Which of the following can be a visible symptom of lichen growth?

The presence of crusty patches is a clear visible symptom of lichen growth. Lichens are unique organisms formed from a symbiotic relationship between fungi and algae or cyanobacteria. These crust-like structures can appear on various surfaces such as tree bark, rocks, and soil. The crusty patches often have a distinctive, irregular shape and can exhibit a range of colors, including gray, green, or yellow, depending on the type of lichen and environmental conditions.

In contrast, the other symptoms such as yellow spots, greenish film, and leaf discoloration generally relate to other issues like nutrient deficiency, plant disease, or algal blooms, rather than being indicative of lichen presence. This makes crusty patches a hallmark sign for identifying lichen growth, showcasing their unique morphology in the environment. Understanding these symptoms can be crucial for proper lawn and ornamental pest management, as lichen growth is typically not harmful to healthy plants but may indicate other underlying environmental conditions.