Top 5 Plant Killing Diseases and Protections

Plant diseases can ruin your day! If you have several ornamental or edible plants in your garden, it’s a good idea to have a strategy to identify plant diseases and take immediate action to stop the spread of the disease in infected plants.

Why Does the Garden Get Infected by Pests and Microbes?

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

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

  • Disease spreaders such as microbes or pests
  • Susceptible host plants
  • Favourable external conditions, such as weather, help 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.

Ways to Prevent Plant Diseases

Plant Young Plants

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

Consider Hybrid Plants

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

Don’t Over Fertilize

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.

Prune Your Plants

You should also regularly trim and prune old and diseased roots to prevent infection in other nearby plants. When pruning, make sure you use the best pruning shears that give you a cleaner cut and prevent 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.

Sterilize Your Pruning Tools

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 Plant Diseases and How to Prevent Them

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 defoliate and drop any existing fruits hanging on the plant.

Leaf Blight Prevention:

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 favourable for the spread of the disease. Prune the plant, so there is better air circulation, and the plant stem is free of illness.

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

Apple Scab

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

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

Apple Scab Prevention:

Early prevention is essential as once infected, when gray patches appear on the leaves and fruit, control 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 have a high sulfur concentration.


Fireblight (Erwinia amylovora) affects edible and fruit plants such as apples, pears, 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 spreads to the fruit and stem of the plant. The infected flower releases a sticky substance that attracts insects and flies. It then sticks to its feet and wings and uses it as a carrier to spread to the other plants.

Fireblight Prevention

One of the best ways to prevent Fireblight is to grow a plant that is resistant to it. Newer apple breeds are raised to be fireblight resistant. You can check the new plant’s 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 in 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 pruning, cut the step that is at least 30 cm below the point of infection and safely dispose of the infected plant material. In the case of severe infestation, you can use pesticide applications such as Blightban and Serenade.

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.

Powdery Mildew Prevention

The best prevention is to use plant varieties that are inherently resistant to powdery mildew. You should also prune the plant to promote good air circulation and sunlight penetration. Avoid planting to 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 there is 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.

Phytophthora rots

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

Phytophthora rots affect the roots and shoots of the plant. If not controlled in a timely manner, 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 collapses and the entire plant dies.

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

The main distinction between Phytophthora and Fireblight is the growth pattern. Fireblight starts on the 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.

Phytophthora Prevention

This fungal-like disease is most common in wet soil and tends 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 getting diseased.

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


Plant diseases can ruin your garden, and all those years of hard work in planting and caring for your garden. It takes little effort to prevent infection to the plant. Adequately pruned and thinned plants help slow the disease due to better air circulation and enhanced water evaporation.

But all is not lost if you find the plant to be infected. For 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 plant diseases 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 gardening to landscaping.

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