Friday, September 26, 2014

Manage Spring Dead Spot with Fungicide Application Now

Did your Bermudagrass lawn suffer from spring dead spot disease this year? The UGA Extension publication "Identification and Control of Spring Dead Spot", by Extension specialists Alfredo Martinez, J.B. Workman, and F. C. Waltz, explains that the disease is especially prevalent after a hard winter, such as the one we experienced last year. This means that any Bermudagrass lawn affected this past growing season had plenty of company.

Even though it may seem counter-intuitive, chemical controls for spring dead spot (SDS) should be applied in fall, when soil temperatures are still above 60 degrees F, according to Martinez et al. This application can help prevent re-emergence of the disease next year.

SDS first shows up in late spring. The publication says this about signs of infection: "As turfgrass 'greens up,' well-defined circular patches of dead, bleached-out grass are noticeable in affected areas. Non-infected bermudagrass resumes growth, accentuating the infected areas."

The authors add, "Patches can get larger year after year." To avoid this outcome, altering cultural practices to promote good health of the lawn is important. One practice in particular is to avoid  applying more than a half-pound of nitrogen fertilizer per thousand square feet after mid-September; another is to consider applying a potassium fertilizer, at the rate of one pound potassium per thousand square feet, in fall.

The Turf section of the Georgia Pest Management Handbook, homeowner edition, by Extension homeowner IPM specialist Elizabeth Little, agrees with these recommendations, and includes a listing of currently recommended products for controlling SDS. Regardless of the product selected from the list, be sure to follow label recommendations and safety precautions.

The Turf section of the handbook linked above, which also contains information about insect and weed control in lawns, lists specific cultural practices that can help to manage SDS:
  • "Avoid late summer or fall applications of nitrogen fertilizers which may enhance disease severity.
  • Use ammonium sources of nitrogen fertilizer from spring through early August.
  • Control weeds in affected turf to enhance recovery from spring dead spot.
  • Apply moderate to high levels of phosphorus, potash, and minor elements.
  • Improve drainage of turf.
  • Reduce thatch.
  • Use preventive fungicide applications in late September and October."