Strawberry Disease Control

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

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 initiated no later than 10% bloom and/or prior to disease development.

For control apply the following combinations:
Application #1

captan (M3) at 4.0 lb 50WP/A plus Pristine (pyraclostrobin + boscalid, 11 + 7) at 18.5 to 23.0 oz 38WG/A
Application #2
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
Application #3
Captevate (captan + fenhexamid, M3 + 17) at 3.5 to 5.25 lb 68WDG/A

For subsequent applications, alternate:
Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A plus captan (M3) at 4.0 lb 50WP/A
or
Cabrio (pyraclostrobin, 11) at 12.0 to 14.0 oz 20EG/A plus captan (M3) at 4.0 lb 50WP/A
or
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 two 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 can cause serious losses in strawberry plantings in high tunnels and the field if not controlled properly. Development is favored by moderate temperatures (59-77°F) with prolonged periods of high relative humidity and surface wetness. Control of gray mold begins with preventative fungicide applications. Apply at 5-10% 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.

Application #1
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
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 23.0 oz 38WG/A
Application #3
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 any of the following:
● 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

Strawberry Leather Rot
For additional information on leather rot see the article titled Controlling Leather Rot of Strawberry in the April 10, 2009 issue of WCU.

In New Plantings:
Aliette (fosetyl-Al, 33) at 2.5 to 5.0 lb 80WDG/A. Begin 14 to 21 days after planting and continue on a 30 to 60 day interval as long as favorable disease conditions occur.
or
Ridomil Gold (mefenoxam, 4) at 1.0 pt 4E/A. Make one application at transplanting plus an additional application at fruit set or 30 days before harvest.

In Established Plantings:
Aliette (fosetyl-Al, 33) at 2.5 to 5.0 lb 80WDG/A
or
Ridomil Gold (mefenoxam, 4) at 1.0 pt 4E/A
Apply in spring before first bloom and repeat once in the fall.

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