Managing Anthracnose On Golf Course Putting Greens (P2)
Colletotrichum cereale overwinters in the thatch of putting greens and lives on organic matter. As environmental conditions become favorable for its growth with increasing temperatures and high humidity in the plant canopy, fungal mycelium will begin growing in search of susceptible host material. As the mycelium extends to older, senescing leaf material, the terminal end of the mycelium will enlarge and darken to form an appressorium (ia) (Figure 4). The appressoria produce a penetration peg that penetrates the epidermal cells of the leaf, allowing the fungus to consume simple carbohydrates from the plant. As the fungus colonizes the plant, an asexual fruiting body called an acervulus (i) is formed within the epidermal cells of the leaf. The acervulus gives rise to black, sterile hairs called setae that extend out of the leaf and are a key diagnostic characteristic of C. cereale infection (Figures 5 and 6). The acervulus also produces copious amounts of asexual spores known as conidia that continue the infection process (Figure 6). Conidia are dispersed by water movement and machinery passing through the infected area. As long as environmental conditions remain favorable for fungal growth, these conidia will germinate and infect susceptible plants as previously described.
There is little research published on the management of anthracnose, mostly due to the difficulty of getting consistent infection over a study area. Researchers at Rutgers University have determined a method of inoculation on annual bluegrass putting greens that has allowed them to conduct many studies to determine management practices that either exacerbate or minimize anthracnose severity. Unfortunately, minimal information is available for management practices on creeping bentgrass; however, these practices should be consistent with managing anthracnose on either annual bluegrass or creeping bentgrass.
Cultural Management Practices. The key goal in any anthracnose management strategy should be to reduce turf stress and have the healthiest, most vigorous stand of turf possible. There are many agronomic practices incorporated into management strategies that actually increase stress on putting green turf such as reduced nitrogen fertility, extremely low mowing heights, decreased irrigation and cultural practices. Even though these practices increase turf stress, they are continually performed to increase ball roll and surface playability. The following paragraphs will briefly discuss alterations to the extreme management practices that have decreased anthracnose severity in studies conducted on annual bluegrass putting greens.