2023 Updates and Seasonal Outlook for NS_ May 29 Frost Advisory for Eastern and Northern Mainland Nova Scotia and Cape Breton

Monday, May 29, 2023

Frost Advisory for Eastern and Northern Mainland Nova Scotia and Cape Breton

(Expected on early Tuesday morning, May 30)



Hi, everyone


There is a frost advisory issued for Eastern and Northern Mainland Nova Scotia (Figure 1). The forecasted minimum temperatures are from -2 c to + 4 c.

More information about frost damage in wild blueberry production? Please check last week’s blog post: http://www.novascotiawildblueberryblog.com/2023/05/2023-updates-and-seasonal-outlook-for_25.html.

On Tuesday morning (May 30), I will give an update on overnight and early morning minimum temperatures and durations from wild blueberry weather stations.

Given the crop stages in the frost-affected area, this frost could be concerning for crop fields with a good percentage of open bloom (15-30% and above) in those areas.

Fields in Pictou, Antigonish and Cape Breton are still in the pre-bloom stage with a low percentage of bloom (5%) which put those fields at a lower risk of this frost event, but cold temperatures below -2.2 c could still cause damage to any open flowers.


Pre-Bloom- relatively safe from frost and low temperatures. Those pre-blooms are safe at -5 c and above.



Open-bloom, prone to frost and low temperatures damage. -2.2 C is a critical point for those open blooms.


Fields in Cumberland and Colchester are at a greater risk of this frost event due to the % of bloom in those areas being higher (15-20% and above). If you are using one of the stations close to your fields, please watch and check your GDDs. A station with around and above 400 GDD put fields nearby at greater risk. From this year’s GDD and bloom % (in progress) and field observation, fields near a station with above 400 GDD show that the % of bloom is around 15-20%. Please see Figure 2- GDD summary.



Figure 1. Frost Advisories for parts of Nova Scotia





Growing Degree Days (GDD) Summary and Plant Development Updates

Figure 2. GDD Summary, May 28, 2023

What Can You Do?

1.      There is nothing you can do to change mother nature’s mind but we still have a few recommendations for you to consider.

2.      Check your local temperatures from close wild blueberry weather stations or any source you like. Knowing the lowest temperatures and the duration of the event is beneficial as this can help you to pre-determined the level of damage from frost. https://www.capebretonweather.ca/

3.      You would be able to see symptoms on open blooms and their petals from frost damage a few hours after. Normally, you would be able to see initial signs on petals on the same day but in terms of potential yield reduction, you have to wait until green fruits are set.

Figure 3. Frost damage on wild blueberry flowers


4.      Considering other frost-protection methods.

a.       I don’t think there is much you can do. Some methods we know are burning, copper and zinc, and applying irrigation water, but they are not practical in our region and this crop.

b.      Some fungicides we use during this time of the year offer frost protection features besides their regular disease control function. Pristine (pyraclostrobin and boscalid) and Merivon (Pyraclostrobin and fluxapyroxad) may help with frost protection. It is recommended that those products are put on 12-24 hours before a forecasted frost event.

*When I checked weather stations, the cold temperatures normally start around 3 AM. I hope this is helpful to time your spraying.

** I don’t expect you to apply those fungicides today because of the short notice and high wind, but this would come in handy when any future frost events are forecasted.



I hope we don’t get a bad frost!