What factor primarily contributes to the development of lawn diseases, including brown patch?

High nitrogen levels are a significant factor that contributes to the development of lawn diseases such as brown patch. When nitrogen is applied in excess, it can lead to lush, rapid growth of grass that is more susceptible to disease. Brown patch, caused by the fungus Rhizoctonia solani, thrives in conditions where nitrogen levels are elevated, especially in warm, humid environments that can occur during the summer months.

The over-fertilization with nitrogen creates optimal conditions for fungal growth by promoting dense, succulent grass tissue that the fungus can infect more easily. Additionally, high nitrogen levels can also contribute to other stress factors, such as increased thatch buildup, which can further exacerbate the likelihood of disease development.

In contrast, soil type, excessive sunlight, and low watering frequency may play a role in overall lawn health but are not the primary factors in the development of specific lawn diseases like brown patch. Soil type influences drainage and nutrient availability; excessive sunlight can stress grass types more sensitive to heat; and low watering frequency can lead to drought stress. However, these factors do not have the direct impact on disease conditions that high nitrogen levels do.