Small Fruit Class

Yesterday I finished teaching HS 422, Small Fruit Production. Throughout the semester I presented lectures on biology, production, pests and more of strawberry, blueberry, blackberry, raspberry, and other small fruits. For the 'lab' portion of the class, we took trips  to strawberry, blueberry, blackberry and muscadine farms. Some were small PYO and some were larger commercial operations. Growers in NC are great, they open thier farms, share their knowledge and welcome the next generation onto their farms. Thank-you students and Thank-you NC growers!

Estimation of damage from a grower and his daughter

Blackberry shoot about to be dissected

A grower in western NC sent me this information that he and his daughter gathered as part of a math lesson. They used real data from the plants that had been damaged from the cold temperatures in April. I have asked them to follow up with pictures and yield data. I will keep you all updated. I have also instructed some of you to do the same in your fields.

Blackberry Freeze Damage/Production Estimate

Conducted 4/24/12
Frost and Freeze occurred 4/12/12 27 degrees on top of field and 25 at bottom
Randomly selected one Navaho plant and removed every fruit shoot and sliced each fruit bud to determine percentage of live buds at this development stage of Navaho.
Marked the plant to later determine new shoot generation.
Plant utilized was a 3rd season plant ¾ up the knoll and mid field.
Data collected:
107 fruiting shoots on the plant.
10 minutes to remove all shoots – (approximately $3334 of labor to remove shoots per acre)
Average of 6 fruit buds per shoot at this development and time of season (there were 5 open blooms on the entire plant)
340 buds were determined “alive” out of 642 buds examined – 53%
These plants have been under a vigorous fertilization/irrigation regiment following the freeze – to hopefully stimulate new growth.
Observations made:
0 buds were found alive the day after the freeze.
The live buds appear to be the ones that have developed after the freeze. The live buds are small ones surrounding the top dead buds or developed at a lower lateral of the fruit shoot.
It appears that there is a possibility of further new buds to develop at lower tiers of the fruit shoot.
There is concern of deformed fruit on some buds that appear to be “alive.”
Natchez were much further developed and 0 to very very few new buds are being found.
The 1st year harvest Navaho appear to have a more significant new bud development – no data at this time.

If you would like some help estimating your damage give me a call or send me an email. This is not like the 2007 freeze, so any information you can share will help us all learn from this experience.

Another cold night in store for NC

Here is the latest from the National Weather Service, freezing temperatures and high winds are forecasted for the mountains of NC.

...WIND ADVISORY REMAINS IN EFFECT UNTIL 9 PM EDT THIS EVENING... ...FREEZE WARNING REMAINS IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM EDT TUESDAY...

* LOCATIONS...THE MOUNTAINS OF NORTH CAROLINA.

* HAZARDS...STRONG GUSTY WINDS AND FREEZING TEMPERATURES.

* TIMING...STRONG WINDS THROUGH MID EVENING. FREEZING TEMPERATURES OVERNIGHT.

* WINDS...NORTHWEST 15 TO 25 MPH WITH GUSTS UP TO 45 MPH AT TIMES.

* IMPACTS...LOOSE OBJECTS MAY NEED TO BE SECURED FROM GUSTY WINDS. DRIVING COULD BE DIFFICULT IN HIGHER GUSTS. A FEW WEAK TREES COULD BE BLOWN DOWN. DAMAGE TO SENSITIVE OUTDOOR PLANTS FROM THE FREEZE OVERNIGHT.

* TEMPERATURES...LOWS IN THE UPPER 20S TO AROUND 30.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND ADVISORY MEANS THAT WINDS OF 35 MPH ARE EXPECTED. WINDS THIS STRONG CAN MAKE DRIVING DIFFICULT...ESPECIALLY FOR HIGH PROFILE VEHICLES. USE EXTRA CAUTION.

A FREEZE WARNING MEANS SUB-FREEZING TEMPERATURES ARE IMMINENT OR HIGHLY LIKELY. THESE CONDITIONS WILL KILL CROPS AND OTHER SENSITIVE VEGETATION.

***From our experience last week, these predicted temperatures (high 20's) will only kill the flowers and flower buds, it takes colder temperatures to kill the shoots (low 20's).  High winds could also damage the plants, causing cane and shoot breakage and potential damage to the trellises. ***

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.

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).

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

Crop phenology, when things happen...

The southeastern US, like other parts of the country had a very mild winter. Many people are wondering if crops will be earlier than usual.  At this point blackberries and raspberries are a bit ahead of schedule, but we will not know until later this season, how far ahead of normal harvest will actually be, if at all. If you are a grower, you should have a notebook where you record dates of key phenological events. Some of these events are bud break,  bloom, primocane emergence, and harvest. Although at times it is hard to remember, this will help you determine when things happened in the past and will help you compare seasons and determine when fruit may ripen. I have included an example of 50% bloom and harvest dates for a number of cultivars. Although this technique is not foolproof it is a start and we hope to have more tools for you in the future to help you forecast harvest times for you. However, you will need the basic information that I listed above.

Flower buds on raspberry plant late March 2012

Here is some data from the University of Arkansas, showing bloom and harvest dates for a number of blackberry cultivars. The number of days from 50% bloom to peak harvest for Ouachita ranged from 43-61 days (yellow columns). This is quite a spread. While the number of days from first harvest to last harvest ranged from 34-41 days (blue columns). You can easily do the same.