Gray leaf spot

Gray-brown leaf lesions with dark borders; leaves twist and wither, giving a scorched, drought-like look. Fuzzy gray sporulation under humidity.

The fungus invades the leaf blades and causes symptoms such as wilting, total blighting, fish-hook leaf tip, brown or gray discoloration at the tip of the leaf, and brown spots or leaf lesions with yellow halos. These symptoms can result in a reduction of turfgrass quality and can even lead to death of the affected plants or large swards of grass.

The signs of the pathogen causing gray leaf spot include the presence of uniquely shaped conidia, which are reproductive spores, and thick masses of grayish conidia and conidiophores on the infected leaves. These conidia and conidiophores give the leaves a felt-like or fuzzy appearance. Additionally, under high magnification, the presence of conidia and conidiophores can be confirmed.

The fungus can overwinter in infected plant debris, and produce spores that can infect new growth in the spring. The spores are spread by water and wind, and the fungus can also infect the plant through natural openings, such as leaf sheaths, and wounds.

Gray leaf spot is a sporadic disease that favors wet and dry cycles. An increase in relative humidity can increase disease severity. The fungus can infect the plant under a wide range of environmental conditions, but it is most active when temperatures reach or exceed 68°F, with the optimum temperature range for growth being 77-86°F. Symptoms begin in June or July and may continue until September/early October. Young seedlings are particularly susceptible to the disease.