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What Do You Need to Know About Indoor Plant Diseases-Part IV

It’s always a pleasure to share these useful information about indoor plant diseases with you. In this blog, we’re going to introduce some more plant diseases, for instance, Sooty Mold (Ascomycetes) and Viral Diseases. Problems are not terrible. What matters is how to solve them. Let’s check them out!

Sooty Mold (Ascomycetes)

Members of genera Cladosporium and Alternaria are the main causal agents of sooty mold. These fungi usually invade after aphids, whiteflies, mealybugs or other honeydew-producing insects have already occupied the plant. The sticky, sugary substance these insects leave on foliage and leaf axils is very attractive to sooty molds. All that sugar is a very rich source of energy, and few can resist such a luxurious meal.

It is very easy to identify sooty molds, as they cause typical symptoms on leaves – black, powdery spots of mycelium that make the leaves look charred. These fungi are a nuisance if present sparsely, as they do little to no harm to plants. However, if the plants are heavily infested with honeydew-producing insects, sooty molds can cover the entire leaf surface and reduce its photosynthetic activity. Along with the sucking activity of the pests, it contributes to the further decline of plants.

Viral Diseases

Considering viruses are not active outside a living host, they are usually brought into the grow room with the contaminated planting material. Another way plants can get infected with viruses is with the help of their insect vectors. Some species of sucking insects help these simple organisms to reach their primary host by carrying them inside their mouth or saliva. When these insects suck the juices of an infected plant, they also consume the viral particles. When they move onto the next victim, they will release a bit of their saliva along with the viral particles before beginning to feast, thus infecting the plant.


Different plant viruses can cause different symptoms, but the most common ones include:

  • Leaf yellowing
  • Mosaic-like or stripey spotting on leaves or/and fruits
  • Leaf curling
  • Abnormal growth of leaves, flowers, and fruits
  • Stunted growth

How severe can the symptoms be? Well, it depends on multiple factors. These include the strain of the virus(es), environmental conditions, age, stage of development and specific species of the host plant. Symptomatic plants usually carry a couple of different viral strains, because these microscopic troublemakers often occur in mixed infections. The most tell-tale signs of a viral infection are mosaic-like spots on leaves and abnormal growth of buds and fruits.

Viral diseases cause very severe yield loss (up to 100%) when the infection occurs early, in young plants. Unfortunately, there are still no viable remedies for plant viruses. If you find any symptomatic plants in your garden, dispose of them and the substrate immediately.

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