6. Oyster Mushroom Culture Pests

Here I will briefly summarize some of the most important things to keep in mind when starting the oyster mushroom cultivation process:

• Excessive humidity damages and undermines the mushroom mycelium.
• Heat treatment failure leads to substrate infection with competing molds, bacteria or insects. 
• Low intensity light or the lack of light in the grow room during fruitbody formation results in inhibition of fungal growth and development
• Excessive temperature (grater than 35 °C / 95 F) inhibits and destroys mycelium
• Excessive concentration of carbon dioxide in the grow room inhibits the development of mycelium
• Substrate inoculation with a low quantity of mycelium increases the risk of infection by competing organisms for the same nutrients, increases the incubation time, and decreases the mushroom crop. 

Pests may be divided into two categories: pathogens and competitors. Pathogens are fewer than competitors and have a devastating effect on the mushroom culture. They are: molds, bacteria, viruses, or insects. Competitors refer to those pests that cause competition with the inoculated oyster mushrooms mycelium for the same type of nutrients found in the compost. However, not all contaminants are considered pests. There are certain bacteria or fungi that are rather important for oyster mushroom mycelium development and have a direct effect on the mushroom crop. Such organisms belong to the following genera: Humicola, Torula, Actinomyces, Streptomyces, and some species of Pseudomonas or Bacillus). For this reason it is recommended to pasteurized the substrate (80-85 °C / 176-185 F) and not to sterilize it. In addition, through sterilization the substrate is predisposed to infection at a higher rate through exposure to air. 

Here I will briefly present you some of the most common pests:

A. Trichoderma viridae (the green mold)
It is very common and appears as green masses of moldy areas infecting the substrate partly or integrally. It is characterized by a rapid growth and acts as a parasite on the oyster mushroom mycelium and may inhibit the occurence of mushoom pinheads or mushroom fruitbody development. It was shown that T. viridae prefers a more acidic substratum (4-6 pH) and this is also the reason why you should use gypsum in your substrate formula. Trichoderma spores stick to anything, therefore insects when occur may function as a contamination vector that can spread the local contamination to the whole mass of substratum.

Fig. 30. Trichoderma viride

(Photo credits: www. biogardenorganic.com) 

Note: Substratum contamination may occur also when using infected mushroom mycelium at inoculation. This is why, your mycelium should be bought from a clean source that you trust. 

Correct heat treatment of the substrate, clean grow room before incubation pahse, reduce moisture level in the grow room during incubation, reduce carbon dioxid level in the grow room by frequent ventilation (if possible), use clean tools, use gypsum at an optimal rate. 

Note: If Trichoderma occures in the substrate take the bag outside of the grow room and lower the substrate pH by adding baking soda or salt.

B. Contamination because of insects (nematods, flies, mites, etc)
Mainly the flies are insects able to invade the mushroom culture and infect it with various pathogens. They are attracted by the smell of the decomposing substrate. Flies are laying eggs near mycelium while hatched larvae consume it. 

What can you do against flies, nematods or mites?

• Add a mesh at each window, this will have good results in preventing flies entering the grow room;
• Use UV lights, the blue color will attract insects;
• Apply a proper heat treatment to the substrate (if not, possibly you will see mites walking in the substrate)
• Avoid excess moisture in the substrate (if not, you will see nematods developing in your substrate)
• Use clean tools during mushroom cultivation

Fig. 31. The common mushroom culture fly (Lycoriella spp.)
(Photo credits: www.google.com)

Fig. 32. Nematod
(Photo credits: www.google.com)

Fig. 33. Mites (Tyrophagus putrescentiae)
(Photo credits: www.google.com)  

C. Other mushroom species (e.g., Coprinus spp.)
This mushroom belongs to the family of Coprinaceae and is characterized by a characteristic outline with the cap when mature disolving and turning into a black ink. This mushroom may be quite often seen growing into the substrate destinated for oyster mushroom cultivation. The causes may be the lack of oxygen into the substratum due to the lack of porosity or lack of gypsum in the substrate. The latter situation rises the pH in the substratum offering ideal conditions for species of Coprinus to develop. 

Note: There are several species of Coprinus that may appear in the substratum: edible (C. comatus, C. atramentarius, etc) or non-edible (C. micaceus) or even toxic. If you encounter them in your substrate i highly recommend you the following: do not eat them!

Fig. 34. Coprinus spp. growing among Pleurotus fruitbodies(Photo credits: www.google.com)  

Few Words about Oyster Mushroom Production

On the market there are many excellent strains; however, is hard to know which one is the best as long as you do not make a mushroom strain evaluation. Productivity depends on a complex of factors (microclimate conditions, type of substrate used, mushroom species, strain, etc) some of them difficult to take into account. In a next course we intend to discuss in detail what factors influence productivity and how can they be controlled. 

Fig. 29.  Fruitbodies of Pleurotus eryngii (nameko)
(Photo credits: www.google.com)

What can you do with waste material used in mushroom production?
The remnants may be used for animal feed, as an organic fertilizer for soil or simply as fuel for fire. 

Find Out More!

1. Some of the Most Important Cultivated Oyster Mushroom Species
2. Preparing the Chamber and Tools Needed for Oyster Mushroom Cultivation

3. Compost Making for Oyster Mushrooms
4. Compost Heat Treatment and Inoculation
5. Incubation, Fruitbody Development and Harvest
6. Oyster Mushroom Culture Pests
7. How to Grow Oyster Mushrooms on Logs

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