Blackberry flowering

Blackberries are in full bloom or beyond at the Piedmont Research Station today. Here are some shots  taken from the RCA trellis plots. All cultivars have some flower kill as can be seen by the black dots in the centers of the flowers. Flowers with those blackened centers will not develop into fruit. We will take viable flower counts next week.

Apache

Oucahita

Von

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

Assessing Winter Injury in the Piedmont and Western North Carolina Class Exercise

Guest writer: Nicholas Basinger nabasing@ncsu.edu, Graduate Student, Department of Horticultural Science with data collection help from HS 422 class members. Edited by G. Fernandez

Deep cold, accompanied by snow came into the state the last week of January.  Some growers were reporting temperatures in the negative single digits.  After this weather came and went,  growers were wondering if the frigid air had affected their crops.

Samples of whole canes were collected from 3 locations: the Piedmont Research Station (PRS) in Salisbury, NC, the Upper Mountain Research Station (UMRS) in Laurel Springs, NC and a grower site located near Hendersonville, NC.  We looked at 4 varieties of blackberries and 3 varieties of raspberry.

These samples were brought back to NCSU and dissected on February 10, 2014 as part of a class exercise in HS 422, Small Fruit Production.  The objective of the exercise was to determine if bud damage had occurred due to the cold temperatures in the past few weeks. Three buds from an upper lateral, three from a middle and three from a lower lateral (see drawing below) were dissected and assessed for damage.

We observed the most injury in raspberry varieties from the UMRS (elevation 2800 ft), which saw temperatures of -9 ^oF during the late January freeze.  By the time the freeze hit on Jan. 30,  780 chilling hours had accumulated at this site. Previous days to the lowest recorded temperature were in the mid 40’s.  This is almost a 50 degree temperature shift in a matter of 2 days.   Raspberries do not tolerate large temperature fluctuations and are more susceptible to cold damage when their chilling requirements have been met.  Almost all of the raspberry canes at this site showed bud damage throughout the cane. Fortunately, the raspberries sampled were primocane-fruiting types and will be mowed to the ground in a few weeks. They will  produce a crop on the primocanes later in the summer.  

In all locations, we observed some injury to blackberry buds.  In general, injury was observed on buds furthest from the crown. And the colder sites, Hendersonville and Upper Mountain Research  Station in Laurel Springs had more injury than the Piedmont Research Station in Salisbury.

Below are some examples of what to look for when dissecting caneberry buds. 

The cold temperatures have permanently damaged this Navaho bud. Notice that in the center of this bud there is a dark dot (necrosis).  This will not produce fruit in the spring.  Photo: Gina Fernandez

This picture is a great example of healthy Navaho bud.  Notice that the bud looks green and there are no signs of necrosis. Photo: Nicholas Basinger

If you are interested in taking samples from your field, we suggest you sample an entire cane as is illustrated in the diagram above to determine where the injury has occurred. If the majority of the injury is on distal portions of canes and laterals, those buds can be removed by pruning. For more on how to sample read this posting: http://teamrubus.blogspot.com/2014/01/assessing-cold-damage-in-blackberry-and.html

ALSO, here is a link to an awesome (GF opinion) video, showing how to dissect and look at buds,  click HERE. When dissecting it is VERY important to cut down middle of the bud; if you do not cut down the middle you may not be able to see damage if there is some present. 

Buds look good!

Here are a couple of images that show buds that we looked at yesterday. As I mentioned before, buds are tight and at the stage when they should be most dormant.  We did not see any damage to all but one of the buds we evaluated (20+ buds).

The first image is of a healthy bud, this is typical of the many buds we sliced longitudinally.

This image was from Navaho, but all other cultivars including those from the Pacific Northwest looked healthy.

Red arrow points to healthy bud.

This is from a small weak lateral, cut from the tip of a plant:

Red arrow points to damaged bud.

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.

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.

Cold weather and blackberry and raspberry bud damage 2007

Blackberry bud damage in April 2007. Note that the primary buds were killed (browned leaves) and secondary buds growing (green leaves).

After an abnormally warm March, April is decidedly cooler in NC. Blackberry and raspberry plants have broken bud and many are beginning to flower. Temperatures are expected to be quite cool these next few days, with temperatures predicted to be 38F in Raleigh and 33F in the Asheville area according to Accuweather. So growers in western NC should be paying close attention to their weather this week.

Although we don't have data on critical temperatures for blackberry, we expect that damage due to cold would be very similar to strawberry. Tighter buds are less vulnerable, and open blossoms are the most vulnerable. These temperatures are:

Tight Bud: 22F
Popcorn stage: 26F
Open Blossom: 30F

Strawberry growers can use rowcovers or irrigation to protect open blooms. Blackberry growers do not really have these options. Rowcovers would be very difficult to spread over the rows. Overhead irrigation adds ice and therefore weight to the canes and will cause them to break.

We experienced a similar situation in 2007. There was lethal damage to primary buds. Fortunately, secondary buds broke soon after the primary buds were killed and the secondary buds produced approximately 70% of a full crop. Five to six weeks after the freeze, the secondary buds were open and you could hardly tell there was any damage earlier that year. Laterals were longer and harvest was later, I think it was at least 2 weeks. Given that we were early, this delay if it happens may not be a bad thing, we may  be able to reset our harvest to the normal dates.

For some insight into what happened in 2007, here is a link and some pictures.
http://www.ces.ncsu.edu/disaster/freeze/BlackberryRaspberryAssessment.pdf

There is also more information on strawberry protection and critical temperatures on the strawberry portal.
http://www.ncsu.edu/enterprises/strawberries