Top 5 Plant Killing diseases and Protection

Written By: Mark Kay

Maintaining a garden that is entirely free from pests, disease, and weeds is a very arduous task. There are several different microorganisms found in the garden, but most are usually small enough that they go unnoticed and cause little harm to the existing or new plants.

If you have several ornamental or edible plants in your garden, then you must have a clear strategy to identify the diseased plant and take immediate action to stop the spread of the disease.

Let’s find out the most common type of diseases to the plant and the ways to prevent and treat them.

Why does a garden get infected by pests and microbes?


Plants are a rich source of nutrients to several insects and pests, especially soil that hosts several types of microbes. Some of them are beneficial, while some aren’t.

For a plant to get infected by a disease, it requires three elements.

 – A disease spreader such as microbe or pest– Susceptible host plant– A favorable external condition such as weather that helps the growth of the disease.It may not be practical or even possible to eliminate all disease-causing microbes from your garden. But you can regularly inspect plants and take action to control it before it takes a stronger hold in your garden. 

What are some common ways to prevent the plants from catching the disease?

A tip to prevent disease is to grow newer plants that are free from any illness. You can do it by carefully inspecting plants that you are considering purchasing and making sure that it’s disease-free.

You can buy hybrid plants bred with resistance to common diseases. Moreover, you should also take proper care of soil by providing adequate drainage, air circulation, fertilization, and enough spacing between plants.

A word of caution, don’t use too much nitrogen in the garden as it promotes succulent tissue growth in the cell walls of the plant that makes it more susceptible to disease. You should also regularly trim and prune the old and diseased roots to prevent spreading the infection to other nearby plants.

When pruning, make sure you use the best pruning shears, that gives you the cleaner cut and prevents injury to the plants that could facilitate the disease to spread in the plant. Proper pruning helps the plant to improve its structure and encourages air circulation and light penetration.

Always sterilize the pruning tools between cuts to prevent transmitting disease to other healthy plants. You should safely dispose of the diseased plant or stem and don’t compost it.


Top 5 Killing disease and how to prevent them

1 – Leaf Blight

Leaf blight (Drepanopeziza Rbis) is a widespread disease that affects leaves and fruits. These are also known as leaf spot. You can identify it by looking at the leaves that may have small irregular spots both on tops and undersides of leaves.

On fruits, it appears in specks. This is a fungal disease, and if not controlled on time, it continues to spread to neighboring leaves. At its peak, the spots on the leaves and fruits become dark brown, grow larger and coalesce.

At severe infestation, most of the leaves turn yellow and fall off. It may cause the entire plant to become defoliate and drop any existing fruits hanging on the plant.


You should safely remove and destroy the infected leaves and fruits to stop the spread. Don’t water the plant overhead as it makes conditions favorable for the spread of the disease. Prune the plant, so there is better air circulation, and the plant stem is free of the illness.

You can also apply Bordeaux mixture, copper, or sulfur fungicides to infected disease in every ten to twenty days.

2 – Apple Scab

If you have an apple tree in your garden, then you may have seen your fruit gets infected by Apple scab at some point. The Apple Scab (Ventura Inaequalis) affects the leave and fruit of the apple tree.

The typical symptom of apple scab is the gray patches on the fruit. Interestingly, it does not affect the fruit quality, but you can’t eat the infected part and looks unhealthy. If you sell apples, then it seems cosmetically rough, and you may not be able to get the best price on your product.

The apple scab is a fungal disease that overwinters in fallen leaves and fruit, which release spores in spring to infect new leaves and fruit. It’s widespread in areas that are more humid and wet.


Early prevention is essential as once infected, and gray patches appear on the leaves and fruit, the controlling is difficult, and spraying won’t give many results either. 

As a preventive measure, you can use fungicide during the cold and wet seasons. The fungus does not fare well in the hot season, so you don’t need to spray fungicide during summer.

The fungicides with sulfur concentration are very useful in controlling apple scabs. You can also check out fungicides from your local garden store that has a high sulfur concentration in it.

3 – Fireblight

Fireblight (Erwinia amylovora) affects edible and fruit plants such as apple, pear, and raspberries. It affects several parts of the plant, but most prominently it affects, flowers, leaves, stems, branches, and trunks of the plant.

You can know if your plant is affected by Fireblight by paying close attention to the flowers on the plant. When infected, the flowers first appear water-soaked and that later turns brown. The leaves on the plant turn brown and shrivel but won’t fall off the stem.

The leaves appear twisted and brown like scorched by fire and hence the name Fireblight disease. The infected branches of the tree form a curve at the tip that is also known as shepherd’s crook.

Unlike the above disease that is fungal, the Fireblight is a bacterial disease that spread through pollinating insects, overhead irrigation, and rain. 

The infection starts from the flower, that spread to the fruit and stem of the plant. The infected flower releases a sticky substance that attracts insects and flies. It then sticks to their feet and wings and uses it as a carrier to spread to the other plants.


One of the best ways to prevent Fireblight is to grow a plant that is resistant to it. Newer Apple breeds are raised to become fireblight resistance. You can check the new plant description that may mention the disease it can resist.

Also, be careful when pruning or trimming the branches of the plant. You should disinfect pruning tools after every cut, especially when you know the plant is infected. 

Avoid pruning late summer or fall to prevent winter injury to the plant. The plant needs to harden off in preparation for cold temperatures. You should also reduce or stop fertilization during this period.

When you are pruning, cut the step that is at least 30 cm below the point of infection and safely dispose of the infected plant material. In case of severe infestation, you can use pesticide applications such as Blightban and Serenade.

4 – Powdery Mildew

Powdery mildew affects many plants, especially fruit plants such as plum, raspberry, strawberry, cherry, and pear. It affects stems, foliage, and fruits.

When the plant is infected with powdery mildew, multiple small white talcum powder-like sports appear on the foliage. Most often, the affected foliage turns brown and dry up. The white, powdery coating develops little brown to black dots on the fruits.

The infected fruit may appear scarred and show brown russeting or remain discolored. The plant looks unhealthy and looks terrible in shape.

The powdery mildew is unharmful to the plant at a mild infection stage. It’s a fungal disease found on almost all fruit plants. The severe infestation of powdery mildew can severely stunt the plant and become worse when the outdoor temperature is high such as in summer.


The best prevention is to use plant variety that is an inherent resistance to powdery mildew. You should also prune the plant to promote good air circulation and sunlight penetration. You should avoid planting too close and avoid shade. Also, avoid using fertilizers that are high in nitrogen.

When watering the plant, try not to wet the foliage. Powdery mildew gets worse when the weather is humid and excessive moisture on the foliage.

You can also apply sulfur with Bacillus subtillis formulation. Depending on the area you live in, a licensed applicator can only buy it. Meanwhile, you can wash infested foliage with water to prevent the spread. Be careful as the fungal spores are unable to germinate in the presence of water, but it may cause the plant to become vulnerable to other diseases.

5 – Phytophthora rots

Phytophthora rots affect most fruits and several woody plants. It affects apple, cherries, strawberries, and raspberries the most. On a positive note, the plum and pears have some resistance to this type of disease.

The Phytophthora rots affect the roots and shoots of the plant. If not controlled timely, the weak root causes the plant to fall and die.

The above plants are more susceptible to Phytophthora rots during the spring and fall. This is due to the wetter condition of the summer. In spring, the buds may grow healthy, and fruitation may occur. But as the roots start to rot, all growth collapse and the entire plant dies.

The bark of the infected plant may look purplish, and the foliage breaks very quickly due to the rotted root system. People often get it confused with Fireblight.  

The main distinction between Phytophthora and Fireblight is the growth pattern. Fireblight starts on tips of branches and spreads downward, whereas Phytophthora causes the sudden collapse of the entire plant.

A mild Phytophthora infestation may cause partial damage to the roots and may cause yellowing of leaves with red or purple tint late in the season.


This fungal-like disease in most common in wet soil and tend to be more common in young plants. Unfortunately, once infected, there is no cure for Phytophthora. Prevention is the best key, and you have to select a well-drained site before planting and not to overwater the area.

Also, pay attention when buying the plant. Choose healthy plants that are free from any disease. Be careful when tilling or cultivating the plant as the damage to the roots means more likelihood of plant to get diseased.

If the plant has died from Phytophthora, avoid replanting another fruiting plant in that area.


The plant disease can ruin your garden, and all the years of hard work in planting are caring in your garden. It takes little effort to prevent the infection to the plant. 

But all is not lost if you find the plant to be infected. In most fungal infections, you can use fungicides such as Bordeaux mixture, copper, or sulfur compositions that are less toxic to humans than other fungicides.

Overall, proper planning to counter any type of disease will result in a healthy plant in the garden and nutritious and healthy fruits.

Author Bio:

Mark is an avid gardener and content manager at He loves all things related to gardening and home decorations. He believes in healthy living and healthy eating and grows his own vegetables and fruits in his backyard. He writes about everything from the gardening to landscaping.

Related Articles