My recommendation is NOT to apply fungicides to control Botrytis blossom blight unless you are SURE you have it in your field.  In my experience  visiting many fields reported to have Botrytis blossom blight is that the dead blossoms have been due to Mummy berry disease in the majority of fields. 

ONLY apply fungicides to control Botrytis blight IF 1) you have seen severe infection this year in early clones, this means more than one or two blossoms affected, and 2) you have had a severe problem with Botrytis blossom blight in previous years.

If you do apply fungicides during bloom, apply them at LATE EVENING or at NIGHT to minimize the exposure of pollinators to these compounds.

I would only suggest applying fungicides for Botrytis blossom blight control, if you are sure that is what has killed off your blossoms in the past or you have already seen this disease in your crop field this year. Please follow the recommendations on the Factsheet # 219 Disease Control Guide for Wild Blueberries for 2013. 

As of 11am on Wed. May 22 there were some monitored fields that had high probability of Botrytis infection of blossoms this past week.  With the weather forecast predicting rain through out the state until Sunday, I expect more possible blossom infection from Botrytis.

If you have any questions please contact Seanna Annis via email at sannis@maine.edu or by phone 107-581-2621.

The goal with this post is to relate some information about these genera so farmers and growers can know more about the bees found in their fields.

Andrena: All species of this genus nest in the ground. They dig tunnels and excavate small cells off the main passageway where they place a smooth ball of pollen and lay an egg. The pollen becomes the food for the larvae that hatches from the egg. The pollen comes from the flowers the female bee visits in the blueberry fields. Usually the female have their own individual nests, but sometimes they are clustered in the blueberry fields in fairly dense aggregations. You most easily find the nests in the early spring when the blueberry leaves are not fully out. Just look for a black and yellow/white bee- smaller than a bumblebee- landing on or taking off from the ground. About 28% of the bees I’ve caught are Andrena and they have been in all fields. I’ve been able to look at the pollen the adult females are carrying when I catch them and have found the pollen loads to average about 78% blueberry pollen which means that most of these bees visit blueberry plants very frequently. I would categorize Andrena as important wild pollinators.

When the blueberry flowers start to fade I’ve found these bees foraging on raspberry, blackberry, rose, and sheep laurel (lamb kill).

There is more information about this genus in an entry posted Oct. 25, 2012.

Halictinae bees: These can be bright green, so when you see metallic flashes as a bee flies by you are most likely seeing one of this group. Some are black with white bands on the abdomen. They often are small- just about 6-12 millimeters long. They mostly make nests in the ground. They either nest on their own, or communally, or even make different classes of workers like a honeybee or bumblebee. A little over 60% of the bees I’ve caught are from this group- the vast majority from the genus Lasioglossum. They are found in all fields. Some species from this group are probably important pollinators for blueberry (the few Halictus I’ve been able to examine have 100% blueberry pollen in their pollen loads). But, I’m unclear how much pollination can be attributed to Lasioglossum or Augochlorella. 

 This photo is of a Halictinae bee, Agapostemon virescens, emerging from a nest.  At this site, located on Blue Hill Mountain, multiple females used the same two nesting holes.  Photo from July 1, 2012. 

 Cleptoparasitic bees: I’ve commonly caught two genera that fall into this group: Nomada and Sphecodes. These bees don’t make their own nests and don’t gather their own pollen. Instead they enter the nests of other bee species, destroy the egg that has been laid there and lay their own egg so their young can feed on the pollen. I’ve caught these bees while they visit blueberry flowers (most likely consuming nectar), but since they don’t gather pollen they can’t be considered significant pollinators of blueberry.

From Sara Bushmann, sara_bushmann@umit.maine.edu

You may start seeing symptoms of Mummy berry disease in your field  now and over the next week.    It is too late to spray fungicide at this time. Any symptoms you find are from infections that occurred at least 9 to 10 days ago.  The spores produced on the dead leaves and flowers will NOT cause new killing infections. These spores will infect healthy flowers and produce mummy berries. The number of mummy berries produced are typically too low to be concerned about trying to control this stage of the disease.

MUMMY BERRY SYMPTOMS

Symptoms of mummy berry disease are shown in the pictures below. This fungus does attack and kill both flowers and leaves.  Flowers are typically killed before they open.  The petiole (base of leaf) of leaves give a characteristic shepherd’s crook shape.  Powdery gray spores can be seen at the base of the leaves or flowers where they attach to the plant. Unless it is a very susceptible clone, you will only see isolated leaves and flowers with the disease.

FROST

You may also see frost damage in some clones. Frost tends to affect most of the flowers on a stem. You may also see just the green growing tip of the leaf dying off. Please see pictures below.

Botrytis blossom blight

If you have had Botrytis blossom blight in your field previously, this is the time of year to scout for it in early blooming clones.  The symptoms are dead, open, flowers with black hairs sticking out of them (see picture below). You will probably need a magnifying glass or hand lens to see the hairs.   If you do have it in your field, this wet weather over this week may cause infection by this fungus.  It is only worthwhile to apply fungicides for Botrytis blossom blight if you are sure you have had this disease in the past and it has affected your yield.

If you have any questions, please email Seanna Annis at sannis@maine.edu or call 207-581-2621.

Mummy berry cups dried up early this week so it is unlikely there were any infections in your area in this last rain.

Northern Hancock and Washington counties

Most cups are finished from our monitored field sites.  Only one mature cup was still reported at Long Pond area near Deblois  today.  All the rest of the monitored sites, around Deblois, Wesley, Cherryfield and along the coast to East Machias do not have any remaining cups.  I expect the cups to be finished completely within a couple of days.

If you have a late field, there is a chance you may still have cups in your field and may have had an infection period last night.

For those of you who might have had an infection period last night, if you have applied fungicide on or after Monday May 6th, your plants were protected during this last infection period last night.  I would only recommend fungicides if you have a late field that is not yet elongating flower buds and has a history of severe mummy berry disease.  If you have not applied fungicides, you have until Sunday  May 19th  in the evening  to apply fungicides to kill any infection.    You will want to consider if you have bees in your field in your decision to apply fungicides.

If you have any questions please contact Seanna Annis via email sannis@maine.edu or by phone 207-581-2621.

The following table shows when the frost occurred in our monitored fields so fields in the surrounding areas may have experienced frost damage.

The weather forecast is for warmer night temperatures for the rest of the week.  Any questions please send me an email sannis@maine.edu or call 207-581-2621. Seanna Annis

Our Meddybemps weather station  indicated there was an infection period in that field last night starting at 7:20pm and continuing to  8:40am.    For this infection period in the Meddybemps area if you have applied fungicide on or after Sunday May 4th, your plants were protected during the infection period overnight.  If you have not applied fungicides, you have until Thursday May 16th  in the evening  to apply fungicides to kill any infection.    You will want to consider if you have bees in your field in your decision to apply fungicides.

Other areas

No infection periods were indicated in our other monitored fields.

The temperature dipped below 30F at our Silsby Plain field, but no where else.  In Silsby Plain, it was below 30F from midnight to 1:20pm. This may cause frost damage to fully open flowers.

Any questions, please contact Seanna Annis at 581-2621 or send me an email sannis@maine.edu.

The mummy berry cups were finishing up last week and unless you had a very late field, you probably did not have any infection over this past weekend.

Waldo and Southern Hancock counties

The mummy berry cups were finishing up a the end of last week, but there may have been infection periods over this weekend in your areas.  If you have a mummy berry plot, I would like to know if it is finished or not. 

Northern Hancock and Washington counties

There were infection periods in fields in these areas over the weekend.

Mature mummy berry cups were reported across this area on Friday, but no new cups or pinheads were observed.   I expect these cups will be finished by early this week. 
If you have a mummy berry plot, I would like to know whether the cups are finished.  

Frost warning

Temperatures dipped drastically on Sunday night and are expected to be in the 30sF for the next two nights. From Lee Beers graduate work, fully open flowers can be damaged at temperatures below 30F.

For these last infection periods starting on Saturday, if you have applied fungicide on or after Thursday May 2nd, your plants were protected during the infection period this past weekend.  If you have not applied fungicides, you have until Wednesday May 15th  in the evening (depending upon the field) to apply fungicides to kill any infection.    You will want to consider if you have bees in your field in your decision to apply fungicides.

Any questions, please contact Seanna Annis at 581-2621 or send me an email sannis@maine.edu.

The good news for more southern fields in Knox and Lincoln counties is that  I suspect the mummy berry cups are finished or just about.  Unfortunately, I do not have a grower monitoring a mummy berry plot that far south so this is my best estimate  considering the reports from other areas.  If you have a late field around West Rockport area you may have experienced an infection period.

The rest of the monitored fields still have reports of mature cups so they do have the fungus around and are likely to have had another infection period overnight.   I expect we are near the end of the season and the warm dry weather next week will finish off the cups.

Remember your plants are susceptible even if the leaves are unfurled and flowers are starting to appear.    

For this last infection period, if you have applied fungicide on or after Wednesday May 1st, your plants were protected during the infection period last night.  If you have not applied fungicides, you have until Monday May 13th  in the evening (depending upon the field) to apply fungicides to kill any infection.

I would like to hear from anyone with a mummy berry plot, to know if their mummies are still producing cups or finished. Please call 207-581-2621 or send me an email at sannis@maine.edu.

If you have any questions, please contact Seanna Annis at sannis@maine.edu, or 581-2621.

Remember your plants are susceptible even if the leaves are unfurled and flowers are starting to appear.   Mature mummy berry cups are dying off but there are probably some mature cups still present particularly Downeast.    I expect we are at the end of the season, but the rain predicted to occur through out Maine on Saturday will produce another infection period. 

I would like to hear from anyone with a mummy berry plot, to know if their mummies are still producing cups or finished.  Please call 207-581-2621 or send me an email at sannis@maine.edu.

For this last infection period, if you have applied fungicide on or after Tuesday April 30th, your plants were protected during the infection period last night.  If you have not applied fungicides, you have until Sunday May 12th  at 4 to 9pm (depending upon the field) to apply fungicides to kill any infection.

Any questions, please contact Seanna Annis at sannis@maine.edu, or 581-2621.