Highbush Blueberry Blog - Rachael Cheverie, Horticulturist

Thursday, June 23, 2011

As most of you may know I am currently on Maternity leave from AgraPoint but will try to post some updates to this blog throughout the growing season. You will notice that there is a place for comments below and we would love to have this become a forum for you the growers to exchange information and ideas on blueberry production in the province!

It’s been a cool and wet spring and we suspect that things are a week or two behind however if summer ever decides to make an appearance and stick around, things should start to happen pretty fast! The bushes in my backyard are just starting to bloom, but I suspect in warmer areas like the Valley, things are well underway! With all the rain we’ve had, irrigation is probably the furthest thing from your mind however, you may need to start irrigating if conditions change! Drought prior to harvest can result in reduced blueberry size and yield and drought later in the season can affect bud set for next years crop. Highbush blueberries require 1-1.5 inches of water per week and are susceptible to drought stress so maintaining a good 6 inch layer of mulch around the base of each plant is recommended!

It’s time to get supplies for monitoring blueberry maggot –yellow sticky cards and an ammonium acetate bait! The traps should be placed along field borders to catch incoming flies from hedgerows and wild blueberries nearby, as well as in the middle of the field to catch resident populations. As a general rule, pesticides should be applied 7-10 days after the first adult is caught on the trap to prevent egg laying in fruit. You generally start to see the adults emerging when the berries reach the ‘fruit colouring’ stage however, it’s best to have all the traps in place at the green fruit stage just in case the adults are early. The traps should be placed in the top third of the bush without touching any of the foliage. It’s important to have the correct identification of flies as there are several species that look similar and are attracted to the ammonium acetate bait. Blueberry maggot flies have a distinct M shape on each wing – please click on the Omafra Blueberry Maggot Factsheet to see a comparison of the various fly species wing patterns.

In general, diseases thrive in wet cool conditions and if you had been following John Lewis' posts to this blog, you will know that there were quite a number of infection periods this spring. It’s a bit too late to protect for this disease now but never too early to plan for next year, especially if you have had a problem with monolinia this year!

Other diseases to be concerned with include Anthracnose or ‘ripe rot’ which may attack twigs, blossoms, leaves and fruit and the canker diseases such as Godronia (Fusicoccum) and Phomopsis.

Anthracnose overwinters on the blighted twigs and spores are released during wet periods throughout the season. The greatest losses occur with wet conditions during bloom and at fruit ripening. Fungicides should be applied at various stages throughout the season and it’s important to remove any diseased twigs and increase air circulation through regular pruning. Godronia spores are released throughout the growing season and cankers can form on the 1-2 year old canes. Reddish brown cankers form at the bud scale and fruiting bodies form in the canker, during the summer serious infections can cause a wilt symptom with reddening of the leaves. The best way to control Godronia is through pruning and you also may get some prevention with the application of Bravo for Anthracnose. Phomopsis cankers can occur on 1-3 year old canes and causes a sudden wilting and death of canes during the growing season. A canker is often present at the base of the can and can be difficult to distinguish from Godronia. Plants that are wounded mechanically or damaged by freezing are more susceptible. It’s important to always have diseases identified properly to ensure the right course of treatment!
For more information on Godronia and Phomopsis and a host of other diseases please check out the Michigan State Extension blueberry site.

There have been two new herbicides registered for highbush blueberry production since last season, Select EC and Dual II Magnum. You can find the labels for both of these products and every other product registered in Canada on the PMRA Website.
For the most up to date list of products registered for Highbush Blueberry Production please see the newly revised Highbush Blueberry Insect and Disease Management Schedule and the Guide to Weed Management in Highbush Blueberry .

Please feel free to post comments here or send me an email (r.cheverie@agrapoint.ca) with anything you would like to see covered in this blogpost throughout the season!

Rachael Cheverie, Horticulturist, AgraPoint

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