Another year, another round of blackberry flower bud injury

Blackberry flower bud damage. The centers are the female part of the flower (a gynoecium with many pistals) develop into the fruit. Image above shows 3 out of 5 flowers with blackened centers, indicating that there was lethal damage and fruit will not develop.

Since 2007, just as the NC blackberry industry began to emerge, spring time cold temperatures have killed flowers multiple times (my blog says 2007, 2012, 2014, and 2018, but there may be more). 

Last week, just as we began to think we had missed any chance of bud injury, temperatures dipped to 27F or below.  Blackberry shoots with developing flowers were emerging. There was a wide range of damage, depending on location, degree of bud break, and temperature. Locations and cultivars on the same farm had  in some cases little or no damage to 40% damage to the primary flower buds. 

Growers know what to look for (blackened centers) and had been assessing their crop for the last few days. See image above. In most cases the king or largest flower bud was damaged and some of the secondary and tertiary flower buds also were damaged. The smaller flower buds with green centers will develop into fruit. 

When we see this type of damage, often there are secondary shoots that will emerge and produce flowers a week or so after the initial damage. Look for succulent lighter green often elongated shoots. (Sorry no image, if you have one, send it to me and Ill post it here). The extent of secondary shoot emergence is not consistent. It likely depends on extent of damage to the primary flower buds, cultivar, how well the secondary shoots had developed in the previous year.  We have done some shoot removal studies in the past. These will be summarized in an upcoming post.

Meanwhile here is a link to posts from the past on this topic.
https://teamrubus.blogspot.com/search?q=freeze+

Spring Caneberry Chores

Blackberry leaves and buds eastern NC April 3 2018.

Spring Caneberry (Raspberry and Blackberry) Chores 2018

Dr. Gina Fernandez, Small Fruit Specialist at NC State University

Spring 2018 has been cool, we had snow in Raleigh on April 7. But blackberry plants have broken bud are are ready to start the season. Chores and timing may be somewhat different in your area or for your cropping system.  For IPM recommendations and general production practices, see the 2018 Southeast Regional Caneberry Integrated Management Guide.

http://www.smallfruits.org/assets/documents/ipm-guides/Caneberry-Spray-Guide.pdf

The IPM guide above lists these stages of growth or planting age. This is the time of year we are now leaving (or have left a while ago!) the dormant period and by the time the next newsletter comes out, we will likely be harvesting in some locations.

Dormant (prior to budbreak)

Delayed dormant (swollen buds) to green tip

Shoots 6 inches long and before blooms open

Pre-bloom (when flower buds show white)

Early bloom (5-10%)

Full Petal

Cover sprays

Pre-harvest (14 days before anticipated harvest)

Harvest

The SRSFC production practices are in the Regional Caneberry Production guide (includes link to PDF format):

·      https://content.ces.ncsu.edu/southeast-regional-caneberry-production-guide

Plant growth and development

·      Plants deacclimate quickly

·      Bud differentiation (additional flowers can be formed)

·      Bud break

·      Flowering

·      Primocane emergence

Pruning and trellising

·      Finish pruning and make sure all floricanes are tied to the trellis before budbreak

·      Remove canes from field to minimize spread of diseases

·      Rotate shift trellises to horizontal position before budbreak; rotate to upright position immediately after flowering.

·      Prepare for flower to fruit monitoring (see http://teamrubus.blogspot.com/2015/03/monitoring-flower-to-fruit-development.html )

Weeds

·      Weed growth can be very vigorous at the same time as the bramble crop peaks

·      Weed control is best done earlier in the season, with pre-emergent herbicides before harvest commences

·      Hand-weed perennial weeds in and around plots

Insect and disease scouting

·      Growers with a history of cane diseases and/or mites often find that certain fungicides and oils are most effective just prior to bud break. The period of time in the spring when the plant is flowering is the most important season for control of insects and diseases. Know what your pests are and how to control them. See the

Water management

·      Test irrigation system and look for leaks

·      Canberry plants need about 1”-2” water/week. This amount will be especially critical during harvest

Fertlity management See Caneberry Production Guide

https://content.ces.ncsu.edu/southeast-regional-caneberry-production-guide/fertility-management

Marketing and miscellaneous

·      Service and clean coolers

·      Make sure you have enough containers for fruit in the coming season

·      Prepare advertising and signage for your stand

·      Contact buyers to finalize orders

·      Hire pickers

·      Prepare signage for field orientation; it is easier to tell pickers where to go if rows are numbered

·      Check buds and canes for cold damage (27°F is temperature that kills all stages of flower buds see http://teamrubus.blogspot.com/2016/04/damgage-to-blackberry-flowers-at-27f.html

·      Monitor and record peak flowering date for each variety every year. Then later during harvest, check your records for peak harvest of each variety.  Over time, it will help you to determine when your peak harvest will occur.