides…

Drought – vegetable plants are most vunerable

Frost – formation of ice crystals in the plant cells

Nutrient Deficiency – an imbalance of soil and fertilizers

Pollution – carbon monoxide is a main culprit, harm is dependent on the concentration

Sun Damage – too much heat and light exposure can, thin barked trees such as cherry and maple are effected, tomatoes ripen unevenly.

Waterlogging – an issue with mainly indoor plants. Too much water eliminates oxygen in plants soil.

Windchill – one particular side of a plant may eventually brown as the wind displaces water and it worsens if that side is water logged or frozen since the roots in malfunction will not be able to replace the moisture.

Windrock – young taller plants are effected especially in exposed windy areas with poorly drained soil. The wind causes the motion of the top growth to loosen new roots resulting in saucer shaped depression susceptible to water logging.

A Plant Disease is a an pathological condition caused by other organisms such as bacteria, fungi or viruses resulting in the impairment and mortality of a plants life. Typical symptoms are discoloration, wilting and deformity.

The 10 most common Plant Diseases:

Canker/ Blight – dark sunken lesions that ooze bacterial slime. Causes death to reproductive area of plant.

Downy Mildew – yellow or pale green discoloration on tops of leaves. More resistant due to milder winters.

Honey Fungus – one of the most lethal fungal disease attacking the root. Initial symptoms is leaf yellowing, then branches dying back. Spread by thin black roots in soil or spores from nearby honey coloured toadstools.

Leaf spots- there are numerous bacteria and fungi that cause spots. Usually circular and grey and brown in colour with a yellowish circle or depressed tissue area depending if its bacterial or fungal.

Powdery Mildew – the most recognizable as it looks like a powdery felt-like growth on the top side of its host.

Moulds- there are only a few moulds. The fungus attacks leaves, flowers, fruits and stems – causing decay with its grey fur like mould.

Root Rots – “an enormous group of diseases” that affects the roots or base of plant. The diminishing of cells that compose plant tissues result in ultimately a rotting mass.

Rusts – a fungal disease with yellow/ green blotches on upper side and clusters of blister like formations which release more spores.

Viruses – a generic term for many encompassing diseases. Complex combination of symptoms and sometimes none at all. Named for their particular characteristic symptoms such as “leaf roll virus”.

Wilts – wilting of stems and shoot tips.

A Plant Pest is a creature that harms a plant by feeding on it in various ways and sometimes leaving byproducts or acting as carriers to even more diseases.

The 10 most common Plant Pests:

Ants – sudden wilting may be an indicator of colony building beneath plants removing soil and causing root damage.

Aphids – come in various colours and suck sap. Stunted growth and distortion of leaves and shoots. These reproduce exponentially.

Beetles – shiny armour like appearance. Some are beneficial but are notorious for spreading Dutch Elm disease by laying eggs.

Caterpillars – a larval stage of a butterfly or moth. Various species feed on different parts of a plant.

Eelworms Рmicroscopic worm-like creatures that are vital in breaking down organic soil matter but also cause  destruction by invading the internal path of a plant. Moist conditions are required as they travel along films of moisture.

Mealybugs Рtiny and oval with a white fluffy wax. Mostly found indoors. Usually infect inaccessible areas such as leaf axils and bark crevices.  It feeds and excretes a sticky substance that becomes black after mould colonizes.

Mites – a relative of the spider and often beneficial to the garden but in other cases cause harm by sucking sap which causes speckling of leaves with a silken web in more severe cases.

Scale Insects – shell like scale which the eggs are laid under. Hatched insects go on a feeding frenzy and excrete a sticky “honeydew” for mould to colonize.

Slugs and Snails – Mostly found in alkaline soils. These slimy culprits create irregular holes in plants and attack even below ground and on new growth. Eggs often survive the winter and have been known to “home’ in areas so they will return to the crime scene even if you just kindly relocate them.

Clearly this area of plant life is complex and requires in depth knowledge and integrated care for pest and disease management.

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