|
As warmer, more humid summer weather comes to the northern half of Illinois, we will see more incidence of a disease of golf turf called anthracnose.
This disease most commonly affects Poa annua (and Poa trivialis) on greens and fairways (see photos 1 & 2), and causes a severe stem and crown rot called “anthracnose basal stem rot” (see photo 3).
When the disease is attacking Poa, nearby creeping bentgrass usually remains healthy.
Unfortunately, anthracnose fungi (Colletotrichum graminicola) can also attack creeping bentgrass (especially Penncross) and cause a symptom that looks similar to a localized dry spot (see photo 4).
Colletotrichum often infects bentgrass stolons, roots, and crowns (photo 5), which causes a slow decline and thinning of the turf.
Interestingly, when bentgrass is attacked, nearby Poa annua or P. trivialis is usually unaffected.
Apparently there are different races or biotypes of this fungus that attacks only one genus at a time!
If you start to see small, scattered spots of Poa turning off color (yellow to orange to reddish colors are possible) in distinct patches, look for signs of the anthracnose pathogen and fruiting bodies at the stem base or along the stem, or on leaf sheaths just above the crown.
Like dollar spot, anthracnose is favored by low N fertility, and the activity of fungicides can be improved by tank mixing some soluble N with a fungicide.
Anthracnose can be distinguished by scattered areas of (primarily) Poa annua turf that develop bright yellow flecks or spots the size of a dime, and by the distinctive black fungal decay at the base of infected plants.
Many superintendents who have had problems in the past with anthracnose on Poa greens are reporting excellent results with Heritage fungicide.
If you have commonly included a benzimidazole derivative fungicide (eg Cleary's 3336) in programs for anthracnose control, you should consider switching to a DMI or Heritage/Compass fungicides to avoid developing a resistance problem.
|
|
|
Photo 1.
Photo 2.
Photo 3.
Photo 4.
Photo 5.
(click on an image to enlarge it.)
|
|
