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Identifying Different Types of Plant Diseases

“To plant a garden is to believe in tomorrow.” – Audrey Hepburn.

When it comes to improving your property’s beauty and surrounding environment, our trees take a big chunk of the credit. Its lush green view can simply “swipe up” our moods, making us feel calm and happy. Did you know that the colour green can help alleviate bad moods, depression or anxiety? Therefore, its maintenance in a cost-effective and natural way is crucial. 

Taking care of your backyard’s trees is making sure that they’re trimmed or pruned on a regular basis, therefore keeping any disease infestation in check. Tree diseases are generally caused by fungi, bacteria or virus infestations. These diseases interfere with the tree’s growth, development and natural functioning. Since most plant diseases have similar symptoms, it can sometimes be very difficult for a layman to figure out what caused a specific illness.

This blog post will give you a brief outline of some common diseases that are robbing your trees of their safety and what can be done about it.


Fungi are plants that cannot produce their own food and must depend on other plants and animals (dead or living) for their survival. While some fungi are beneficial to plants, other varieties may harm or kill your tree’s leaves, branches, stems, or roots. They may attack and grow as a mass of fine threads into and through plant tissues, consuming plant cells as they spread.

Fungi are spread by:

  • wind
  • water
  • infected soil.

Common Fungi Disease symptoms are:

  • spots
  • rot
  • mildew and mould
  • a furry appearance when they are mature and produce spores (this is one way of telling the difference between fungal and bacterial infections).

7 Common fungal diseases

  1. Blackspot disease

Symptoms – Black/dead regions on stems, leaves, and fruits.

Example – blackspot on rose plant

  1. Rust

Symptoms – On the top surface, there are yellow or brown flat dots, while on the bottom side, there are raised patches.

Plants commonly affected- rust spots on Chrysanthemum leaves

  1. Powdery mildew

Symptoms – white spots on a leaf surface

Plants commonly affected- powdery mildew on pumpkin leaves

  1. Downy mildew

Symptoms – Pale regions on the top side, soft white growth on the bottom side of the leaf

Plants commonly affected- grapes, onions, cabbage seedlings

  1. Mould

Symptoms – A rotting tissue that becomes grey or brown

Plants commonly affected: Greenhouse crops, grapes, strawberries, etc

  1. Wood rot

Symptoms – Inner tissue of stems and branches is weakened. Leaves may turn silver

Plants commonly affected – stone fruit

  1. Damping

Symptoms – Seedlings rot and die

Plants commonly affected – young seedlings of many plants

Fungal diseases can be prevented by:

  • Maintaining strong hygiene (removing infected plant parts)
  • Keeping plant-care equipment clean
  • Ensuring that plants in greenhouses have enough air, and avoiding soaking plant leaves with fungicides
  • Planting disease-resistant plants


Bacteria are single-celled organisms. They cannot produce their own food, therefore they depend on dead organic matter for energy.

Although many bacteria are helpful for plants, some of them can cause diseases. Bacteria spores multiply at a rapid speed, allowing a plausible disease to spread eventually at the same rate. This rapid spread can quickly escalate from one plant to an entire harvest.

Bacteria are spread by:

  • water
  • insects
  • infected seeds
  • infected soil.

It might be difficult to distinguish between bacterial and fungal attacks.

Common bacterial disease symptoms include:

  • spots
  • lumps
  • withered leaves
  • collapsed tissue or rot.

4 Common bacterial diseases

  1. Cankers

Symptoms – gradual decay of infected tissue, dying bark, oozing out of gum from the bark

  1. Galls

Symptoms – lumps, ball-shaped forms

  1. Soft rot

Symptoms – Damaged plant areas becoming moist

  1. Fire blight

Symptoms – Withered leaves and dieback


Viruses are not true cells. They’re made up of genetic material encased in a protein coat. Viruses can only multiply by infecting and enslaving live plant or animal cells, and then using the host cells to multiply. They replicate extremely fast, which means that a viral disease may rapidly spread across a crop.

Viruses are spread by:

  • insects such as aphids
  • infected plants or cuttings
  • infected soil
  • tools and hands
  • seeds.

Common virus disease symptoms are:

  • stunted, curled or deformed leaves
  • mottled (mosaic) or patterns on leaves
  • streaked petals.

What’s the solution?

Steps to Effective Disease Treatment: Inspect, Identify, and Cure

Once you’ve identified the source of the disease and its severity, you have two options. 

  1. If it is a slow-spreading manageable disease you may wish to consult an expert to help treat the affected plants. With help from an expert or the internet, you can design n a customized and multi-pronged disease treatment plan targeted to the type of tree, the specific pathogen, and the site conditions.
  2. In some cases, the best course of action may be to eliminate the disease by removing affected plants. For this, it’s a good idea to hire a qualified arborist

Assess and Improve the Site Conditions.

The environment or site conditions in which your tree is growing can have a big impact on its resilience — and sensitivity — to diseases and other challenges. For example, Excess moisture promotes the spread of many tree diseases. Inadequate sunlight and air movement, as well as poor drainage, can induce chronic moisture retention in the tree’s leaves, stems, or root system, which can contribute significantly to its unhealthy conditions.

As poorer environmental conditions can make preventative measures less effective, your arborists may offer suggestions to improve the site before starting such treatments. Pruning and trimming the affected tree(s) – and the surrounding trees – can increase the scope of sunlight penetration and airflow by opening up its crown.

Another example: Root rot is a harmful illness caused by inadequately drained soil. As a result, increasing drainage is a critical first step toward resolving the issue in future growing seasons.


Professional tree care can help you in maintaining healthy, beautiful trees that are a valuable addition to your home. Whether you have concerns about one or more of your trees, or just want to learn more about tree care services in Canterbury, feel free to contact us.