Common Plant Ailments – Treatments and Solutions

Last Updated on June 12, 2023 by Real Men Sow

Plant diseases affect plants of all kinds, in gardens, greenhouses, farms, and forests. The life cycle of most plant pathogens is complex and can be hard to track. Discover how to identify common plant ailments and choose the best treatment method.

Black Spot 

Although the black spot is most commonly found in roses, it can also be found on ornamental and garden plants. This fungal common plant ailment results in black spots on the upper leaves. Infected leaves usually fall first on the lower side. Infected leaves can turn yellow and eventually fall off plants when they are infected. Black spots can occur when the leaves are exposed to water for long periods or for more than 6 hours. The black spot spores can overwinter in fallen leaves.

Tips to Control Black Spots in Leaves

  • Make sure to plant in well-draining soil. Regularly feeding your plants organic fertilizer will help to keep them healthy. This will prevent the spread of fungal diseases.
  • The fungus spores can overwinter in plant debris. Take out dead leaves and infected canes and dispose of them in the trash. Do not add to the compost pile.
  • After each use, disinfect your pruners using a household disinfectant. Straight from the bottle, you can use ethanol and isopropyl alcohol.
  • Avoid putting water on the leaves as water spreads fungal spores. Water should be applied directly to the roots when you water. To water plants that are susceptible to this common plant ailment, use a soaker hose.

Other Leaf Spots

You can find fungal leaves spot common plant ailments indoors and outdoors on houseplants. This can occur in warm and wet environments. As the disease progresses, fungal spots become large enough that they touch one another. The leaf surface becomes more like a blotch than a spot. Defoliation can occur from the leaf spots. The same steps are used to treat black spots.

Powdery Mildew  

Powdery mildew can affect many plants and flowers in our landscape, as well as vegetables, fruits, and vegetables. It is easy to spot powdery mildew. The white powdery substance will appear on infected plants. It is most noticeable on the upper leaf surfaces. However, it can also be visible on stems, flower buds, and fruit. Low soil moisture and high humidity on the plant’s upper surfaces are the best conditions for this fungus. This fungus is more likely to affect plants in shaded areas than those that are in direct sunlight.

Powdery Mildew: Tips to Control it

  • Before you purchase plants inspect the plants for mildew or insects from a greenhouse,
  • Powdery mildew will return to the leaves if it isn’t removed by wiping them off.
  • All infected material should be removed as spores can overwinter in the debris. Remove infected parts of plants.
  • Do not place the debris in the soil.
  • Plants should be spaced apart enough to improve air circulation and decrease humidity.

Downy Mildew

It is important to know the differences between downy and powdery mildews. Powdery mildews can be considered fungal pathogens. They produce a white powdery substance that appears on the upper leaves. Downy mildews are more closely related to algae and produce grayish fuzzy-looking spores at the lower surface of the leaves. Look for yellow or pale green spots on older leaves to identify downy mildew. 

The fungus will produce a downy substance that is white to grayish in color on the lower surfaces. Cool, humid weather is the best time to get downy mildew. This can happen in late spring or early fall. Temperatures below 65 degrees F and high relative humidity are favorable for spore production.

Downy Mildew Treatment Tips

  • Water is essential for downy mildew to thrive and spread. This common plain ailment can’t spread if there isn’t enough water on the leaves. As much water as possible should be kept off the leaves.
  • This common plant ailment can overwinter on plant debris so make sure you clean up after your plants in the fall.
  • Some fungicides that are used to treat powdery mildew won’t work with downy mildew. The fungicide Earth’s Ally will treat both powdery mildew and downy mildew.


Plant blight can be a serious common plant ailment. Do you remember the potato famine of 1840? One million people died as a result. Blight affects more than just potatoes. It also affects tomatoes and other plants. Blight is a fungal infection that is spread by spores from the wind. The spores can quickly spread to large areas, spreading the disease rapidly. Warm, humid conditions are necessary for blight to spread, particularly if temperatures rise above 50 degrees F two days consecutively and the humidity is above 90% for at least 11 hours. No cure exists. Prevention is the only way to save your life.

Tips to Prevent Blight

  • Plant potatoes early if you want to avoid blight.
  • Plant-resistant varieties: Sarpo Axona and Sarpo Mira are two varieties with good resistance. Practice good garden hygiene.
  • Remove any infected parts of blight-infected plants. Make sure to remove all fallen leaves and diseased plants from the area. Don’t add to your compost pile.


An open wound infected with fungal or bacterial pathogens is often a sign of a canker. While some cankers can be benign, others can prove fatal. Canker is most common in woody landscape plants. Sunken, swollen, or cracked areas on the trunk, limbs, or stems can be signs of canker. Cankers can cause branches to girdle and even kill the plant. Cankers are more common in stressed plants that have been affected by cold, insects, or drought. Rodents can also spread pathogens.

Tips to Control Canker in Plants

  • Dry weather is the best time to remove diseased parts.
  • When possible, grow resistant varieties
  • Avoid overwatering or overcrowding. Also, avoid mechanical injuries such as lawn mower damage.
  • To prevent sunscald, wrap young trees that have just been planted. If the trunks were shaded and then transplanted to sunnier areas, sunscald can form dead patches on the trunks and limbs.
  • Planting in good soil and meeting nutritional needs will help keep your plants healthy.

How to Control Plant Fungus and Common Plant Ailments

Before you plant, make sure the soil is well-drained and has plenty of organic matter. If necessary, raise the beds and then fill them with a commercial potting mixture that drains well. Rotting can be caused by soils that retain too much water. Avoid putting water on the leaves. Water the roots by hand or using a soaker hose. To keep your plants in top condition, fertilize as needed.

Choosing Resistant Varieties

When possible, choose resistant varieties. To improve air circulation, prune or stake your plants. You can place plants in containers away from areas that don’t receive enough air circulation. To prevent the disease from spreading, remove infected materials. Take out infected plants and put them in the trash.


The plants should be watered in the morning so they can dry out and not get water on their leaves. If you have downy mildew, water later in the morning as it prefers morning moisture. Avoid getting water on the leaves. A soaker hose will help to keep water at the root and prevent the spores from spreading.

Inspect Plants Before Purchasing

Before purchasing plants from your local greenhouse, inspect them for pests and disease symptoms. After cutting out diseased parts of plants, disinfect pruners. Buy a hand lens. A hand lens with a 10x magnification is an excellent way to spot fungus or insect problems. A hand lens can also be used to view things in nature that are hard to see with your naked eye.

Make Use of Fungicides

Use a fungicide to protect all parts of your plants from common plant ailments. An OMRI Listed(r), contact fungicide and bactericide that is Earth-friendly, Plant Disease Control, can be used on both houseplants as well as organic gardens. 

Real Men Sow
Real Men Sow

Hello, I’m Pete and I’m currently based in the west of Scotland, in a small place called Rosneath, where I’m exploring my garden adventures. I personally started gardening around 6 years ago and initially, I started out by growing my favorite fruits and berries, such as strawberries, Raspberries & Gooseberries. Since then I’ve added a lot of vegetables and working closely with my neighbor, it’s been a lot of fun.