2023 Updates and Seasonal Outlook for NS_ May 31_ frost& weather updates, botrytis management and pollination

Wednesday, May 31, 2023


This post will focus on frost and weather updates, botrytis management and pollination.


Frost and Weather Updates


May 30 Frost Damage Update:

Regarding Tuesday’s (May 30) morning’s frost, I made a summary of minimal temperatures from wild blueberry weather stations: http://www.novascotiawildblueberryblog.com/2023/05/post-frost-event-summary-may-30-2023.html.


I checked fields in Pictou (Blue Mt., Moose River and Blanchard Road) where stations reported below -2 c for about 6-7 hours. Luckily, all fields in those areas were still in the pre-bloom stage with limited open blooms. I don’t think growers should concern about this frost.


The next potential frost is going to be around the full moon (June 4) and here are some words from weather experts:


“The weather pattern is most likely going to be a cool and wet one this weekend – all models are predicting it actually.  This means cool but overcast and light to moderate NE winds.  Temps would likely be in the 5 to 10C range for several days if this pattern ‘stalls’ which is the current indication.  So that’s a saving grace as long as the skies don’t clear out during the spell of weather.  Even if they did clear out for a short period over the weekend, it could be brief and the ground should already have moistened up with showers/drizzle.”- from ECCC.


Most mainland fields will be in full bloom or in a high percentage of bloom stage (20% and above) which puts those fields at a greater risk of frost damage. If you are thinking to apply fungicides (Pristine and Merivon), the most effective window would be 12-24 hours before. Based on this, the time frame (regardless of the rain we might get this weekend) is Friday to Saturday morning.


Weather Update:


Perennia’s Tree Fruit Specialist, Michelle Cortens, wrote a summary about this year’s weather, including GDD and precipitation. https://www.nstreefruitblog.com/2023/05/orchard-outlook-newsletter-vol-23-no-7.html#h1. This is a very nice information for you as well. Thanks, Michelle!


Content from Perennia’s Tree Fruit Blog:



2023 Degree Day Accumulations


Cumulative degree days continue to be slightly behind the 5- and 10-year averages for plant and insect development (Figure 1). The lack of heat equates to plant growth being about 2 to 3 days behind average. The average temperature for May is 10.2°C compared to the 10-year average of 11.2°C. 


Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to May 29 for the past 17 seasons. Provided by Jeff Franklin (AAFC).

·                Approximately 8% less plant development heat units compared to the 5-year average, and 9% less compared to the 10-year average.

·                Approximately 22% less plant development heat units compared to 2022, and 21% less compared with 2021.

·                Approximately 10% less insect development heat units compared to the 5-year average, and 15% less compared to the 10-year average.



2023 Precipitation


The Kentville weather station has recorded less than half the monthly average rainfall at 31 mm out of 74 mm. Jeff Franklin assembled the total precipitation for the months of April and May, for Kentville, over the last 111 years and sorted from lowest to highest. The 10 driest years are shown in Table 1 and 2023 ranks as the 5th driest year.

Table 1: Total precipitation for the months of April and May in Kentville over the last 111 years, showing the 10 driest years. Provided by Jeff Franklin (AAFC).



Botrytis Management

If you are in areas where typically more prone to botrytis infection, such as coastal areas, and wet/fog areas and if your fields are weedy (sheep sorrel is an important host) with very dense patches, you should consider and monitor the situation for treatment application. The fungus begins to sporulate at early bloom, so the best time to apply (if needed!) the first application is when about 30-40% of the flowers are open. Closed flowers are resistant to infection. A second spray can be applied about 7-10 days later.




Overwinter beehive health: last I checked with some beekeepers, the winter losses for NS bee hives were around 15-20% which is still under an acceptable range. Bees survived over the winter look very good and they gain weight very fast. Up to this point, a couple of beekeepers are still feeling there is enough nectar flow with the rain we will get next week, it should be a very positive sign for pollination.