Potato Blight

For first-time farmers, it may be shocking to hear of a condition called blights that form on your crops. They are commonly seen on crops like homegrown potatoes and tomatoes, and while it can be annoying, this is a condition that can be avoided with proper crop care.

So, what causes these blights in potatoes, and how can you avoid them? Below, we will discuss how you can identify when blight is forming and how you can avoid potato blights.

What Does Blight Look Like on Potatoes?

Also known as a water mould, potato blights are commonly present during warm and humid weather. They appear in dark and almost black splotches around your crop’s leaf tips and edges before they spread toward the middle. Your potatoes will also appear to have black spots – almost like they are bruised.

What Causes Potato Blights?

As we have mentioned, the black splotches that you often see on potatoes are called potato blights. They are mainly caused by excessive moisture in your crops and are prevalent in crops around late summer when the weather becomes humid and warm.

The first signs of potato blights are often seen in the potato flowers or if your potatoes are above ground. You will notice the black spots growing by the tip of the leaves before spreading toward the middle and onto the body. White spores of fungus then appear around the underside of the infected leaves.

When left unattended, these spores get released into the wind which will affect the neighbouring crops and get into the soil of your plants. This causes the fungus to seep into the soil, infecting the potato tubers and the potatoes themselves.

Unfortunately, it may be too late to stop potato blights when the fungal spores have reached the tubers. This is as a reddish-brown rot will take place in your potatoes through the potato tubers, causing the black splotches to spread through and through in your crops.

How to Avoid Potato Blights

Now that you know how potato blights form, you may be wondering how you can prevent it from happening. Granted, the last thing you will want to experience when planting potatoes is to see your efforts wasted. Here are some simple steps you can take to avoid potato blights:

1. Frequently Rotate your Crops

Many first-time farmers may make the mistake of re-planting the same crops in the soil after a single harvest season. Unfortunately, this may result in a build-up of disease spores in the soil, which could affect your newer crops for the season.

Instead, do aim to frequently rotate your crops to deter diseases from building up. This allows you to identify the problematic areas of your soil and protects your crops from fungal infections.

2. Plant your Crops in a Breezy Spot!

When planting your crops, be sure to pick a breezy spot. This ensures that your soil will dry quickly after it rains, reducing the possibility of blights from forming.

Try to space out your plants to ensure that they have enough airflow between them, as this too can prevent the dreaded fungal blights.

3. Treat the Soil with Fungicide Before you Plant

There are a variety of fungicides that you can apply to your soil before planting your crops. This ensures your soil is ready for the next planting season while killing away any possible diseases. 

The fungicide should be applied before blights appear, especially during wet seasons in early January.

4. Remove Blight-infected Plants at First Sight

Should you notice a plant being infected by blight, you should immediately remove it from your line of crops. This helps avoid the spread of the fungal spore to your other plants and the soil. 

The earlier you remove these blight-infected plants, the higher your chances of reducing blight in your other crops.

5. Plant Blight-Resistant Potatoes

Some potato variants are known to be more blight-resistant than others. Of course, they may vary depending on the type of potato harvest you prefer. Early potatoes like the Orla and Carolus or maincrop potatoes such as Sarpo Mira and Valor are great selections for blight-resistant potatoes.

Be sure to only purchase healthy and disease-free seed potatoes. Buying your potato seeds from a reputable supplier also ensures you will plant blight-free crops for the season. If possible, you will want to plant and harvest your potatoes before the blight season arrives – typically before late summer.

Can You Eat Potatoes with Blight?

Aside from the unsightly feature of potatoes with blights, many people may wonder if they can still be eaten once the affected areas have been removed. Well, although there are currently no studies that show the side effects of blights when consumed, some food specialists have advised against eating potatoes with blight.

This is because potatoes with blights may taste bitter, altering the taste of your dishes if you are using it in cooking. There may also be other microorganisms present in these potatoes, making them harmful for consumption or to be used in cooking and storing.

While some home cooks have recommended removing the blight and using only the non-infected parts, there is no guarantee that the potatoes are safe to be eaten. This is also why potatoes with blights are not recommended for storage, as they may infect non-blighted potatoes.


As you can see, the next time you are looking to plant potatoes as a crop of choice, blights should be something you are looking out for. To make it simple to identify what blight looks like on potatoes, then you will want to check on the tip of the leaves of your potato flowers.

You can easily avoid blights from forming on your potatoes by planning your crop plantation area properly and by providing ample space between your plants. Ensure that the soil is not overly wet or dry as these too can cause blights from happening. Finally, it may also be a good idea to treat your soil with a fungicide to avoid blights from happening altogether.

If you are not sure how to grow potatoes, you can check that here and if you are already growing potatoes, you can find out when is best to harvest them here!

Garden Doctor Trev

Garden Doctor Tips

“Prepare your bed with some well-rotted organic matter and some fungicide to prevent Potato blight!”

“If you have space, get in the habit of rotating your vegetables to prevent the build-up of diseases in the soil!”

“If you are really worried about your potatoes getting blight, Orla potatoes are a great variety to grow!”

“If you discover potato blight, destroy the plants and tubers – Do Not add them to your compost bin!”

Frequently Asked Questions

Can you eat potatoes with blight?

Although there are no documented cases of anyone being ill from eating potatoes with blight, (most likely because people are not daft enough to eat it) it is not recommended.

Blight is a fungal infection, and we recommend that you destroy the whole crop if you get an infection!

What are the signs of potato blight?

The first signs of potato blight are recognized by the colour of the leaves. The tips and edges of the leaves will start off with small, almost black splotches and the splotches will begin to spread towards the middle of the leaves and then the stem.

If the blight reaches the soil and the tubers, it is recommended that you destroy the crop.

What can I spray on potatoes for blight?

There is no known cure for potato blight so there is nothing that can be sprayed onto plants that have been infected. As soon as you notice the tell-tale signs of blight, cut the stems above ground level, and destroy the plants to prevent the spores from getting into the soil.

Immediately lift tubers if there are any and if they are unaffected, they can be eaten. If they have been infected, the potatoes should be destroyed too.

Is the gas emitted from rotten potatoes really dangerous?

The gas created by the decay of organic matter can be extremely harmful and even fatal if inhaled in large quantities. Potatoes emit a type of gaseous compound that may lead to a variety of health problems.

What health problems are associated with inhaling the gas from rotten potatoes?

Health problems associated with inhaling noxious gasses are things such as difficulty breathing, irritated airways or inflammation in your lungs tissues (alveolar cells), bronchitis or asthma attacks due to an allergic reaction – all very serious conditions that require medical attention right away!

About Me

Hi, I’m Trev and I’ve been growing things since I can remember. When I was younger, I grew up on a farm, so I have always been around plants and animals. After studying horticulture at university, I decided to start my own nursery which I have run now for 25 years. In my spare time, I run this website – which is a resource for people who want to learn more about their gardens.

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