Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Botrytis (gray mold) and blossom blight can cause serious losses in strawberry plantings if not controlled properly. Development is favored by moderate temperatures (59 to 77°F) with prolonged periods of high relative humidity and surface wetness. Control of gray mold begins with preventative fungicide applications. Apply at 5 to 10 percent bloom and every 10 days until harvest. During periods of excessive moisture, spray intervals of 5 to 7 days may be necessary. Rotate fungicide chemistries to aid fungicide resistance management. See the 2008 Commercial Vegetable Crops Production Recommendations for more info and other strawberry pest control options.
Application #1: captan (M3) at 4 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1 lb 70WP/A
or Switch (cyprodinil, 9) at 11-14 oz 62.5WG/A
Application #2: Elevate (fenhexamid, 17 – see restrictions) at 1.1 to 1.5 lb 50WDG/A
or Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23 oz 38WG/A
Application #3: captan (M3) at 4 lb 50WP/A plus Topsin M (thiophanate-methyl, 1) at 1 lb 70WP/A
or Switch (cyprodinil, 9) at 11 to 14 oz 62.5WG/A
For subsequent applications, alternate:
Captan (M3) at 4 lb 50WP/A, or Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A, or Switch (cyprodinil, 9) at 11 to 14 oz 62.5WG/A
or Pristine (pyraclostrobin + boscalid, 11 +7) at 18.5 to 23 oz 38WG/A
or Thiram (M3) at 4 to 5 lb 65WSP/A