Bud removal to mimic freeze damage in the spring

This spring we set up demonstration trials at 2 locations in the state to monitor what would happen if we mechanically removed buds at critical times during flowering. We wanted to mimic what may happen when we get bud kill to flowers in the spring due to freezing temperatures. One of the trials is at the Sandhills Research Station in Jackson Springs, Josh Mays is overseeing the trial on the cultivar Ouachita. He removed buds at four times in the spring, has taken lots of data and lots of pictures. Here is a short video of what we saw today. He will be sharing more at grower meetings this upcoming year.

The other trial is at the Mitchem Farm in Vale NC. I'll post about that one later...

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. 

Assessing cold damage in blackberry and raspberry buds and wood at annual NC grower meeting

In early January, at the SE Vegetable and Fruit Expo in Savannah, GA, we set up a microscope and a magnifying glass (the kind you get in a craft store) to look at bud damage in blackberries. Most of the buds that I sampled looked good. http://teamrubus.blogspot.com/2014/01/buds-look-good.html

On Feb 6, 2014 we be looking at more samples at the annual meeting of the North Carolina Commercial Blackberry and Raspberry Association, in Shleby, NC. (Contact Daniel_Shire@ncsu.edu for meeting information). We will be looking at  samples collected  from our research blackberry and raspberry fields.

You are welcome to bring in some samples from your fields. We may not get to all of the samples, but we will train you to look at your own samples, so you can sample your own fields on a regular basis.

If you want to bring in some samples or prepare samples for evaluation at home, here is the protocol (courtesy of Michelle Warmund, University of Missouri):

• cut 3-4  8" cane sections from a low, mid parts of a main cane and some laterals from the fruiting area
• place each group of canes in  in a zippable gallon size plastic bag
• label each bag with name of cultivar and where the cane was taken from the plant (low, mid, laterals)
• store at room temperature for 4-5 days before the meeting.

At the meeting we will cut canes and check for injury symptoms. Dead cane sections and buds will have oxidized and turned brown after storage for 4-5 days in the zippable gallon size plastic bag. The sections from the lower and mid cane are needed to assess potential damage primarily to the canes. We will look at bud and cane damage on the laterals.

Here are some examples of bud and cane damage in West Virginia at the USDA Appalachian Fruit Research Station in Kearneysville, WV. The photos taken by Dr. Fumi Takeda.

Winter injury to blackberries. Plants with shriveled floricanes and primocanes are green and healthy. Photo: Fumi Takeda 

"Bark" scrapped off, showing oxidation of cambial/vascular tissues. Photo:Fumi Takeda

Primary bud is damaged as indicated by necrosis of partially differentiated inflorescence axis. Secondary bud is still undifferentiated, no sign of damage. Photo:Fumi Takeda.

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. 

Frost 2012 damage to blackberry crop

I was able to visit blackberry growers earlier this week in Western NC.  The current situation is very complicated. I saw a lot of flowers and buds with blackened centers (Figure 1). The center part of the female part of the flower, (technically the pistal), it is attached to the receptacle. Both of these flower parts form the blackberry fruit that we eat, and....both were damaged.

Temperatures. Temperatures dipped to 25-27 F degrees and stayed there for 4-6 hours depending on location the first night, but temperatures likely varied due to location as was evidenced in variation in the amount of damage we saw. (In 2007, it got to 20 F and was widespread across the entire state, damage was severe and killed the entire fruiting shoot).

Crop stage and location. According to most growers, the crop was about 2 weeks early, so all cultivars were well ahead of their normal schedule and many were flowering.   Natchez was at or near full bloom and Ouachita had some open flowers and many flowers that were at popcorn stage. Navaho was behind with just a few open flowers. However, these stages varied depending on the location of the field, location within the field (higher spots had less damage), and location within the canopy (upper wire had more damage than lower wire). 

Crop damage. Damage ranged from very little to severe depending on the location  and cultivar.  In some cases, just the king flower was dead (Figure 2). In other cases, flowers only in the upper portion of the canopy were damaged. I estimate that in some severe situations, there was 80-90% damage and in others only 30-40% damage. 

As I mentioned above and in earlier posts, the 2007 freeze killed the entire primary shoot and the secondary buds emerged and were able produce a crop. However, this year only flowers were damaged, the primary shoots are still viable and they will likely remain attached to the canes. This will likely inhibit the growth of the secondary buds and the crop that they would produce. 

Figure 1. Blackberry flower after 2012 frost. Photo courtesy of Amy Lynn Albertson.

Figure 2. Navaho fruiting shoot. Area circled shows king fruit dead, but subbordinate flowers are viable. 

What to do this year? There are a couple of options, these are some that come to mind at this time.

• You could just wait and see what happens, some buds lower on the primary shoot may not have sustained damage as is seen in figure 2. They will produce fruit, in general the tips of the shoots have the most fruit, often 3-5, while lower down the shoots, only one fruit per node is produced. 
• Prune off primary shoots. You would have to do this close to the cane, but be careful not to prune or damage the 2nd bud (leave approx 1/4 inch). This MAY allow the secondary buds to develop.
• Prune out the entire canes, removing all the dead flowers and the canes that they are attached to. 
• In all cases, maintain a fungicide program, in the first two scenarios, you will have more dead tissue out there that will be susceptible to disease infection.  

Future? Wind machines or helicopters may help if inversions are present. Helicopters or wind machines are often used in peach orchards and grape vineyards. When inversions are present these machines are able to mix the air,  bringing the warmer air down and mixing it with the cooler air, and keeping the temperatures above lethal stages. 

We are also evaluating a movable trellis. This trellis can shift positions. So when it gets cold, the trellis can be laid down and row covers can be placed over the entire row. Finally, we can hope that we are not 2 weeks early in the upcoming years. The earliness of this years crop really elevated the amount damage we saw.

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.