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

Ambrosia Beetles Found in Muscadine Vines

Now muscadine growers have a new pest to concern themselves with in south Mississippi.  Recently, Chris Werle (USDA-ARS Thad Cochran Southern Horticultural Laboratory Poplarville, MS) found ambrosia beetles attacking muscadine vines.  These beetles are extremely harmful to the plants they attack.  Not only do the beetles attack the plant, but they also transmit a fungus (e.g. Fusarium spp.) that can eventually take down the plant.  Infested plant parts should be removed and destroyed.  Plants showing heavy infestation and/or significant related disease symptoms should be removed to halt further spread.  Control must be done before the beetle burrows into the plant.  The two links below have suggestions as well as photos of the pest.

North Carolina State University http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note111/note111.html

Clemson University http://www.clemson.edu/cafls/departments/esps/factsheets/turforn/ambrosia_beetles_to22.html

Below are some photos from Chris Werle of ambrosia beetle damage on muscadine and fig.

Ambrosia beetle damage on fig. Notice sawdust from boring hole

Ambrosia beetle damage on fig. Notice sawdust from boring hole (Photo by Chris Werle)

A trunk of a muscadine vine heavily infested by ambrosia beetle. Notice the many entry holes. (Photo by Chris Werle)

A trunk of a muscadine vine heavily infested by ambrosia beetle. Notice the many entry holes. (Photo by Chris Werle)

Ambrosia beetle damage on muscadine vine cordons.  Diagnostic "straws" of sawdust indicate the presence of the insect. (Photo by Chris Werle)

Ambrosia beetle damage on muscadine vine cordons. Diagnostic “straws” of sawdust indicate the presence of the insect. (Photo by Chris Werle)

Kiwifruit in Mississippi: Feast or Famine?

Most of us have seen kiwifruit in the grocery store and have even eaten it sometimes.  The bright green flesh with the black seeds and fuzzy exterior all make for a strange looking fruit.  That species of kiwifruit is Actinidia deliciosa. This species is the most commercial, but also has difficulties growing in temperate climates.  It is not especially cold hardy, has a moderate chilling requirement, and requires a very long growing season.  Other species have been used to overcome some of these obstacles — such as Actinidia chinensis .  Auburn University has done considerable work to develop new kiwifruit cultivars from this species. The USDA-ARS in Poplarville is trialing some of these cultivars now, but it will be a good bit yet to know any results as the vines are still very young.  A couple problems have cropped up though — vines die for unknown reasons and pollination has not been great (low fruit yields).  Time will tell if these are isolated problems or long-term issues.  Auburn has a Kiwifruit Production Guide.  Below are some photos of Kiwifruit at the USDA-ARS station in Poplarville, MS (from summer 2014).

Vining growth of a vigorous female kiwifruit plant

Vining growth of a vigorous female kiwifruit plant

Developing kiwifruit

Developing kiwifruit

Although we don’t know a lot about how this fruit will do in Mississippi, other states like Alabama and Georgia have begun to explore planting this fruit in larger quantities.  It will certainly be interesting to see how the market develops over the next few years.

April-June 2015 Issue of Mississippi Vaccinium Journal

The new issue of the Mississippi Vaccinium Journal is now available. Inside are articles on southern blueberry pollinators, a visit with Dr. Scott NeSmith from University of Georgia, and resources from recent meetings.  As always you can see past issues here: http://msucares.com/newsletters/vaccinium/index.html

If you wish to receive it directly via email, then email me and I will add you to the list.  Click the link below to access the current issue:

Mississippi Vaccinium Journal Vol 4 Issue 2

Beware Buying Fruit Plants at the Big Box Stores

I only write this as a public service message.  Don’t get me wrong, I am not necessarily blaming big box stores for their inventory.  I don’t know how some of the varieties are chosen and how they are labeled, but the consumer must be wary when shopping at these locations.  This past weekend I visited a big box store for a few items I needed.  I didn’t need any fruit plants, but I decided to take a look at what was available.  Needless to say, I was dismayed at the selection.  Where do I begin?

Available grape vine varieties: Concord, Flame Seedless, Black Monukka, Mars, Thompson Seedless.  Problem: All of these are not resistant to Pierce’s Disease and will die within a couple of years at most. There were no muscadine varieties available at this location in south Mississippi.  It boggles the mind. Solution: Do some serious research before buying grapes in the Deep South. Muscadines are the best option.  Some bunch grapes do have potential, but are not usually very common in the nursery trade.

Available blueberry varieties: Legacy, O’Neal. Problem: There is no problem with these per se, except that one was mislabeled as a rabbiteye variety (Vaccinium virgatum) and the other a wild blueberry species (Vaccinium darrowii) when they are actually southern highbush (Vaccinium spp.).  I did not see any rabbiteye varieties (although I did not look at every plant).  Rabbiteye varieties are the best option for a homeowner here.  Solution: Southern highbush blueberries are partially self-fertile but will do better with a pollinizer.  Rabbiteye varieties require planting two different varieties with overlapping bloom times.  None of this information was available on the labeling at the store.  Local nurseries will have a better selection.

Available pecan variety: Elliot. Problem: There were two tags on the tree.  One said ‘Elliot’ pecan and the other said “ungrafted seedling”, which means it is NOT Elliot, but seedling of Elliot. This is very misleading.  Someone thinking they were getting an Elliot may end up disappointed.  A seedling of Elliot may or may not have some of the Elliot traits that make it desirable to grow.  Pecan trees also need to have two different varieties with overlapping bloom periods in order to produce nuts.  In this case there was only one type available. Solution: Local nurseries may not have the best selection.  The internet is your friend in this case.  Most pecan trees come from AL, GA, or TX, although if you search hard enough you can find some in MS.  A homeowner should choose varieties that are resistant to pecan scab.  If you don’t and do not plan to control the disease, it is really a waste of your time, money, and effort.

Available bramble variety: Boysenberry. Problem: Boysenberry is a hybrid raspberry x blackberry cross that originates from the west coast of the U.S. and is not especially tolerant of high heat conditions.  Coupled with the high humidity and prodigious spring rainfall it is a recipe for poor plant production.  It was also mislabeled as Rubus ursinus. Solution: Many blackberry varieties are available that will grow and produce in the Deep South.  Raspberries fair less well because they too do not tolerate the heat as well as blackberries.  I have seen blackberry varieties available at local nurseries recently, namely Kiowa, Apache, and Brazos (!).  These are far better options than Boysenberry in our area, although the thorny types will have problems with rosette (double blossom) fungus.

There were probably other fruiting plants that I didn’t look at too closely at to see if there were problems with them as well.  The real lesson here is this:  Know what you are looking for and why.  Realize that all blueberries or grapes or pecan are not created equal.  Some do well here and some do not.  Mislabeling is not a new thing in the nursery trade, but seeing the grievous errors in these examples made me cringe.   Before buying at the big box store near you, educate yourself on the crop you wish to purchase, talk to the folks in the garden center, and if you are not satisfied go somewhere else.  Contact your local county Extension office for more information on fruit crops for your area.  Or feel free to contact me.  I can help.

Pecan Budbreak: The Last Holdout

Pecan trees are really attuned to the continental climate we experience in the middle of the U.S.  They are almost always the last tree to break bud in the spring.  Why is this? Dr. Darrell Sparks from the University of Georgia published a study back in 1993 that suggested both chilling and heat accumulation were responsible for budbreak timing in pecan (The link to the paper is here).  Below is a short description of pecan budbreak that I wrote for a conference back in 2007:

“Pecan trees, like most temperate fruit species, exist under a physiologically mandated rest period.  This rest period, also called dormancy, helps to regulate the timing of budbreak. The start of dormancy generally begins in late summer when shoot growth stops and apical dominance ceases.  Amling and Amling (1980) stated that rest is a growth-inhibiting physiological condition that can develop internally in buds.  The rest period can be satisfied by the exposure of buds to periods of cold temperatures.  Temperature, as well as hormones such as abscissic acid largely control the activity of the buds along with light intensity and day length (Nesbitt, 2002).  The hormone levels that induce dormancy dissipate during the process of chilling accumulation which generally occurs when temperatures are below 45 F, but above 32 F.  After the required number of chilling hours have been met (and this varies among cultivars and genotypes), an accumulation of heat over time will activate the buds and growth will begin again.  The in-between period when chilling has been satisfied, but heat accumulation has not been met, is known as quiescence.

Budbreak during the spring is closely associated with the chilling requirement.  Trees with a long chilling requirement will normally begin growth later than trees with a short chilling requirement. Budbreak regulation by heating and chilling is an evolutionary survival mechanism  derived through adaptation resulting in pecan being native throughout a large area of the United States.  In cold winter regions the high chilling received in the winter enables buds to break with minimum heating in the springtime.  Growth commences within a short period of time, thus increasing the probability that the fruiting cycle will be completed within the abbreviated growing season associated with cold areas.

Conversely, pecans are one of the most adapted plants to the southern U.S. because they have a relatively low chill hour requirement, but a high heat unit requirement. However, there are some cultivars that break bud very early which increases the danger of bud damage to spring frost (Nesbitt 2002).  The lack of a mandated chilling requirement contributes to pecan’s survival in regions with little or no chilling (Sparks, 2003). In these cases, the dormant period is prolonged in the absence of chilling temperatures; however, a deficiency of chilling temperatures can delay foliation, increase fruit drop, and reduce yield when pecans are grown in warm climates that lack sufficient chilling hours (Smith, 1994). The need for greater heat unit accumulating temperatures delays budbreak and minimizes the chance of damage from late spring freezes (Smith et al. 1992).  The mechanism of increased heat unit accumulation is evident in the southern U.S., where pecan is one of the last deciduous tree species to breakbud in the spring (Sparks 2005).

Budbreak in pecans is described as being under the interaction of chilling and heat accumulation.  Problems begin when sufficient heat is accumulated for the re-initiation of growth, leading to budbreak, in early spring when the chance of cold weather and damaging frost conditions has not yet passed.  The typical continental climate that exists in the Southwest, with wildly fluctuating winter temperatures, can pose a threat to those pecan trees that awaken from their quiescent phase and initiate budbreak because the heat requirement has been satisfied.

 Literature cited

Amling, H.J. and K.A. Amling. 1980. Onset, intensity, and dissipation of rest in several pecan cultivars. J. Amer. Soc. Hort. Sci. 105:536-540.    

Nesbitt, M. 2002. The pecan tree in winter. Pecan South 34(12):4-5.

Smith, M.W. 1994. Freeze injury to pecans. Proc. 28th Western Pecan Conf. pp. 155-157.

Smith, M.W., B.L. Carroll, and B.S. Cheary. 1992. Chilling requirement of pecan. J. Amer. Soc. Hort. Sci. 117:745-748.

Sparks, D. 1993. Chilling and heating model for pecan budbreak. J. Amer. Soc. Hort Sci. 118:29-35.

Sparks, D. 2005. Adaptability of pecan as a species. HortScience 40:1175-1189.

One aspect of this I do not hit upon is tree response to day length (photoperiod). Although timing of budbreak is highly heritable, other factors can influence it, such as shorter photoperiods.  Pecan trees are great survivors in our highly variable climate because they are native to the region.  In some ways they are very conservative in the spring, with late budbreak, but dangerously reckless in the fall (with late fruit ripening).  It is an interesting crop to observe and work with.  Right now (at the end of March) they are just beginning to show some green whereas other native and non-native trees have long since broke bud.  I wonder if such late budbreak is in some way a contributing factor to alternate bearing.

Pecan tree in south MS, just beginning budbreak at the end of March

Pecan tree in south MS, just beginning budbreak at the end of March

Buds begin to show green on pecan tree  at the end of March in south MS

Buds begin to show green on pecan tree at the end of March in south MS

 

A Visit From Dr. Scott NeSmith, UGA Blueberry Breeder

Last week, Dr. Scott NeSmith, blueberry breeder from the University of Georgia, came to Poplarville for a visit.  We talked about the current state of the Mississippi blueberry industry (as well as what is happening in Georgia).  He stated that some early blooms may have got nipped some from cold events in the last few weeks there, but he was unsure how much loss to attribute to it.  He was really interested in the cultivars currently being grown in Mississippi, so we headed on over to visit Luis Monterde.  At his farm we saw most of the bushes in full bloom, with scads of pollinators buzzing from bush to bush.  Dr. NeSmith asked if he had any Georgia releases.  Luis said yes (Alapaha and Vernon) and showed them to us.  Luis was high on Alapaha but expressed some reservations on Vernon.  Dr. NeSmith said that in Georgia, high fertility was to the detriment of Vernon, which preferred low fertility management.  He also suggested that the new cultivars Titan and Krewer might be good options here in Mississippi.  As plants have been difficult to get, not much of it is planted here yet, so only time will tell on that.  He did say they would split in the rain (Titan more so than Krewer).  The issue of growing southern highbush blueberries also arose in our conversation.  Luis said he has mostly given up on them (although he had one row), as they were difficult to keep alive for very long.  One suggestion Dr. NeSmith had was to try Camellia and/or Suziblue.  He believes they are “tougher” plants and can stand up better than other cultivars that have been tried in the past.  Luis asked him what Georgia growers were doing with Premier, and Dr. NeSmith responded “pulling it out” due to the unreliable yields.  After about 1.5 hours, we bid Luis goodbye and I took Dr. NeSmith back to Wiggins where he was staying.  He doesn’t make it over here very often, so it was good to be able to spend some time with him and pick his brain about new potential cultivars for Mississippi.

Luis Monterde (left) and Dr. Scott NeSmith (right)

Luis Monterde (left) and Dr. Scott NeSmith (right)