2023 Updates and Seasonal Outlook for NS_ 2nd Blight Line Post_ April 25

Tuesday, April 25, 2023

Growing Degree Days (GDD) Summary

Here is a summary of the most up-to-date GDD from 13 weather stations in wild blueberry fields.


Figure 1. GDD Summary, April 25, 2023

For fields/areas with GDD above 150 GDD, pre-emergence herbicides (chikara, ignite, velpar, spartan etc.) can be applied now, but please watch the 213 GDD threshold as after 213 GDD, plants are actively growing and damage could occur to newly emerged tissues.


For crop fields and monilinia, some very early fields (fields in the Southshore counties and fields around Newville Lake and Halfway River in Cumberland County) are at or above 40% F2, but based on the weather forecast for those areas, an application can be made until next rain and wet period. Most average fields in Colchester and Cumberland are around 20% F2. Fields in Pictou, Antigonish and Cape Breton are still looking in between 5%-10% F2.


After fields reach 40% F2 and above, a Monilinia blight application should be made before a forecasted wet/rainy period. But, if it is forecasted to be a dry period, then an application can wait until before a wet period. If we are getting average temperatures of 10 or 14 degrees Celcius, a 6- 8 hours wetness duration could bring a high risk of infection (Figure 2).



Figure 2. Severity Rating of Monilina Infectinn Periods