Tuesday, November 6, 2007 - 3:15 PM
168-9

Screening for Azoxystrobin-Resistant Colletotrichum cereale Isolates of the Mid-South.

Joseph Young, Maria Tomaso-Peterson, and Gregg Munshaw. Mississippi State University, 206 Dorman Hall Box 9655, Mississippi State, MS 39762

Anthracnose, caused by Colletotrichum cereale, is a destructive disease on creeping bentgrass putting greens in the mid-South. Azoxystrobin has been used to prevent or control anthracnose for ten years and has a high potential for inducing fungicide resistance among C. cereale isolates. Azoxystrobin-resistant C. cereale isolates have been identified throughout the United States, but reports from the mid-South are lacking. The objective of this research was to screen isolates of C. cereale collected from symptomatic creeping bentgrass putting greens in the mid-South for azoxystrobin resistance. Thirty monosporic isolates of C. cereale were transferred to ¼-PDA amended with 0.031 or 8 ppm azoxystrobin plus salicylhydroxamic acid and incubated at room temperature for 6 days in the dark. Relative growth (RG) of C. cereale was determined by dividing the mycelial growth on the azoxystrobin-amended media by the mycelial growth on the non-amended control. Colletotrichum cereale isolates displayed little or no sensitivity to azoxystrobin. The 8 ppm treatment had the least amount of mycelial growth; however, the range of RG was 57 to 91% with an average RG of 75%. The RG at 8 ppm for these isolates was similar to RG of azoxystrobin-resistant isolates identified in similar studies. Additional studies will be conducted on C. cereale isolates to confirm azoxystrobin resistance.