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Past Articles Library | Plant Diseases & Control | Plant Diseases of Pansies



Pansies are a beautiful addition to any spring and early fall plantings. While they are easy to grow and maintain they do have a few plant diseases.  Below are a few of the most common plant diseases that one can expect to find when one grows pansies. 

Anthracnose

Anthracnose is caused by the fungus Colletotrichum gloeosporioide.  This fungus first appears as small, white spots that are trimmed with a black border.  While these spots can appear on any leaf, you can find an increase number of these spots on the top of the lower leaves. 

When environmental conditions are humid and wet, the white spots will develop little, black dots.  These are the fungal spores, which will spread when water dislodges them from the leaf.  Once they have been dislodged, they will spread to uninfected leaves and symptoms will appear in one week.

While there are chemical solutions to this problem, the best approach is to remove affected leaves.  If there are too many leaves to remove and have anything left then dispose of in the trash. 

Cercopora Leaf Spot

This leaf spot is caused by the fungus Cercospora violae.  If you are going to get this fungus, you can expect to see ii either in the early spring and/or early fall.  This fungus will appear as a dark gray spot that is about one-fourth of an inch in diameter.  The spot itself will have a raised texture and appear on the lower leaves.

Cercopora leaf spot will appear when conditions are humid and leaves are left wet.  Once you have this fungus, it can spread by wind or water droplets.  While wind cannot be controlled, how you water can.  To prevent this fungus problem, water in the morning.  This will give the sun time to dry the leaves.  Also, rotate where the pansies are planted in the landscape.

  If you do find that you have this fungal issue starting, pick off the affected leaves.  On the other hand, if the fungus is widespread, just throw away the plant.

Powdery Mildew

While pansies do suffer from powdery mildew, it is normally not a problem.  Why is this you may ask? Well the answer is simple, once you see the evidence of powdery mildew; it is time to replace the plants with something else. 

How do you know if you have it?  The fungus will appear in the spring or fall when temperatures are drastically going up and down and humidity is high.  Powdery mildew will appear as very small, white patches that will increase in size until the whole leaf is covered.  Once that happens, the leaf will die and fall off.

Bortrytis Blight

This pansy disease is caused by a fungus called Bortrytis cinerea.  This fungus appears when the outside temperatures are in the low 50s to upper 70s.  Combined with the temperatures, the environment also needs to be wet and humid. 

You can tell if you have this fungus by taking a look at the flowers and their stems.  Bortrytis blight will appear as very small, brown spots on flowers and flower stems.  If the humidity and rain continue, the spots will turn dark gray and develop spider web like growths.  This develops when the fungus is maturing and producing spores.  Once this happens, the spores will be transferred to healthy blooms and flower stems by the wind and water droplets.

One you have discovered this fungus; pull up the plants and dispose of in the trash. 

While one cannot control the outdoor environment, there are a few things a gardener can do to reduce the chances of developing this problem.  One is to space the plants farther apart.  This will increase the amount of air that can get around the plants and in doing so drying things out a bit.  The second technique one can use is to only water in the morning.  This gives the plant material plenty of time to dry out before the sun goes down.

Myrothecium Crown Rot

The fungus that is responsible for this rot is Myrothecium roridum.  As the name indicates, this fungus attacks the crown of the plant when temperatures are warm and rain has been frequent.  It appears when the crown of the plant has turned brown.  Once that happens, the plant will wilt and die.  Prior to this, little white and black dots will appear.  These are the spores of the fungus, which are spread through water movement. 

To prevent from developing this problem, do not plant pansies in areas that remain wet, water only when needed and in the morning. 

What do you do if you already have the fungus?  Throw the plants away that are showing symptoms of this plant disease.

Black Root Rot

This is a soil borne fungus called Thielaviopsis basicola.  It thrives in alkaline soils that have a pH between 6.5 and 8.  It also requires cool temperatures and wet soils. 

To see if you have this root rot, you will first need to take a look at the roots.  In the beginning, you should see roots that have black spots and/or bands.  The root tips may also be black.  As the disease progresses, it may be harder to tell if it is black root rot since the roots will turn brown, which is a symptom of many different root rots.

To prevent this, take a soil test before planting your pansies.  Also, rotate your plant material and never place pansies in areas that have history of being wet.  Finally, monitor soil moisture and only water as needed and in the morning.

If you find that you have black root rot, pull up the plant and remove any soil associated with the plant.  Dispose of in the trash. 

Pythium Crown and Root Rot

This is another soil borne fungus that thrives in wet soils.  Plants can also become more susceptible to this fungus if they have been stressed and/or over fertilized.   If your pansies are suffering from this fungus, they will have water-soaked sores on their stems that are along the soil line.  The roots of these plants will be brown.  The plant will begin to show signs of rot, which consists of squishy roots, yellowing foliage and finally wilt.  After these symptoms have appeared, the plant will die. 

Water transports this fungus.  To prevent this, monitor soil moisture and throw affected plant material away.

Phytophthora Aerial Blight, Crown Rot, and Root Rot

Phytophthora nicotiana is a soil borne fungus that causes several rots and blight.  Rots are caused when environmental conditions are too wet and plants are weakened by drought and/or excessive feeding.  Blight, on the other hand, occurs when temperatures reach 75 to 85 degrees Fahrenheit, high humidity is present and the leaves are left wet.  Light brown spots that are filled with water will appear on leaves and their stems and/or the stems will be girdled with a light brown wound.  Either one of these will cause the affect plant material to die. 

If you already have this problem in your pansies, remove them immediately.  Since this plant disease spreads so easily, take a bag with you and dispose of in the bag as soon as the plant has been pulled up.  This will prevent the disease from spreading throughout the garden.

To prevent this problem, improve the drainage of the garden and only water when needed.

While pansies are easy to grow, as you can see many of these plant diseases can be avoided by proper drainage and watering practices.










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