As we move beyond the peak demands of summer, it’s time to shift our focus to the challenges that lie ahead – particularly the active tropical season, which brings extended leaf wetness, saturated soils and reduced sunlight. These conditions create a perfect storm for increased disease pressure on putting greens. Staying ahead of these challenges through late summer and early fall in the Southeast requires a combination of strategic fungicide applications and consistent cultural management practices.
Soilborne diseases such as take-all root rot, Pythium root rot and spring dead spot become especially aggressive during this period and demand timely preventative action. Effective fungicide programs rely heavily on soil temperature thresholds, and treatments must begin sooner rather than later. Once soil temperatures dip below 86 degrees F, critical treatment windows begin to open and waiting too long can compromise control.
Perhaps the most deceptive aspect of these pathogens is their tendency to infect turf in late summer and fall, yet visible symptoms may not appear until late winter or early spring. By the time damage becomes apparent, the opportunity for effective intervention has passed. That’s why proactive management starting in September is key to preventing long-term turf decline and ensuring strong root health going into the busy fall season.
For take-all root rot, fungicide applications from DMI (demethylation inhibitor) or Qol (strobilurin) groups provide the most effective control and should be applied when soil temperatures fall into the 86 F to 75 F range. Those two fungicide groups and the phosphonates also work on Pythium root rot, although it is a disease that can be active a much wider range of soil temperatures. SDHI (succinate dehydrogenase inhibitor) fungicides are best suited for managing spring dead spot and should be applied in rotation with other products when soil temperatures are between 70 F and 55 F. During the transitional and often unpredictable weather of late summer and early fall, broad-spectrum fungicides offer valuable protection by targeting multiple pathogens and often providing extended residual activity. It is essential to rotate modes of action based on FRAC codes to reduce the risk of fungicide resistance and to strictly follow label-recommended intervals between applications, typically ranging from 14 to 28 days. Proper rotation not only improves disease suppression but also preserves the long-term effectiveness of your fungicide program, ensuring reliable control year after year.
While fungicides serve as the first line of defense against soilborne pathogens, their effectiveness increases significantly when integrated with sound cultural practices. Techniques such as needle-tine aeration, enhancing surface drainage, slightly raising mowing heights, occasionally rolling greens instead of mowing, and strategic hand watering help reduce plant stress and create conditions less favorable for disease development. Together, these cultural practices support turf health and optimize the performance of fungicide applications.
As we enter this transitional season, now is the time to be proactive – not reactive. Monitoring soil temperatures, planning fungicide rotations and doubling down on cultural best practices will position your greens to withstand the dual pressures of disease and weather stress. The decisions made in September will echo well into spring – determining not just how your turf survives the busy fall and winter seasons, but how quickly and cleanly it recovers in spring.
Southeast Region Agronomists:
Jordan Booth, Ph.D., senior director, USGA Course Consulting Service – jbooth@usga.org
Chris Hartwiger, director, Agronomy – chartwiger@usga.org
Chris Neff, agronomist – cneff@usga.org
Mitch Leininger, agronomist - mleininger@usga.org