Last week, we held a workshop in Mt. Vernon, Washington for blueberry growers. The topics included mulching for mummy berry control options, environmental factors influencing apothecia production, spray options for control, spotted wing drosophila, and other pathogens of concern.
Dalphy discusses environmental factors influencing apothecium production.
Jay discusses spray options for controlling mummy berry.
Participants view spotted wing drosophila demo.
Jade discussed experimental results showing that 2 inches of Douglas Fir sawdust maintained until March significantly reduced apothecia emergence in comparison to bare soil and leaf cover.
Table: Most common commercial blueberry cultivars grown in the PNW (according to Strik’s Blueberry Production in the Pacific Northwest) and ranked from most resistant to mummy berry to most susceptible according to research (MK Ehlenfeldt, 2010).
Remember that cultivars not recommended for commercial production (many of which are highly susceptible to mummy berry like Berkeley and Bluetta) are not included.
Check out the cultivar publication below!
We discussed the benefits of harvesting mummies.
Responses from Surveys:
Most growers had some presence of mummy berry in the field. With most participants falling into the 1-15% range.
Overall, mummy berry levels were “about the same” in comparison to last year.
Most growers report that they are currently mulching for disease control.
Most growers mulch 1-2 inches.
Most growers are mulching from January-April. Let’s move those March-April mulches to February! You risk apothecia sporulation by waiting until March-April!
Of course, Douglas Fir Sawdust is a favorite among mulch options.
Answers to Mummy Berry Questions:
Mummy berry infected fruit
Should leaves be removed and do they interact with apothecia?
From data collected in 2014 (unpublished), there was a slight association with leaves and fewer apothecia as compared to bare soil.
What happens if apothecia are produced prior to bud break?
According to our current biological understanding, nothing. We must have a susceptible host (at bud break), a virulent pathogen (M. vaccinii-corymbosi), and a conducive environment (favoring spore production).
Can a mummy last >1 season?
We’re currently looking into that question. Stay tuned for updates!
When do apothecia first appear in the PNW?
Between the months of March and April.
What’s up with this talk of beginning activity in November-February?
That’s when we begin to see germination. See picture below.
A germinated mummy. With the right environmental conditions, it will produce an apothecium (fungal fruiting body, like a mushroom).
Have you heard about using maple or oak leaf mulches?
I haven’t, but that’s something we could look into in future experiments.
What about using weed mats?
We’re first answering the question of whether mulching consistently works in suppressing apothecium formation. Later questions may include the use of weed mats. From my observations at a grower’s operation that had weed mats, mummies appear to fall between the cracks and germinate underneath.
Why did you look at leaf mulches?
I was looking at the potential benefit of removing leaves, which is why my experiment had both a leaf treatment and a bare soil treatment. I wasn’t looking at leaf mulches in particular.
Is weed management important for execution of this cultural control method?
We haven’t formally tested this, but from my observations, it is important. I went to a grower’s field that was lacking weed control and mulching on top of the grass was messy and uneven. It was difficult to tell whether we had fully covered the ground and with the winter rains, the mulch was likely to shift around.
What do apothecia look like?
Here’s a picture! See below.
Apothecia arising from stipes
What about mummies that roll into the alleys?
For this reason, many growers choose to rake their aisles during the fall-winter months and dispose of debris. One grower reported to me that he found this practice to be effective.
Do apothecia arise from stipe initials?
Yes! First they germinate.
Germinated mummy during winter
Then, when conditions are favorable, apothecia will arise from these initials.
What happens if they’re disturbed?
We haven’t studied this in particular, but from my observations, it’s not very detrimental. I often bring collected mummies from the field into the lab and get them to produce apothecia. That’s a fair amount of disturbance.
What temperature is too hot for germination?
60F has been shown to be a temperature not conducive to apothecia development in experimental trials (Wharton and Schilder 2005).
What about day length? Are mummies sensing that?
We think so! But no conclusive evidence yet.
If you use a burner (hot water or propane burner), can you eliminate spores?
No experimental evidence of this yet, but anecdotal reports from farmers, say yes.