Mississippi Vaccinium Journal for July-Aug 2015

The latest edition of the Mississippi Vaccinium Journal is now available. In this issue topics include a new survey on mechanical harvest, fruit splitting, careful use of herbicides, insecticides and rain, an upcoming GAP/GHP workshop opportunity, a few photos of the Blueberry Jubilee, and Road Trip! MS blueberries go to India.

Download the newsletter here in PDF format: Mississippi Vaccinium Journal volume 4 issue 3

As always you can access this issue and all past issues at http://msucares.com/newsletters/vaccinium/index.html

If you have any suggestions, questions, or feedback please feel free to contact me!

Netting Grapevines Against Birds

Last year I had problems with birds destroying some grapes before I had the chance to harvest them (full disclosure: I had several conferences last year that I attended while it was close to harvest time.  I rolled the dice that the fruit would still be there when I got back — no such luck). This year I am taking no chances!  Last week the bird netting went up on two of the four rows in the vineyard and this week the other two will be covered as well.  Since the vineyard is so small, it was relatively easy to put the netting over the rows and secure it.  Below are a few photos (taken by Richelle Stafne) of the process.

Throwing the netting over the row.  It helps to be tall.

Throwing the netting over the row. It helps to be tall.

Pulling the netting over the vines to make sure it covers the canopy.

Pulling the netting over the vines to make sure it covers the canopy.

Securing the netting by using zip ties. Other materials can be used such as string, twine, or bread ties. The netting was tied to the irrigation wire with the zip ties.

Securing the netting by using zip ties. Other materials can be used such as string, twine, or bread ties. The netting was tied to the irrigation wire with the zip ties.

The job is finished and we admire our efforts while sweating in 90+F heat and humidity.

The job is finished and we admire our efforts while sweating in 90+F heat and humidity.

The netting will remain on until harvest.  Once all fruit is harvested it will be removed and stored for next year.  Netting is an added expense to the vineyard and it makes management more difficult, but it is a necessity to protect the fruit from birds. There are different kinds of netting, some will last longer than others (and hence are more expensive), so it depends on an individual managers needs which kind to purchase.  Tractor implements are available to help with this process in large-scale operations.

Follow-up on White Drupelets in Blackberries

Yesterday I posted on why white drupelets occur in blackberries.  Well, the “why” that we know or think we know.  I also looked at the genetic make-up of certain cultivars.  Today, I went into the blackberry plantings here in Poplarville looking for white drupelets.  Since the season is almost over on some cultivars it wasn’t easy — there just weren’t enough berries, but I did find a few.  I was able to find them on ‘Ouachita’, ‘Kiowa’, ‘Chickasaw’, and ‘Sweetie Pie’.  I took some data on it too.  I harvested all the berries I could find that had white drupelets.  I counted the number of berries for each cultivar and from each berry counted the number of white drupelets.  I got an average and a range.  Plus, I took Brix measurement of the sugar content in the white drupelets compared to normal drupelets (I only did this for ‘Sweetie Pie’ because it was the only one that had a large enough sample).  Below is what I found:

Cultivar     # of berries    Avg. # white drup.    Range    Brix (white) Brix (normal)

‘Ouachita’       2                          2                   1-3

‘Kiowa’            5                          4.4                1-13

‘Chickasaw’    6                           2.7                1-9

‘Sweetie Pie’   45                         2.9                1-17        3.9             10.2

You may recall from yesterday that I broke down the genetic components of ‘Apache’ and ‘Kiowa’.  I will do that again for those I looked at today.

Ouachita:

Thornfree 25%, Brazos 25%, Darrow 17.1875%, OP (unknown) 18.75%, SIUS 68-1-8 12.5%, and US 1482 1.5625%

Kiowa:

Brazos 50%, Thornfree 18.75%, Darrow 12.5%, Wells Beauty 12.5%, and Brainerd 6.25%

Chickasaw:

Darrow 43.75%, Brazos 31.25%, Thornfree 12.5%, and Wells Beauty 12.5%

Sweetie Pie:

Brazos 43.75%, Humble 25%, Thornfree 18.75%, and Darrow 12.5%

As you can see ‘Brazos’, ‘Darrow’, and ‘Thornfree’ are mixed up in all of these cultivars.  Clark and Moore (2005) report that ‘Ouachita’ had low to no incidence of white drupelet in Arkansas. It has 25% ‘Brazos’ compared to ‘Kiowa’ at 50%, ‘Sweetie Pie’ at 43.75%, and ‘Apache’ at 31.25%. It appears likely that ‘Brazos’ has a role, but the extent is unknown. The field data doesn’t really tell us much because of the lack of replication and the few number of data points.  But with more it may be able to narrow down the genetic culprit of white drupelet.

The sugar content of the white drupelets was substantially lower than normal drupelets.  To me this suggests that the sugar may have not been there to begin with.  The texture and thickness of the skin are different than normal drupelets. At what stage does the drupelet abort from normal development?  This type of thing would be very difficult (or impossible) to replicate in a controlled environment.  I will continue to look at this issue and perhaps do a more in-depth study next year.

Below are some ‘Sweetie Pie’ fruit with white drupelets.  Just because it had the most white drupelets of the cultivars I looked at, it should not be an indictment of this cultivar.  It is later ripening that the others and thus had more fruit to sample.

'Sweetie Pie' fruit with white drupelets

‘Sweetie Pie’ fruit with white drupelets

Clark, J.R. and J.N. Moore. 2005. ‘Ouachita’ Thornless Blackberry. HortScience 40:258-260.

The Problem of White Drupelets in Blackberries

It is June, the month for harvest of blackberries in many areas.  Unfortunately, along with ripe fruit we also see other problems crop up.  This year I have seen pollination problems due to rain, SWD damage, stink bug damage, cane borers, anthracnose, and white drupelets.  So, what causes these white (or tan) colored drupelets? For quite some time no one knew what caused it (and we probably still don’t with 100% certainty).  Early theories revolved around insect damage (stink bugs, mites) or sunscald.

There are some very good descriptions and photos on the Team Rubus blog out of NC State and the UC IPM website.  I would encourage you to visit those sites.  Below is a photo of the problem in case you are not familiar with it.

White druplets on blackberry fruit

White druplets on blackberry fruit

The University of Arkansas-released cultivars Apache and Kiowa are most often mentioned as having this problem.  I would say that Apache has it most prominently.  Both the NC State and UC websites talk about the environmental conditions that contribute to this abiotic condition (abrupt increases in temperature, wind, low humidity) in concert with UV-radiation on the drupelet. The descriptions also talk about “tolerance” to the condition.  That would imply a genotype x environment interaction.  Since certain cultivars exhibit worse symptoms than others there is a genetic component that might be able to be exploited to reduce this problem in future cultivars.  But do we understand fully where it comes from (who is the offending progenitor)?

I broke down the parentage for both ‘Apache’ and ‘Kiowa’ to look for common ancestors.  The percentages are below:

Apache:

Thornfree 31.25%, Darrow 31.25%, Brazos 31.25%, Merton Thornless 4.6875%, and Eldorado 1.5625%

Kiowa:

Brazos 50%, Thornfree 18.75%, Darrow 12.5%, Wells Beauty 12.5%, and Brainerd 6.25%

Both of these cultivars have ‘Brazos’ in a significant portion of their parentage (>31.25%).  ‘Thornfree’ (US 1410 x US 1414), ‘Brazos’ (F2 of ‘Lawton’ x ‘Nessberry’), and ‘Darrow’ (NY 15826 x ‘Hedrick’) are in both cultivars and make up a large portion of their genetic makeup.  ‘Eldorado’ also is on both sides, but in a very small percentage (‘Eldorado’ is a parent of ‘Hedrick’ which is a parent of ‘Darrow’).

Now, this doesn’t get us to the answer — more analysis and experimentation needs to be done — but it seems likely that one of these three (or perhaps more than one) has lent genes that result in white drupelet.  Looking at the pedigrees along with real world, in-field data, would narrow it down farther yet.  We don’t know what the factors are that lead to the condition — skin thickness? pigment stability? These are possible hypotheses to follow up on.

With the warmer earth we are experiencing, it seems likely that this problem will continue to manifest in many growing areas.  New selections are being looked at to reduce this problem, but it may not be entirely eliminated.

Anthracnose on Bunch Grapes

More rain is falling today and is expected for the next few days.  All this wet and cooler weather creates good conditions for anthracnose infections.  Anthracnose (Elsinoe ampelina) can be severe in years with heavy and consistent rainfall (like this year).  Optimal conditions for disease development are in the upper 70s F.  The spores are splashed from plant to plant by rain.  It is seen most commonly on young, succulent green shoots and leaves.  The lesions are sunken on shoots and on leaves the leaves can be distorted and have a shot-hole appearance.  A photo of the disease on a ‘Victoria Red’ cluster is below.

Severe anthracnose infection on Victoria Red grape cluster

Severe anthracnose infection on Victoria Red grape cluster

How can anthracnose be controlled?  If you are in the Deep South, not too easily, I’m afraid.  Sanitation can help (get rid of infected plant parts).  Canopy management that promotes sunlight penetration and good airflow can also help.  But likely the best way is a dormant fungicide spray or two of lime sulfur followed by subsequent fungicide applications until veraison. More in-depth information can be found here:

http://www.smallfruits.org/smallfruitsregguide/Guides/2015/BunchGrapeSprayGuide2015.pdf

Fruit Splitting in Blueberries

The prodigious and regular rainfall we have experienced this Spring may be good for some things, but it is not good for ripening blueberries.  As you can see in the photo below, excess rainfall can cause blueberry fruit to split rendering it unsaleable and inedible.

Split Blueberry Fruit

Split Blueberry Fruit Caused by Excess Rainfall

So, how does this happen?  First off, water splitting happens in other fruits too.  More study has been done on cherries than most other fruits.  Reasons that cherries split are related to cultivar, fruit maturity, temperature of the water that hits the fruit, temperature of the fruit itself, duration of wetness, sugar content, fruit firmness, turgor pressure within the fruit, relative humidity, soil moisture, permeability of the skin and elasticity of the skin.  In blueberries, studies have shown that absorbed water through the skin is one reason, but also via root system uptake (although less so than direct contact).  The incidence of rain-caused splitting is very cultivar dependent and that cultivars with firmer fruit may be more susceptible to splitting.  What, within the fruit itself, could lead to this?  Some studies have suggested that in some cultivars the amount of air-filled spaces between cells could allow more water to enter but not split.  Another stated that cells that weakly adhere to each other may split more readily. A recent study showed that there is a moderately high heritability for fruit splitting, suggesting that this trait can be improved to some degree through plant breeding.

A past survey of MS and LA growers found that fruit splitting could reduce marketable yield by as much as 20% in some cultivars.  This means that cultivar choice is very important to avoid this type of damage.  Results from different studies mostly agree on results of what cultivars split more than others.  Below I have put them into three different categories: ~10% split or less (Low); ~10-19% (Moderate); ~20+% (High).

Low: Alapaha, Austin, Premier, Magnolia, Jubilee

Moderate: Gulf Coast, Chaucer, Columbus, Powderblue, Ochlockonee, Vernon

High: Brightwell (there was discrepancy on this cultivar, but 2 of 3 studies showed it to be high), Climax, Tifblue, Pearl River

One study found that excluding rainfall from the plants (covering them) was not a sure way of eliminating split, although it did reduce it.  Also, fruit on plants that are overhead irrigated appear less likely to split than those on drip irrigation.  New products are now on the market that may help reduce fruit split damage. They have not been tested in Mississippi, but have been tested in Florida and Georgia with encouraging results.

For further information you may refer to the papers below:

D. Marshall et al. 2008. Blueberry splitting tendencies as predicted by fruit firmness. HortScience 43:567-570.

D. Marshall et al. 2007. Laboratory method to estimate rain-induced splitting in cultivated blueberries. HortScience 42:1551-1553.

D. Marshall et al. 2009. Water uptake threshold of rabbiteye blueberries and its influence on fruit splitting. HortScience 44:2035-2037.

D. Marshall et al. 2006. Splitting severity among rabbiteye blueberry cultivars in Mississippi and Louisiana. Intl. J. Fruit Science 6:77-81.

D.S. NeSmith. 2005. Evaluation of fruit cracking in rabbiteye blueberry germplasm. Southern Region Small Fruit Consortium Research Project Progress Report.

M. Dossett and C. Kempler. 2015. Heritability of fruit splitting tendency in blueberry. HortScience (in press) abstract.

Popcorn Disease of Mulberry

Popcorn disease of mulberry is caused by a fungus (Ciboria carunculoides).  It occurs in late spring and early summer.  The white mulberries are more susceptible to this disease.  The disease manifests on the developing carpels and looks like popcorn kernels.  It is a serious disease if the tree is being cropped for commercial purposes; however, it does no harm to the overall health of the trees, thus homeowners do not need to worry (if the tree is only used for ornamental or shade purposes). So, if this disease does occur what can be done to stop it?  Sanitation is a good first step — clean up any infected material and remove it from the area where the tree is growing.  There is very little else a homeowner can feasibly do to reduce the disease.  Spraying the tree with Bordeaux mixture may help too, but getting coverage over the entire tree may be problematic. As with many fungal diseases, the severity will depend on the environmental conditions from year to year.  Some years will be worse than others.

Popcorn Disease of Mulberry

Popcorn Disease of Mulberry

If you wish to read more on this particular disease, Texas A&M has a good, short fact sheet on it here.

MidSouth Grape

I have been intrigued by the ‘MidSouth’ grapevine growing in my vineyard; enough so, that I tracked its entire pedigree down to the species level.  Here is what I found:

50% Vitis champinii

37.89% Vitis vinifera

5.08% Vitis rupestris

4.69% Unknown (probably V. vinifera and V. rupestris, but could not confirm)

1.56% Vitis berlandieri

0.78% Vitis lincecumii

It is an intriguing vine — moderately vigorous with moderate crop load.  Fruit set was very good this year and it is early compared to the other grapes I have in the vineyard.  Last year it had a distinct “raspberry” flavor, but I want to replicate that again in my mouth before declaring it as a consistent trait.  It is somewhat susceptible to anthracnose (caused by Elsinoe ampelina), as you can see in the photo below. ‘MidSouth’ has its faults — relatively low sugar levels, higher than desired acid, seeded, disease susceptibility, etc., but overall it is a cultivar with an interesting background.

Developing 'MidSouth' cluster in early May2015

Developing ‘MidSouth’ cluster in early May2015

Be Careful Using Herbicides

Glyphosate (i.e. RoundUp) has been getting a lot of bad press lately, mainly as it relates to GMOs.  This post is not about GMOs, but rather prudent use of herbicides. Herbicides are great tools, but must be used with caution. First of all, the label is the law, so any instruction supplied on the side of the herbicide container is what one must follow for application (an online version of the label IS NOT considered to equivalent to the actual one on the container).  Second, make sure the tanks you use are either dedicated for the type of pesticide being applied (one for herbicides, one for insecticides and/or fungicides, etc.).  Third, clean out the tank, especially if you are changing products.  Residue can lead to unintended consequences.  Fourth, understand the mode of action and rotate chemistries to reduce the chance for weed resistance. Fifth, know which weeds you want to control and use the best product for those weeds.  Sixth, timing of application is VERY important for control — knowing the weed life cycle and timing the herbicide application with the most vulnerable period will yield the best results. There are some rules to follow when using any herbicide, but since glyphosate is so ubiquitous some closer scrutiny is needed.

Now, on to glyphosate specifically.  It is a systemic herbicide, meaning the product is taken up by the plant and translocated within it.  Glyphosate inhibits plant enzyme production, thus disruption its ability to synthesize certain amino acids.  So, it is very good at killing a broad spectrum of weed species.  Unfortunately, if not applied properly, it can be very good at killing fruit and nut plants too.  Since RoundUp went off patent, there are many glyphosate products on the market now.  Some have very different percent active ingredient.  Knowing the percent active ingredient will tell one how much water to mix it with prior to application.  Still, sometimes errors are made and a high price is paid.

A recent visit I had to a blueberry field revealed significant damage from glyphosate application.  The grower had good intentions and had used glyphosate without problem for years, he had run out of one container and switched to another new one.  Several rows had no problems (application with the first container), but the next rows had significant death.  Why? The amount of active ingredient was different, but the applicator mixed the same amount for application.  The plants may never recover and probably need to be removed.  The photo below tells the story.  If in any doubt about applying herbicides properly, contact a local county Extension office for help.

Herbicide damage to blueberry plant

Glyphosate herbicide damage to blueberry plant

Flea Beetle Damage in the Vineyard

Flea beetles are an early season pest in the vineyard.  Both the adults and larvae are present during the Spring.  The best time to control this pest is at bud swell, as if not controlled they will continue to cause problems later as larvae.  Several products can be used to control flea beetles in the vineyard, such as Sevin, Danitol, Baythroid, etc.  See the photo below for the kind of damage the larvae can inflict on leaves (but also blooms).  Adult beetles will feed on swelling primary buds, and this is the more serious type of damage that occurs.  If this is a problem, they should be controlled to prevent a reduction in shoots (and crop) in the following years.

Flea beetle larvae feeding damage

Flea beetle larvae feeding damage