Golf Course Management

DEC 2018

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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60 GOLF COURSE MANAGEMENT 12.18 toms among cultivars (described below in the section "Resistant bermudagrass cultivars"). Bermudagrass mites begin to damage growing bermudagrass terminals as soon as the turf greens up. e most characteristic damage caused by the bermudagrass mite is the "witches' brooms," the stunting of ter minals (Figure 2). Witches' brooms appear within 13 days of feeding (5) and are caused by permanent shortening of internodes. e mechanism by which mite infestation causes the shortening internodes is uncertain. Does the mite inject a toxin or growth regulator during feeding, or transmit a virus to the host? No study has conclusively demonstrated the mechanism. We also cannot develop a treatment threshold without knowing how many mites per stem are required to cause the witches' brooms. Terminals stunted by witches' brooms fail to grow and recover from the damage. ese stunted terminals often die in the winter, and the damaged stems and stolons do not produce new shoots. Eventually, the infested turf becomes thin, and bare spots begin to ap pear (Figure 3). As infestation continues, the bare or thinned patches expand and coalesce. e most severe damage often appears on the slopes and at the edges of bunkers (Figure 4), suggesting that the severity of damage may be closely related to moisture stress. Without reducing or removing the infestation in the surrounding turf, resodding the dead patches with bermudagrass (regardless of the cultivar) often results in the decline of the replacement sods over time (Figure 5). Damage by the bermudagrass mite may exacerbate other pest problems. Weeds often invade thinned and bare patches (Figure 3), and mite weakened turf is more susceptible to attacks by bermudagrass scale, nematodes and Helminthosporium diseases (that is, leaf spots caused by Drechslera and Bipolaris). Searching for management solutions for bermudagrass mite Monitoring Scouting for bermudagrass mite infesta tions is achieved by surveying for the classic symptom of witches' brooms, which is dif ferent from the damage caused by other mite Figure 2. A comparison of Celebration bermudagrass terminals damaged by the bermudagrass mite (top and middle) and a healthy terminal (bottom). Photos by JC Chong Figure 3. Bermudagrass turf severely damaged by the bermudagrass mite is thinned and patchy, allowing weeds to invade.

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