Monilinia Blight Forecast Post #5 May 1st

Thursday, May 1, 2025

More emerged apothecia were noted at the monitoring sites this afternoon.  

Warm temperatures and rain are forecast for this weekend so development and Monilinia infection may advance quickly.

Many growers were noted spraying this afternoon in anticipation of the coming wet weather. 

Current bud development taken May 1st: 

Early varieties (Duke) - 60% F2 stage

Mid-season Varieties (Draper, Bluegold)- 45% F2 stage

Late Varieties (Burlington, Liberty) - 10% F2 stage

Spray timings for Monilinia Blight should target 40% of buds at F2 stage with active apothecia to give fungicide coverage through periods of free moisture.   

 

Most Growers will choose to apply with one of the Group 3s for their first application.

There are a couple things we should remember in order to fine tune our application.  

-Group 3's move rapidly into the plant after application and most have a rain fastness of one hour.

-Group 3's are very locally systemic and windy conditions during application can effect coverage and decrease effectiveness.  

-Group 3's have decent post infection activity and maybe applied up to 72 hours after an infection period and still provide some activity.  There maybe some risk to relying on post infection activity so growers should plan on applying ahead of wet infection periods.

-Frost can dramatically increase the susceptibility of buds to Monilinia infection.  This increase in susceptibility can last up to 4 days after a frost.  Farm Data Tools weather days shows a frost in many locations on April 29.

-Infection can occur much more quickly at warmer temperatures.   For interest see the table below.

A screen shot of a chart

AI-generated content may be incorrect.

 - Moisture from rain or fog is required for an infection period and dew is thought not to be enough.