Page 26 - GreenMaster Fall 2023

Nematode populations on a site can be assessed by collecting soil cores and sending them to a lab to have the PPN extracted and counted. This is a good practice on golf course putting greens where the low mowing heights and increased stress can increase the likelihood of symptoms or weakened plants when PPN populations are moderate to high.
Bacterial wilt
Bacterial wilt of annual bluegrass caused by Xanthomonas translucens pv. poae on, especially on putting greens, collars, and approaches. Individual leaves will wilt and turn reddish-brown or yellow and die. Whitish-ten, dime-sized spots may appear, and irregular patterns or streaks may form in severe cases. These symptoms may appear between June–October, and this disease is more severe during extended periods of rainfall. Warm and humid conditions are thought to be important for disease, however the exact environmental conditions conducive to bacterial wilt are not well known.
Bacterial etiolation
Management recommendations for bacterial wilt include mowing only once the turf is dry to decrease the spread of this disease. Mowers should be dedicated for affected greens and should be disinfected with bleach after use. Aggressive cultural practices such as verticutting, topdressing, and aeration are not recommended when the pathogen is active.
Bacterial etiolation
Bacterial etiolation of bentgrasses is caused by Acidovorax avenae subsp. avenae. This disease may also be referred to as bacterial decline of creeping bentgrass. Creeping bentgrass at green-height is susceptible to bacterial etiolation, but light-to-moderate symptoms may occur on annual bluegrass, fescues, and bluegrasses.
The symptoms begin as small (15–30 cm) irregularly-shaped spots of foliar discolouration progressing from green to a light-green or yellow. Often associated with discolouration, the affected leaf blades elongate (this process is called etiolation), extending 0.75–4.0 cm above the turf canopy. Damage is typically most severe on intensively managed putting greens and symptoms first appear on the most stressed or trafficked areas of the turf stand due to frequent and repetitive mowing and rolling practices. Although bacterial etiolation is initially a
cosmetic problem, high summer temperatures (>30°C) can lead to thinning and necrosis of the foliar canopy.
To manage this disease, you must minimize plant stress (i.e raise mowing height, fertilization, reduce traffic). As with bacterial wilt, a dedicated mower is recommended for severely infested areas.
FIND IT ONLINE
If you are looking for Publication 845 on OMAFRA’s website and it says “404 Not Found”, then it is because they are reformatting their website and some hyperlinks have not yet been updated. Additionally, Publication 384 – Turfgrass Management Recom- mendations – has been missing from OMAFRA’s website since December 2022 and OMAFRA does not plan on publishing an updated version. You may reach the Guelph Turfgrass Institute with questions or concerns about integrated pest management at GTI@uoguelph.ca or on social media @GuelphTurf. GM
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26 • CGSA • GreenMaster