Strawberry Diseases and Freezes – April 26

Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu

Wind Damage
Strawberry leaves and stems, especially succulent new growth, can become bruised and develop blackened areas after windy weather. Please see this past WCU article Bruising on Strawberry Leaves, by Jerry Brust for pictures of wind damage. This type of damage is not a disease and has not been associated with increased risk of disease, so control measures are not needed when you observe wind damage symptoms.

Freeze Damage
Except for this past week, the season has been relatively free of frost risk to strawberries. There were below freezing temperatures in some areas on April 22, 23 and 26. Based on data from DEOS Almanac, freeze damage to unprotected strawberry flowers may have occurred in some locations, especially in northern and western Delaware. Below are minimum temperature maps for April 22 and 23. A map of the April 26 minimum temperatures was not available at the time I wrote this article, but it was 30°F at my house near Ellendale this morning. The weather forecast suggests that risk of freezes is past for the foreseeable future.

Daily minimum temperatures in Delaware on April 22 and 23, 2024

Daily minimum temperatures in Delaware on April 22 and 23, 2024

Disease Risk Forecast

NEWA Strawberry Diseases Risk Levels for seven Delaware locations are compiled in the table below. Good news for strawberry growers this year: disease risk has been and continues to be low across the state.

Strawberry Anthracnose and Botrytis Infection Risk from NEWA on April 26, 2024

NEWA strawberry disease risk for Delaware is low.

When risk levels are low (green highlight) fungicides are not needed to control disease. When risk levels are moderate (orange highlight), fungicides should be applied if other factors are present that increase disease risk, such as susceptible varieties or a history of disease in the planting, AND fungicides have not been applied for 7-14 days. When risk levels are high (red highlight) apply a highly effective fungicide as soon as possible if no fungicides have been applied for 7-14 days.

You can get the most recent and relevant strawberry disease risk information by checking the NEWA model for the DEOS station closest to your field.