Fungal Diseases

The life cycle for fungal pathogens like Dry Bubble, Trichoderma, and Cobweb is simple, Figure 1. Spores germinate into mycelium, which forms structures that produce spores. In a petri dish culture that may take less than a week; in compost or casing, it is probably pretty much the same. However, other factors like pH, moisture, and nutrient availability may influence this life cycle timing. Much of that, however, is unknown for these pathogens.

Looking at the disease cycle in mushroom cultivation, we know a relationship exists between spore load, time of infection, and symptoms or signs of disease development. Let’s look at the three most common fungal diseases and what we know about these relationships.

Dry Bubble, caused by Lecanicillium, or Verticillium has symptoms that develop based on spore load and timing of infection. Spores coming in contact with a fully colonized spawn run don’t germinate well and little disease will develop. It may be possible that spores landing on the substrate the day before or the day of casing could cause an early disease development. Spores in contact with the rhizomorphs in the casing will easily germinate. How fast they germinate, and the vegetative mycelium growth may be influenced by casing pH, moisture, relative humidity, and temperature.

It is unknown what the optimum conditions are but in general the warmer the conditions the faster the growth and the shorter time from spore to symptom development. In general, spore to symptom takes about seven to 14 days depending on the above factors. However, when Dry Bubble mycelium is in contact with mushroom pins,metabolites are produced that degrade mushroom tissue. This process seems quick, perhaps hours to a day or two.

Read the full factsheet here.

Written by: David M. Beyer