Which of the following diseases is characterized by a more advanced decay of plant tissue and typically occurs later in the season?

Phytophthora is a group of water mold pathogens that are particularly notorious for causing significant issues in various crops, especially as the season progresses. The diseases caused by Phytophthora often lead to advanced tissue decay, which is evident in the symptoms seen on infected plants. This organism thrives in warm, wet conditions, making late-season infections more prevalent as environmental conditions may support its growth and development.

Unlike Pythium, which also thrives in wet conditions and is more commonly associated with seedling damping-off early in the season, Phytophthora tends to affect mature plant tissues later in the growth cycle. Fusarium, on the other hand, is known for causing wilt diseases and can affect plants throughout the season but does not typically present with the same advanced decay before full maturity. Rhizoctonia may also cause decay but is often associated with root rot problems rather than the advanced tissue decay seen with Phytophthora.

Thus, Phytophthora's role in causing late-season decay aligns with the question's description, helping to identify it as the correct answer.