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

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.

Blackberry plants recovering after the freeze 2007

Image 1. This is a secondary bud that has emerged (semi vertical green stem). There is a remnant of primary stem, it is the brown nub on the right. 

Image 2. Regrowth of laterals after complete loss of primary buds in 2007. 

Reports are in, there was damage, laterals were wilting in the afternoon at some locations after the  freeze this morning and at other farms there was just bud damage (4/12/12).

Above are some images of the plants a couple weeks after the freeze in 2007. These were in a field  of Arapaho. The remnants of the primocane leaves are on most nodes, it is the brown nub on the right side of the node (Image 1).  A few days after the freeze I was in this field and noted 99% blossom kill and most of the fruiting laterals tissue appeared dead (wilted). I did not look for secondary buds at that time. However, about 2 weeks later, secondary buds were emerging, and I could not find the dead primaries (Image 1).

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