2023 Updates and Seasonal Outlook for NS_ 1st Blight Line Post_ April 18
This is the first post for the 2023 season on updates,
the outlook for the season, the monilinia blight line, pest alerts etc. We try
to publish 2 posts per week (typically on Tuesdays and Fridays) during the monilinia
season and after that, we will publish posts as information comes in.
Growing Degree
Days (GDD) Summary and 2023 Spring Plant Development Prediction
This year, we are only planning to report GDDs from 13
stations (see Figure 1) because we have research trials and extension needs
from those stations. However, there are different ways to obtain GDDs by
choosing the station you like. To learn how to obtain GDDs, please read this
blog post: http://www.novascotiawildblueberryblog.com/2023/04/2023-wild-blueberry-pest-guide-new.html.
Here is a summary of the most up-to-date GDD from 13 weather stations in wild blueberry fields.
Figure
1. GDD Summary, April 19, 2023
Based on this
information, most of the mainland fields in Nova Scotia could start
pre-emergence herbicide application when the station hits 150 GDD but before
213 GDD. That said, a lot of areas could start pre-emergence herbicide
application anytime soon.
In Figure 3, so far, we
are relatively close to average. For comparison, this year’s degree
accumulations are on track with the year 2019. It is not a bad idea to look at
your records on 2019 management activities.
Figure 2. Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1 to April 17 for the past 17 seasons in Kentville. Provided by Jeff Franklin (AAFC).
Based on every piece of information
I have and confirmed by field observation, we are around 1 week earlier than
average and slightly later than the 2022 season (about half a week later than
last year)
Winter Weather Review
The Environment Canada
weather station in Kentville is used for comparison because historical data is
available. A big thank you to Jeff Franklin (AAFC) for providing those data.
Figure
3: Average monthly temperatures from December through March for the past three
winters, and for 5- and 10-year averages at Kentville AAFC.
Figure
4: Soil temperatures at 5 cm depth at the Kentville Research Station
Overall, we had both
above-average air and soil temperatures most of the time throughout this
winter.
Other observations- weeds and winter damage
Low winter
kill (damage) on wild blueberry fields across the province.
You might
think that you don’t need to control sheep sorrel in your sprout fields because
you think it is “clean”. Please look below the top layers or any areas with
thick protection layers. You would be surprised how many of them are under
protection layers and growers over winter months since we had higher-than-average
air and soil temperatures.
Wild Blueberry Floral
Bud F2 Stage
Please see the below summary table of the percentage of
wild blueberry floral bud at the F2 stage. You can also click on this map to
check those numbers. Detailed information is also available under the Wild
Blueberry Blog- GDD&
Phenology Tracker.
Table 1. Percentage of Wild Blueberry Floral Bud F2
stage
light green (0-20% F2), dark green (20-30% F2), yellow
(30-40% F2) and red (40-100% F2)
|
Wild blueberry production regions, NS |
The average percentage of floral buds at
F2 |
|
|
|
|
Cape Breton |
|
|
|
|
|
Cumberland County |
|
|
Halfway River |
5%-
April 18 |
|
Kirkhill |
0%-
April 18 |
|
Westchester Station |
0%-
April 18 |
|
|
|
|
South West Nova Scotia |
|
|
Queens County |
5%-
April 19 |
|
|
|
|
Hants County |
|
|
|
|
|
Halifax County |
|
|
|
|
|
Guysborough County |
|
|
|
|
|
Colchester County |
|
|
|
|
|
Pictou and Antigonish County |
|
|
|
|
General Information about Monilinia Blight and Management
It is important to monitor plant development stages in
your fields, especially if this disease has occurred in your fields previously.
I encourage growers to go out to the fields and see how floral buds are
developing.
When looking at fruit buds do not count obviously dead
fruit buds. To do that, you can walk your fields in a “W” pattern and collect
20-30 stems randomly. From those collected stems, count the total number of
floral buds and the number of buds at the F2 stage or beyond. You can simply
dive the number of F2 buds by the total number and times 100. This would you
the % of F2. Please don’t count obviously dead floral buds.
Figure 5. Wild Blueberry Floral Buds in F1 and F2 stages.
For monilinia to infect blueberry plants, there should
have mummy berry spores, blueberry buds at a susceptible stage (F2 and above)
and an infection period of long enough wet period and temperature. Only treat
for Monilinia when blueberry buds are at least at 40% and before the next
forecasted wet period.
For products to prevent monilinia infection, please
refer to Perennia’s updated pest management guide for wild blueberry (2022): https://www.perennia.ca/wp-content/uploads/2018/03/Wild-Blueberry-Pest-Guide-2022_FINAL.pdf.