Penn State Extension: Watch for fire blight, apple scab
Warmer temperatures are forecast for April 15-16, which will likely bring on fruit tree blooms, according to Penn State Extension, with rains expected as well. This will trigger a “significant infection event” for apple scab, according to the Extension service.
Pink Lady king blossom about to pop open. Apple trees in bloom will need protection to prevent fire blight April 15-16. Photo: K. Peter, Penn State
Rain is in the forecast for Saturday and Sunday. Combined with warm temperatures, this will trigger a significant infection event for apple scab and fire blight. Trees will need to be protected prior to the weekend to prevent disease.
With warm weather comes the threat of fire blight when trees are in bloom, especially if a moisture event (rain, fog) is in the forecast. The weekend of April 15-16 will “prove to be a doozy if the forecast comes to fruition.” Based on the upcoming forecast, those days are predicted to be a major apple scab and fire blight infection period.
In addition, there is a potential for rain on April 17-18, causing the apple scab infection period to be extended. Because the number of available overwintering apple scab spores are close to peaking and the conditions will be favorable for infection, disease pressure will be high. For fire blight, the Infection Potential EIP value will be around 200 in Adams County, indicating a potential for many infections to occur if there is a wetting event.
Growers need to monitor their orchards very closely late week to ensure protection is on the trees prior to the weekend to prevent fire blight and apple scab. In addition, brown rot blossom blight for stone fruit is a concern.