What Are Leaf Spots and How Do They Affect Your Leaves

April 19, 2022 Published by Leave your thoughts

What are leafs spots?

Leaf spot is a term used to describe many diseases affecting the leaves of shade and ornamental trees. Several leaf spot diseases occur on a wide range of plants and shrubs.

What causes leaf spots? 

Many leaf spot diseases have similar biology and therefore very similar management options. Leaf spots are often caused by fungi, though some are caused by bacteria. In other instances, insects cause damage that looks like leaf spot disease. Leaf spots are common on trees and normally do not need spraying. Leaf spots can result in some defoliation of trees. A full-grown plant may endure complete defoliation. However, newly or small planted trees that become defoliated are at risk of becoming damaged till they get established.

Bacterial leaf spots and fungal leaf spots

Bacterial leaf spot infects some annual and perennial flowering plants such as geraniums, purple coneflowers, zinnias and black-eyed Susan. On the other hand, fungal leaf spot infects poplar and aspen trees. 

Both leaf spot diseases are most active in warm temperatures and humid conditions. During summer, if you use overhead sprinklers to water the plants, the moisture may be adequate for infection.

Leaf spots symptoms and diagnosis

  • The main symptom of this disease is black or brown water-soaked spots on leaves. However, dark margins or concentric rings are often present. These spots vary in color and size depending on the affected plant, the plant’s stage of development, and the organism involved. Fungi may appear as black dots in either the spots, rings, or a cluster. With time, the spots combine and enlarge, forming blotches. Angular or blotched spots are generally known as anthracnose. Leaves may turn yellowish and fall prematurely.

Is there a way to prevent leaf spots?

  • Live with the disease. Most plants endure leaf spots with no or little damage. Trees that are affected early re-leaf and may not be affected later. It is only when defoliation happens more than three years consecutively, that most mature plants will be significantly affected. Remove dead twigs and infected leaves. Removing and disposing of infected leaves can assist in controlling the spread of disease to the non-infected leaves. This is not a cure but reduces infection.
  • Replace severely infected plants: Though a radical measure, many people find it ideal to replace plants that are continually affected by leaf spot disease.
  • Keep foliage dry: You can achieve this by avoiding overhead watering. Use water early in the day or soaker hoses so that the leaves can dry before night. Watering might also spread the leaf spot disease by splashing. Pruning allows good air circulation and minimizes crowding, helping keep the leaves dry.
  • Keep plants healthy: Abundant, young growth is susceptible to attack by insects and diseases. Overuse of fertilizer causes an abundance of growth. Thus, you should maintain them in good health since most can tolerate defoliation. 
  • Use fungicides if need be: In case of severe infection and when the value and size of plants allow, apply fungicides. Sprays rarely cure infected leaves. Thus, once the leaves are damaged, spraying might not assist.

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