Sclerotinia or white mold, the great enemy of plants

Today, we are going to introduce ourselves to the world of plant diseases and, above all, those caused by fungi. In today’s article, we will talk about the genus Sclerotinia and its main representatives. An ascomycete fungus that is present in many seedlings and causes stem and pod rot. Let’s get to know it.


As an initial curiosity to tell you that it is necrotrophic , that is, first they kill cells and then they absorb their nutrients. They still continue to feed on the host despite having killed it.

This ability is typical of some fungi that will also sound like fusarium, cankers, blights and other rottenness.

Sclerotinia sclerotiorum cycle
Source: serida


They have a great capacity for survival and they do it in different places. The most common area is the ground, although it can also be present in plant debris or weeds.

The optimum temperature for the dissemination of its ascospores is between 20 and 25 ºC. In addition, the environment has to conserve enough humidity, either due to continuous irrigation or precipitation.

If conditions are good, the Sclerotinia fungus  can survive in soil for up to 10 years. eye!


The damages that Sclerotinia produces are various. On the one hand, the seedlings produce the so  called  damping-off that we will explain later what it consists of.

A watery-looking white rot appears on the plant that eventually dries up. At that moment is when a cottony mycelium forms like the one you can see in the following image.

White mycelium of Sclerotinia sclerotiorum
Photo : Jymm

On the leaves, burns occur at the ends, with a greater incidence at the tips of the leaves. The normal thing is that the infection begins from the ground, and ascends until the aerial part. When it is in the stem, what we are going to tell next is produced.


This term that translated into Spanish would be something like fungal wilting, they  appear when in the middle there are high humidity and mild temperatures.

When the fungus is located in the seed, the fungus infects quickly and can prevent its germination. There are other times that the seedling manages to develop very weakly and ends up dying due to the collapse of the vascular vessels.

However, damping-off is not exclusive to the Sclerotinia genus  , since it can also be performed by the following fungi and some others:

  • Phytophthora
  • Rhizoctonia solani
  • Botrytis  (gray rot)
  • Pythium


White mold has the ability to attack a large number of plants, regardless of whether they are vegetables, fruits or ornamentals. Cases have been seen in which some woody species have had Scleorithin , although this infection is limited to the young and green parts of the plant.

Nor does it make a distinction according to the phenological state of the plant or its growth stage. Sclerotinia infection can occur both in the seed stage, seedlings (open air or seedbed), mature and high-growth plants and even on the fruits already harvested.


Among the chemical products that can be used there are different active ingredients. There are some that are also of natural origin and are based on the use of  Bacillus subtilis,  a Gram positive bacterium we can find commonly in the soil.

The applications of  Bacillus subtilis as “active matter” vary according to the crop, but are usually between 2.5 and 4 kg / ha.

As a chemical product , a very effective remedy against  Sclerotinia  is the use of fenhexamide as active material, a component belonging to the hydroxyanilide family.

It should be noted that this product has the category (N), dangerous for the environment.


As always, the horticulturist can perform some tasks to reduce the possibility that his crops will be affected by this phytopathogenic fungus. On the one hand, there would be the ideal selection of seeds that are healthy and perform a cleaning and disinfection of it.

The solarization , a technique already discussed in Gardenprue can contribute to disinfect soils harboring any kind of  Sclerotinia.

On the other hand, here we also give importance to the rotation of crops ,  the greater separation of the plants if the environment is very humid and the ideal conditions are given for their appearance (to achieve greater aeration between plants), and the turning of the soil to provide it with greater lightness and less retention and greater drainage.

A widely used and practical task is to avoid weeds that may harbor this opportunistic fungus, while waiting for wounds or weaknesses to appear in the plant and infect them. If the soil is clean, the distance between plants is appropriate and there are no weeds involved, the chances of finding white mold are reduced.

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