Published on Monday, 28 May 2012 01:05
Written by Karl Danneberger
Diseases caused by Drechslera spp. were formerly classified as Helminthosporium leaf, crown, and root diseases. The fungus attacks cool season turfgrasses during the cool wet weather of spring and fall.
. Initial purple lesions appearing on Lolium perenne
. Lesions continue to develop with a purple to brown border with a tan colored center.
Drechslera leaf spot/melting-out symptoms initially appear as leaf spot lesions. The lesions initially appear as small purple colored dots. These lesions turn a gray to tan color with a dark purple to brown border. In the leaf spotting stage these diseases do not normally cause significant injury to the plant. However, as temperatures increase, infection may occur in the crown, stems, and roots where the plants eventually turn a straw colored and die. This is known as the melting-out phase of the disease.
. Melting-out symptoms on Kentucky bluegrass
The symptoms and conditions favorable for Drechslera spp are similar on all the turfgrass species listed below except for one – red leaf spot. Red leaf spot develops during hot dry weather of summer. This disease attacks primarily Agrostis capillaris
(colonial bentgrass) but has been reported on some of the newer Agrostis stolonifera
(creeping bentgrass) cultivars.
• Resistant cultivars, especially Poa pratensis
(Kentucky bluegrass) cultivars are available that are resistant to Drechslera leaf spot/melting-out disease.
• Maintain adequate fertilization levels. Drechslera leaf spot/melting-out disease is associated with turf that is overly fertilized or not fertilized in the spring
• Mow at the higher end of the optimum cutting height for each turfgrass.
• Reduce the amount of thatch present.
Leaf spot/melting-out pathogens associated with cool season turfgrass species.
|Turfgrass Species||Drechslera species|
|Poa pratensis|| Drechslera poae|
|Festuca spp.|| Drechslera dictyoides|
|Lolium perenne || Drechslera siccans|
|Agrostis spp. (primarily A. capillaris)|| Drechslera erythrospila|