Archive for the ‘other diseases’ Category

Looking for samples of Exobasidium on leaves and fruit

Friday, August 15th, 2014

I am looking for some samples of a fungus that attacks leaves and fruit and produces round, white to pale green spots on the leaves and fruit.  When the leaf spots get old they can turn red, but will have white areas under the leaf.  This fungus will also produce white spots on fruit.   This fungus does not seem to be a large problem in Maine.  I am interested in collecting samples for a colleague who is trying to clearly identify this fungus so we will have a better idea of how to control it.

If you see this fungus in your field, please let me know. Thank you, Seanna Annis 207-581-2621 or

Round white spots caused by Exobasidium on leaves of rabbit eye blueberries, spots on wild blueberry leaves will be about 1/4 to 1/2" across

Round white spots caused by Exobasidium on leaves of rabbit eye blueberries, spots on wild blueberry leaves will be about 1/4 to 1/2″ across

Exobasidium on wild blueberry fruit

Exobasidium on wild blueberry fruit

Some reports of Botrytis blossom blight and Frost – June 6

Friday, June 6th, 2014

Botrytis with short hairsThere have been some reports of localized patchy frost damage the last week of May followed by Botrytis symptoms showing up this week.  Frost will make blossoms more susceptible to Botrytis infection.  I have heard this from growers in the Union area and around the Orland area.   In one field, we saw low levels of both frost and Botrytis infection on the blossoms.   One of the differences to previous years was the very short hairs of the Botrytis sticking out of the base of infected blossoms.  A hand lens will be needed to see this kind of Botrytis infection.   Please look at previous reports to see pictures of these different diseases. 

The rain over the last 2 days, Wednesday June 4 to Friday June 6th produced moderate to high risk of Botrytis infection across monitored blueberry areas.   Many growers are nearing the end of bloom, so there is little risk of further Botrytis infection that will impact the crop.  

Frost and Botrytis risk in some areas May 29th

Thursday, May 29th, 2014


In Northern Hancock at our Silsby Plains site and at our Deblois and Cherryfield weather station locations in Washington county, there were frost conditions overnight from Wed. May 28th to Thurs. May 29th.  Lee Beers is a PhD student studying cold tolerance in blueberries and his research has found conditions from 28 F to 24 F will cause some minor damage to flowers but temperatures below 24F will kill many flowers.  Temperatures at Cherryfield dipped to at least 26 F and at Deblois and Silsby Plains to dipped to 22 F for a number of hours.    All of the other weather station locations had temperatures above 30 F overnight.

Botrytis Risk

Two weather station locations, Dresden Mills and West Rockport reported weather conditions that produce a high risk of Botrytis infections, IF the fungus is present in a field.   This does not mean fields will get Botrytis, just that there is a risk of infection if the fungus is present.

Fields with mummy berry disease will also have killed blossoms, so please look at the symptoms to determine what has killed your blossoms.  Please take a look at previous blog posts or emails  for pictures and descriptions of the symptoms for Mummy berry blight, Botrytis blossom blight, and frost.

  Any questions please call Seanna Annis  1-800-897-0757 (Maine only), or email at

Mon. May 26 – Mummy berry blight and Botrytis blossom blight

Monday, May 26th, 2014

I think the mummy berry infection season is now over for 2014.  Any remaining cups would have dried up over the last few days, so there won’t be any spores to infect the plants.   I don’t think the wet weather we had this weekend or will have on Tuesday will be causing any infection periods for the mummy berry fungus.

You may be 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.


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.

Picture of mummy berry disease symptoms on leaves and flowers. gray powder is found at the base of dead flowers and leaves


Frost has been minimal this year but may occur in hollows or some more sensitive 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.


Picture of frost damage of blossoms, all flowers on a stem tend to be affected. On leaves, the youngest leaf in the center of the cluster have been killed. 

Botrytis blossom blight

You may see Botrytis blossom blight occurring in your field if you had some bloom last week.  The weather over this weekend only produced conditions for Botrytis infection at our North Ellsworth and East Machias/Whiting weather station locations.  Fields in these area are at risk of Botrytis infection, IF the fungus is in these fields.  You can scout for this disease in early blooming clones or dying tissue on weeds in the field.   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.  

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.

You will want to minimize any exposure of honey bees, bumble bees AND native pollinators to pesticides, including fungicides, during bloom.  Bumble bees and native pollinators will still be working pollinating your fields when poor conditions keep the honey bees in their hives.   The fungicides recommended for control of Botrytis blossom blight are considered non-toxic to honey bees BUT we do NOT know how native pollinators would react to these materials or how there may be subtle effects on honey bees and bumble bees. 

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. 

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

Picture of Botrytis blossom blight showing black hairs coming off of dead flowers or leaves

 Any questions please call Seanna Annis  1-800-897-0757 (Maine only), or email at

Thursday, May 22 Mummy berry disease and Botrytis blossom blight

Thursday, May 22nd, 2014

Hancock and Washington counties

Mummy Berry Disease

There was another infection period overnight for mummy berry disease at all fields with weather stations in Hancock and Washington counties.  Most cups will be dying off by now, but if you have a later or wetter field there is a chance you may have had infection period overnight.  Fungicide applications should protect your plants for about 7 to 10 days after application.   You have until about 3 days from the start of the latest infection to treat your plants to protect them. 

Botrytis Blossom blight
There were also conditions for a moderate to high risk of Botrytis infection around the weather stations at Sedgewick, North Ellsworth and Eastbrook/Waltham over  Tuesday, May 20th  and Wednesday, May 21st nights.   This does NOT mean these fields will get Botrytis blossom blight.  
 I suggest scouting for Botrytis blossom blight in early blooming clones  and dead weeds in those areas to look for the symptoms of the disease.  IF you find the symptoms, then your field may be at risk for Botrytis infection. 


Locations Mummy berry Infection  period starting Wednesday May 22nd 
Sedgewick 9:20am
North Ellsworth 11am
Eastbrook/Waltham 6:40pm
Deblois 9pm
Cherryfield 8:40pm
Jonesboro 8:15pm
Wesley  8:40pm
East Machias/Whiting 8pm

Any questions please call Seanna Annis  1-800-897-0757 (Maine only), or email at

Mummy Berry Infection and Botrytis blossom blight Wed. May 21

Wednesday, May 21st, 2014

Knox, Lincoln and Waldo counties

Botrytis blossom blight

This is the time of year to scout for Botrytis blossom blight on early blooming blueberry clones.  Look at dead open flowers, and any dead or dying tissue (leaves or flowers) you see on weeds near or in your fields.  The symptoms are dead, open, flowers with black hairs sticking out of them. You will probably need a magnifying glass or hand lens to see the hairs. Your flowers may also be killed by mummy berry disease, which will not have the black hairs sticking out of the dead tissue.    If you do have Botrytis in your field and are getting a lot of bloom, this wet weather over the next week may cause infections by this fungus.  It is only worthwhile to apply fungicides for Botrytis blossom blight if you are sure you have this disease in your field.  If you do not have this fungus in your field, no matter how much wet weather you get during bloom you will not get Botrytis disease.  Be careful to protect pollinators if you do have to spray for this disease, spray when pollinators are not in the field.

Mummy Berry Disease

Hancock and Washington counties

There were mature spore producing cups found in a few plots around the barrens on Tuesday.  Most locations the cups were drying up. I expect there are still a few cups around in the barrens and they will be finishing up this week.  If you have a later or wetter field there is a chance you may have had infection periods in the past few days. Infection periods occurred overnight on Mon. May 19th  and Tues. May 20th (please see chart below). Wet weather is expected to continue the end of this week.

Infection periods and fungicide applications

Your fungicide application should protect your plants for about 7 to 10 days.  With heavy rainfall, there may be a bit shorter protection than 10 days.   With the infection periods in the last 2 days, you have until about 3 days from the start of the infection to treat your plants to protect them.

If you would be applying a second application of propiconazole, it would be a good idea to switch to a different fungicide with a different mode of action to help prevent resistance to propiconazole developing in your field (Please see the 2014 fungicide chart).   Other fungicides should be applied as protectants and before infection periods occur.


Locations Infection  period starting Monday May 19th  Infection period starting Tuesday, May 20th
Dresden Mills likely none likely none
West Rockport likely none likely none
Appleton likely none likely none
Belfast  likely none likely none
Sedgewick 10am 3:40pm
North Ellsworth continued from Sun. May 18th 1:40pm
Eastbrook/Waltham 5:40pm 6:20pm
Deblois station down station down
Cherryfield 4:40pm 4pm
Jonesboro 3:45pm 7:45pm
Wesley  2:40pm 6:40pm
East Machias/Whiting 4pm 6pm

Valdensinia leaf spot

Tuesday, July 16th, 2013

Now is the time to look for Valdensinia leaf spot in your fields.  The wet weather conditions we have had over the last month will have caused many cycles of spore production and infection if you have this fungus in your field.  I have seen a new field with Valdensinia leaf spot in Ellsworth.  Areas we have often found it are along the edges of roads, in wet areas in the field and areas that are shaded by trees along the field edges.

Do NOT scout your field when the plants or ground is wet.  This may move infected leaves  around your field. 

Symptoms are large brown leaf spots that are rounded with dark margins compared to the inside of the lesion.  On the underside of the lesion, you will see a dark spot with a hand lens, or sometimes the naked eye, which is the spore still attached to the leaf.  Lower leaves, particularly in prune fields, will be falling off by now.  Upper leaves, particularly in crop fields, may have many spots and may still be attached. 

If you think you have Valdensinia leaf spot, please contact Seanna Annis at or the blueberry hotline 800-897-0757 (in Maine only).

lowbush blueberry stems with missing leaves and leaves showing Valdensinia leaf spot symptoms     Picture of leaves with Valdensinia leaf spot lesions


Botrytis blossom blight

Wednesday, May 22nd, 2013

If you have had Botrytis blossom blight in your field before, you may have conditions to have this disease occur this week.    The Botrytis blossom blight can be identified by the black hairs that stick out of infected, dead blossoms.  Blossoms can also be killed by the Mummy berry fungus and frost.  Please see previous post from Monday May 20th for pictures of symptoms of these diseases.

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.

Weather station location Chance of Botrytis Blossom Blight infection
West Rockport High
Appleton High
Sedgewick High
Ellsworth low
Silsby Plains low
Deblois moderate
Montegail  moderate
Rocky Pond low
East Machias low
Meddybemps low

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