Botrytis Blight: What Is It? How To Control Fungal Disease On Plants?

Botrytis blight is one of a variety of fungal plant diseases that attack many different kinds of plants. From African violets to garden veggies.

This fungus has a negative impact on all above-ground parts of affected plants including leaves, stems, buds, flowers, and fruit.

It is easy to confuse fungus botrytis with other types of fungal diseases because the damage that fungi of all sorts cause is quite similar.

Noble rot on grape with Botrytis

Additionally, there are many different species of botrytis such as botrytis cinerea and each of these species is made up of several different strains.

As with all fungi, the botrytis plant disease is most active and thrives best in damp conditions.

For this reason, it can be a real problem in a garden setting such as storage areas where nursery stock is kept for the winter.

Botrytis is also a real problem in greenhouse crops in the wintertime with high humid conditions but the temperatures dropping significantly during the night.

Overall cool temperatures may cause the growth of the fungal disease to slow down, but if there is moisture in the air disease development will continue to still spread even in cooler temperatures.

How Does Botrytis Blight Harm Plants?

You can expect botrytis infection on plant stock in temperatures ranging from 32° – 80° degrees Fahrenheit.

When the weather is very hot and dry, botrytis cannot spread.

Even so, spores can lie dormant on the soil surface and reactivate when the weather becomes damp and cool once more.

If no live plant material is available, botrytis can live quite handily on dead plants or on plant debris on the ground.

It’s easy for it to spread from there to live plant stems, leaves and even flower petals. Plants in a weakened condition are especially susceptible to attacks by botrytis.

Healthy plants that have been damaged or wounded are also susceptible to infection by botrytis blight.

This is why it’s important to only prune plants during dry weather and to apply an antifungal product to cuts on pruned plant parts.

Botrytis causes twig Blight on all parts of compromised plants. It also causes conditions such as:

  • Damping Off
  • Root rot
  • Gummosis
  • Fruit Rot
  • Stem lesions
  • Leaf spots
  • Stem cankers
  • Flower petals sticking together

How Does Botrytis Spread?

When any part of the plant is infected, botrytis spores will spread from the infected area to noninfected areas.

Additionally, spores may be spread from plant-to-plant through moisture and air currents of the wind.

Any time humidity levels rise or decrease rapidly, spores are released. Rain also stimulates spores to spread.

During times when relative humidity rises and the air is moving, turning the soil around infected plants can cause spores to be released and spread.

This is especially true if infected debris or groundcover is disturbed under conditions that allow spores to migrate easily.

Pest Management –  The Control Of Botrytis Infections?

Botrytis is a danger to all plants. There are no types of plants known to be resistant and botrytis is known to have excellent fungicide resistance.

The best way to control the spread of this ubiquitous fungus is to simply maintain environmental cultural practices and conditions that deter it.

This can be done by knowing and understanding the needs of all the plants in your care.

  • Avoid overhead watering entirely, and don’t work in your garden after rainfall as your presence may help spread botrytis spores.
  • Use ground watering (try soaker hoses) and avoid allowing water to splash up from the soil onto your plants.
  • Space plants to provide good air circulation and air flow.
  • Give plants the right amount of light.
  • Don’t use too many chemicals or prune excessively.
  • Avoid overwatering or leaving plants too dry.
  • Watch out for nutrient deficiencies and avoid using too much or too little fertilizer.

NOTE: Apply fungicides in advance of the botrytis disease as a protectant. The following fungicides are registered for use to control botrytis include copper, captan, chlorothalonil (Daconil), mancozeb, maneb, sulfur, and thiophanate methyl (Cleary 3336).

How Can You Tell If Your Plants Have Botrytis?

Plants infected with botrytis may develop a grayish web known as mycelium (a.k.a. gray mold).

When you see this on any part of any plant, prune away the damaged tissue.

For very heavy infestation, dispose of the plant altogether.

Wrap infected plant tissue in a plastic bag, seal it up and set it out with the trash. Do not compost plant matter infected with botrytis.

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