Diplodia Leaf Streak: A Dual Threat to Corn Crops

Developed by Nolan Anderson of Texas A&M University and Kiersten Wise of the University of Kentucky, this collaborative effort aims to unravel the complexities of Diplodia leaf streak, a corn disease caused by the fungus Stenocarpella macrospora, which not only affects leaves but can also trigger Diplodia ear rot.

The initial symptoms of Diplodia leaf streak typically manifest in the mid-lower canopy, appearing as small, round, dark brown or brown lesions on leaves. These lesions may exhibit concentric rings, a distinctive feature that sets them apart. As the disease progresses, the lesions expand, forming long streaks measuring several inches to over 12 inches. Additionally, elongated elliptical-shaped lesions may emerge, bearing an uncanny resemblance to lesions caused by northern corn leaf blight.

Within mature lesions, researchers have identified small, dark, round fungal structures known as pycnidia, providing valuable clues for diagnosis and study. The fungus's ability to overwinter on residue and its reported capacity to infect seeds further complicates the management of Diplodia leaf streak. Infection is not limited to a specific growth stage, making it a constant threat throughout the corn plant's development.

Spores of Stenocarpella macrospora are dispersed by both wind and splashing water, underscoring the challenges farmers face in preventing the disease's spread. Disease development is particularly favored by high humidity and moderate temperatures ranging from 64 to 81°F, emphasizing the climatic conditions that intensify the impact of Diplodia leaf streak.

Adding to the complexity is the potential link between Diplodia leaf streak and Diplodia ear rot. While each disease can occur independently, the intricate relationship between the two remains poorly understood. Researchers are diligently working to decipher the factors influencing their coexistence and potential interactions.

Surprisingly, Diplodia leaf streak has not been reported to cause direct yield loss, offering a small reprieve for corn farmers. Although immediate management is not deemed necessary, a proactive approach involving crop rotation away from corn and residue reduction can limit the fungus's overwintering potential. The hybrid susceptibility of corn to Diplodia leaf streak remains an ongoing research focus, with the hope of developing targeted strategies to mitigate its impact.

In a notable challenge for farmers, there are currently no foliar fungicides specifically labeled for Diplodia leaf streak. This underscores the urgency of continued research efforts to fill the knowledge gaps and provide practical solutions for managing this dual threat to corn crops. To learn more about Diplodia Leaf Streak of Corn visit the CPN encyclopedia.