Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
It won’t be long before strawberry growers will need to deal with several important diseases. Here are the latest recommendations from the 2010 Commercial Vegetable Production Recommendations.
Anthracnose Fruit Rot
Strawberry anthracnose can be extremely destructive during warm, wet weather, causing significant fruit rot. Symptoms of anthracnose include blackish-brown circular spots on maturing green fruit and soft, sunken (flat) circular lesions on ripe fruit. On ripe fruit, lesions can expand rapidly and are often covered with a pinkish-orange spore mass. Spores are spread from infected to healthy fruit with splashing water. Control of anthracnose always begins with a 7 to 10-day preventative spray program no later than 10% bloom and/or prior to disease development. For control apply the following combinations:
First Application
Captan (M3) at 4.0 lb 50WP/A plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A
Second Application
Captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl. oz 2.08SC/A or Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A
Third Application
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A
For subsequent applications, alternate:
● Captan (M3) at 4.0 lb 50WP/A plus Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A
● Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/ A plus captan (M3) at 4.0 lb 50WP/A
● Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A
To help manage fungicide resistance development, do not make more than 2 consecutive applications of either: Pristine (pyraclostrobin + boscalid, 11 + 7), Cabrio (pyraclostrobin, 11) or Abound/Quadris (azoxystrobin, 11) before switching to another fungicide chemistry.
Botrytis (Gray Mold) and Blossom Blight
Botrytis gray mold and blossom blight can cause serious losses in strawberry plantings in high tunnels and the field 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.
First Application
Captan (M3) at 4.0 lb 50WP/A plus
Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP/A
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A
Second Application
Elevate (fenhexamid, 17 – See restrictions) at 1.1 to 1.5 lb 50WDG/A
or
Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz. 38WG/A
Third Application
Captan (M3) at 4.0 lb 50WP/A plus
Topsin M (thiophanate-methyl, 1) at 1.0 lb 70WP
or
Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A
For subsequent applications, alternate:
● Captan (M3) at 4.0 lb 50WP/A
● Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A
● Switch (cyprodinil, 9) at 11.0 to 14.0 oz. 62.5WG/A
● Pristine (pyraclostrobin + boscalid, 11 +7) at 18.5 to 23.0 oz 38 WG/A
● Thiram (M3) at 4.0 to 5.0 lb 65WSB/A