Flowers damaged by cold temperatures

Last week, in one of our research plots at the Piedmont Research Station in Salisbury, NC, I noticed that some of the flowers had tiny black centers. This is the result of cold injury to the flowers earlier this spring just as the buds were starting to develop (23F on 3/27/14). The flower in the oval on the left, with the green center will develop into a fruit, while the two flowers in the ovals on the right will not develop into fruit. There were not many damaged flowers and I expect that the total yield will not be impacted by the amount of damage in this picture.

Cane damage, what to do?

Protecting blackberries from winter cold with straw mulch. Photo credit: unknown at this time, will update when I figure out its origin.

This year we have seen damage to canes and buds....here are some suggestions on how to manage the crop for this upcoming growing season.

If you have CANE Damage:
First, determine extent of the injury to your canes.

If canes are completely killed to ground, remove them as they will be sites for disease infection. Once they are removed, you will need to manage the emerging primocanes. There will likely be lots of them and they will grow quickly.  Tipping may be needed more frequently.

If canes are damaged on the upper portions, remove the damaged portions, as they will be sites for disease infection. This is of course dependent on if you have labor and how much time it will take to remove the damaged portions of the cane.

If canes are damaged in spots, the plant will have reduced capacity to provide nutrients to the developing laterals, because of damage to vascular tisse (see figure 3 in the previous blog post). I talked to Dr. Bernadine Strik. OSU Berry Crop Extension Specialist,  and this was her suggestion:
" If canes or the bud base are damaged and there is lateral growth, these laterals may “collapse” – grow well and then wilt. While it’s hard to deal with bud base damage, if there is partial cane damage, foliar fertilization to support lateral growth with the cambium of the cane has time to repair can work. We have resisted putting specific recommendations of foliar feeding during delayed dormant and fruiting lateral development stages, because it would be possible to do “too much” and burn the young leaves. This would  be a concern. Also, foliar feeding will not “solve” problems with poor bud break or “fix” canes that are damaged. It’s not a miracle cure. With that said, if there is partial cane damage and the cane is thus limited on translocation of mobile nutrients, foliar feeding would help get  the laterals through the early development period. I would recommend a low foliar rate of N (e.g. 5% urea) as well as Ca. It’s hard to mix Ca with K, but K might be needed also (caution on not applying too high a rate as this will burn leaves). I would apply a foliar every 2 weeks until first bloom."

For management of diseases, make sure you stick to the recommended spray program and watch out for grey mold (botrytis).

Bud Damage:

We have had this occur in the past, both in 2007 and 2012. If only the primary buds are killed, there may be fruit produced from secondary buds. Here are some links to previous posts regarding bud damage:

http://teamrubus.blogspot.com/2012/04/freeze-2012-field-visits.html

http://teamrubus.blogspot.com/2012/04/cold-weather-and-blackberry-and.html

Blackberry Freeze Damage Sample Evaluation in Savannah

Growers and Agents: I will be at the 2014 Fruit and Vegetable Conference in Savannah, GA later this week. Debby Wechsler, Executive Secretary of the North American Raspberry and Blackberry Association is sharing her table space outside of the Blackberry and Raspberry Conference on Thursday afternoon, January 9, 2014.  I will be looking at blackberry bud samples that may be damaged by the cold temperatures over the next couple of days.

Please bring in your samples. I will have a microscope and some sharp scalpels to slice open the buds.

Protocol:

- take samples from laterals that occur at the top, middle and base of the canes. Bring in several buds from each section. 

-place samples in bags, make sure that the samples are labeled with top/middle/base of cane and variety. 

-below is an example of a bud, this was taken last spring so the buds are further along than what you may see in your field. 

-if you are doing it on your own, longitudinal slices are better. I suggest you go out before the temperatures drop and after as well, to see if there are any differences. 

RCA trellis with covers

RCA trellis with rowcover, Piedmont Research Station, Salisbury, NC. Photo: K. Snider. 

Blackberry canes with emerged buds, under rowcovers. Photo: K. Snider. 

At the Piedmont Research Station in Salisbury, NC, we have a set of four RCA trellises oriented  North/South and East/West. The primary objective of this project is to evaluate attributes of fresh blackberry fruit. We are most interested in the level of sun scald based injury to fruit based on canopy orientation.

However, the RCA trellis is used in colder regions of the country as a way to grow varieties that are not cold hardy. In North Carolina, twice in the past decade, we have experienced low temperatures (8 April 2007 and 12 April 2012)  that have resulted in significant crop loss. Developing flower buds and therefore the blackberry crop were killed by late season frost/freeze events. So, we are looking at this trellis system as an option for protection from cold in NC.

Temperatures at the Piedmont Research Station in Salisbury, NC, for the have been cold, 20F on 21 March. We had emerged buds so we protected blackberry plants under rowcovers. Although the buds would likely have survived, we wanted to protect them, just in case. We have data loggers recording temperatures under the covers and will download them next time we get to the field and update this post to include those temperatures.

Budbreak 2013

Black raspberry bud 14 March 2013. 

Navaho bud 14 March 2013. 

Prime-Ark 45 bud 14 March 2013

Von bud 14 March 2013

Budbreak on this first day of spring appears to be holding off due to the cooler temperatures we have been experiencing in NC. These pictures were taken at the Sandhills Research Station last week by my student, CM Bradish. Only Prime-Ark 45 is showing any signs of green leaves.

I was looking at the Team Rubus blog post from last year and see that in March (10th), at the CEFS pruning demonstration, blackberry buds were a bit tighter, but not much. http://teamrubus.blogspot.com/2012/03/pruning-workshop-at-center-for.html

No budbreak at this time is a good thing. We have accumulated plenty of chilling and once it gets warm, these buds will grow quickly. We don't need a repeat of 12 April 2012 when flower buds were killed by low temperatures. http://teamrubus.blogspot.com/2012/04/freeze-2012-field-visits.html

If you have time to take some pictures and send them to me (labeled with variety and date photo taken), it would be great to have a snapshot in time from various locations, to see how the crop is developing.

Gina_Fernandez@ncsu.edu

What to look for in terms of cold damage in blackberry and raspberry plants ALSO SEE POST 4/19/12

Image 1. Bronzed flower buds

Preliminary reports from across the state indicate that temperatures did go below freezing. It was 27 F in Davidson County,  and 29 F near Danville, VA.  To determine if your caneberry plants were damaged, you will need to wait a few hours. Around noon, go out to your field and start looking at your buds. Closed flower buds will show a bronzing on the sepals (green outer layer of flower buds) see an example in Image 1. However, there does not to be any visible damage, you need to look inside the buds.

Image 2. Blackberry flower bud after freeze injury. Note that only the ovaries and the receptacle are blackened. 

Slice the buds longitudinally and take a close look. In 2007 we saw that the male plant parts (anthers) were fine in some cultivars, but the female parts were damaged (ovaries) and the receptacle were damaged. See Image 2.

Image 3. Damage to blackberry buds in 2007, the entire flower, anthers, ovaries and receptacle are blackened, in most of these buds. 

However in some cases the entire bud was damaged as is shown in Image 3. In either case, no fruit will be formed.

In a few days you may see entire laterals wilting as was seen in the previous post. If you see this type of damage, you will loose the fruit from those buds. BUT you should see secondary flush of growth and based on what happened in 2007 you will get up to 70% of a full crop, later. Later in this year, means a normal fruiting season, I hope.

If you have damage, what should you do? With all the dead tissue, there is an increased risk of botrytis.  You should apply a fungicide to help keep the infection level down. Maintain your spring fertilizer regime and keep weeds under control to reduce competition for nutrients.