What environmental condition promotes the growth of brown rot?

The growth of brown rot is significantly influenced by environmental conditions, particularly moisture and temperature. Brown rot fungi thrive in wet and humid conditions because moisture is essential for their development and reproduction. These fungi break down the cellulose in wood, which is most effectively achieved when the wood is saturated with water.

In humid conditions, the wood absorbs enough moisture, creating a favorable environment for the fungi to grow and proliferate. A relative humidity level above 20% is generally conducive for brown rot because it allows the spores to germinate and develop into mycelium, which is the vegetative part of the fungus.

On the other hand, cold and dry conditions tend to inhibit fungal growth, as lower temperatures slow down metabolic processes, and lack of moisture prevents the necessary conditions for growth. Warm and dry conditions also do not support brown rot, as the absence of moisture makes it difficult for the fungi to establish themselves. Cool and humid conditions may promote the growth of some fungi, but brown rot specifically favors warmer temperatures combined with high humidity.

Thus, the correct answer highlights the critical role that wet and humid conditions play in supporting the growth of brown rot.