You Are Here: Management Updates 1999 Archive June 11, 1999

Date: June 11, 1999
Category: Diseases
Subject: Ascochyta Blight, Fairy Ring, Over-watering, Fusarium Patch

The worry about the high temperatures earlier in the week has subsided, but lack of rain continues to dominate the environmental conditions. The recent cool nights and warm days have relieved some of the stress. It looks like there will be significant rain early next week which may trigger fungal activity. Despite the recent heat stress, diseases have not been too active because it is dry.

Samples this week were associated with heat/water stress or excessive irrigation. Non-irrigated lawns are in drought dormancy. Some samples from irrigated areas show the white bands in leaf blades associated with heat stress. These same samples had ASCOCHYTA BLIGHT, a relatively minor tip blighting fungus that causes an unsightly look but rarely affects the whole plant. The blighting is usually removed by mowing once better growing conditions return. Each tiny black fruiting body in the infected blades contains hundreds of spores that are released by water and spread by mowing, so you can get many blighted tips in a short time. Ascochyta seems to be unusually prevalent and severe this year.

FUSARIUM species are also active where overwatering has been done. Fusarium can rapidly blight turf during hot weather and move into the crowns and roots and kill the plants. It is associated with excessive moisture and high nitrogen fertility.

Several samples arrived this week with problems due to insufficient watering. The samples were compacted, thatchy, and, in a couple of cases, infested with FAIRY RING mycelium that tends to be hydrophobic, contributing to the problem. Spiking, wetting agents and thorough hand-watering of problem areas may help. If the roots look white and healthy, water should probably bring them around. The long term solution involves aeration and dethatching.

Several samples arrived with problems due to overwatering. Overwatering presents several problems. It encourages fungal growth allowing leaf spot fungi such as DRECHSLERA move into the crowns and roots, killing whole plants. It also fills the air pores in the soil and deprives the roots of oxygen. It is important to observe soil moisture before adding more water. Even in hot weather, a good soaking irrigation can last for several days to a week depending on the type of turf.

Last year at this time, I was receiving FUSARIUM PATCH (PINK SNOW MOLD) samples. If next week brings cool, wet conditions, some areas may see the small greasy spots suddenly appear. After the recent heat, it may trick you into thinking it's Pythium blight. If Fusarium patch does appear, please send samples, so we can make isolations for the UMass research and teaching program.

- Submitted by: Dr. Gail Schumann