Is Mummy Berry Starting Already?

I received the information below from University of Georgia Plant Pathologist Dr. Phil Brannen. It states that in Georgia, mummy berry infection is likely right now due to the warmer weather conditions.  We have also had these conditions in Mississippi, so it would be a good idea to keep mummy berry control in mind, especially for southern highbush blueberries.  Meanwhile, rabbiteyes are not far behind.

Dr. Harald Scherm ran the mummy berry model today, and it indicates that we are currently in a DANGER period for mummy berry disease initiation.  Harald stated that the temperature-driven model indicated that apothecium (spore-forming structure that develops from overwintered mummies on the ground and in debris) emergence should be well underway based on the balance of chill-hours and degree-days received. In fact, there could be a chance that the apothecia ejected spores earlier than normal, possibly allowing for infection of early-blooming southern highbush varieties. This assumes that soil moisture conditions have been favorable, which they likely have been.  Rabbiteyes will soon be showing green tip or early bloom, which should initiate the spray program for mummy berry management.  For additional information on fungicides which are available for management of mummy berry, refer to the blueberry IPM guide at www.smallfruits.org. “

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Some Tidbits Learned from the Southern Blueberry and Fruit Workers Meeting

Recently I attended the Southern Blueberry and Fruit Workers meeting in Atlanta, GA.  It is held as part of the Southern Region of the American Society for Horticultural Science annual conference.  Below are some new things I learned about at the meeting:

Ring nematode is prevalent in Georgia blueberry plantings

The nematode problem is worse in re-plant situations and may require fumigation

Southern highbush blueberries have more problems than Rabbiteyes, especially in re-plant situations

Using pine bark mulch appears to reduce nematode populations

The addition of humic acid to the soil does not appear to benefit blueberry plants

Botrytis resistance to fungicides has happened in GA.  Use of Captan or Ziram is now recommended because of low resistance possibility

Mummy berry sprays should be applied starting at first sign of green tissue.  Indar, Orbit, Pristine, and Proline (a new material) showed efficacy.  Serenade, an organic product, also had some efficacy.  Regalia, another organic product, had no effective control of the disease.

Exobasidium is becoming resistant to Pristine in GA.  ‘Premier’ has high infection rates, as does Tifblue.  A full Captan spray schedule is effective (about 8 sprays in GA), but not using Captan as a delayed dormant spray.  Use Lime Sulfur or Sulforix for best control as a delayed dormant spray.

Xyllela (blueberry scorch) has been found in various states.  In Rabbiteye’s  it leads to chronic symptoms, but in Southern Highbush scorch symptoms are readily apparent.  There may be different strains of this disease and more work is being done.

Blueberry Necrotic Ring Blotch is a non-systemic viral disease that is only in leaves.  Mites spread it.  It can lead to defoliation of the plant.

Broad mites have been found in blueberries and blackberries in Arkansas.  Damage resembles Roundup injury.  Leaves have a “silvery” look, with rosetting and stunting of plants, and necrosis of the petiole.  It will kill shoot tips.

Blueberry rust is a problem in Gulf Coast areas of Alabama.

Foliar calcium spray trials in GA on rabbiteyes have shown no efficacy

Three new Southern Highbush blueberries are being released from UGA soon.

One new Rabbiteye cultivars is also being released from UGA – Krewer, an early, large fruited cultivar that should pair well with Titan

Blueberries and Chilling Hours

One of the last things one might consider when choosing a blueberry cultivar is chilling requirement.  A chill hour can vary depending on the model used, but the most common model in this region defines it as the number of hours below 45 F.  This is a requirement for the plant to satisfy its dormancy and thus to grow and fruit normally the following year.  In regions where cold temperatures are more common, plants can remain in a quiescent phase even after their chilling hour requirement has been met.  However, in warmer climates this may not be the case, so early flowering is a problem in low-chill cultivars.  Today, I have an example of that with a Florida-based, Southern Highbush cultivar, Springhigh.  As defined by the Florida Foundation Seed Producers, Inc., “‘Springhigh’ is a very vigorous, upright bush with excellent survival in the field.  It ripens about 9 days earlier than Star.  Berries are very large and medium dark, with good scar and flavor and medium firmness.  Sets fruit well even when pollination conditions are poor.”

Springhigh blueberry

Springhigh blueberry

‘Springhigh’ is reported to have a chilling requirement of around 200 hours, which is considered to be low-chill.  Today is December 18, 2012 and the place is Poplarville, MS.  We have gotten past the 200 chill hour mark for this year, although we have not gotten very cold at all (barely below 32F).  Let’s take a look at the state of  ‘Spring High’ in mid-December.

Buds are popping in mid-December.

Buds are popping in mid-December.

Flowers are showing in mid-December.

Flowers are showing in mid-December.

Fruit set in mid-December.

Fruit set in mid-December.

Large, developed fruit in mid-December.

Large, developed fruit in mid-December.

I was surprised at how much fruit this plant had on it.  As you can see it has all stages of reproductive growth on it right now.  Now, it is not all over the plant, many buds have not pushed yet, but if the weather continues as it has….who knows?  If we get a hard freeze then the fruit would certainly be a loss, but in the absence of that the productivity could be poor because no one is prepared to harvest plants so early in the season.  There is a reason we don’t really recommend very low chill types here.  Even along the coast they could get zapped.

So, chilling requirement is an important consideration in your growing region.  There are many cultivars out there that “fit”, so finding one is not a problem — it is knowing the chilling requirement before planting and pairing the cultivar with the site that is important.