Polyculture or Monoculture?

Image by DragonGuRo. Polyculture cactus vs. monoculture carrot!

Image by DragonGuRo. Polyculture cactus vs. monoculture carrot!

I had a great time presenting my research at the Oregon Mycological Society meeting on Monday. Following my presentation, I reoms_logoceived lots of questions and the next day I was still receiving questions via email. I felt that one question in particular would be of interest to anyone reading this blog, so I decided to turn it into a post! I’ve been wrestling with exactly how to answer this question, as there are many facets to it, so I attempted to answer it in a broad sense, touching on some of the major points that I’ve read about in the literature. At the bottom, I’ve included a few selected references, so that you can read up on this too and begin forming your own opinions!


What affects the susceptibility of plants within an agricultural population, as opposed to a natural population?

There is a widely-accepted theory that an association exists between disease epidemics and monocultures (defined by the American Phytopathological Society as “the growth of the same plant species in close proximity, with few or no other types of plant present”), as compared to polycultures (multiple crops in the same space, in imitation of the diversity of natural ecosystems).

This theory, while it has some exceptions, arose from observations of the agricultural landscape.

There are 2 major factors that are thought to play a role in the differences seen in disease severity between monocultures and polycultures:

  1. Genetic diversity of the population
  2. Host population size

Let’s examine them one at a time.

#1: Genetic diversity of the population

Plant pathogens can come in many forms– fungi, nematodes, bacteria, viruses. In order for a plant pathogen to cause disease, we need 3 ingredients:

Image by Jade Florence. Disease Triangle.

Image by Jade Florence. Disease Triangle.

  1. Virulent Pathogen
  2. Susceptible Host
  3. Conducive Environment

Within the field of plant pathology, these 3 ingredients are visually displayed as the “disease triangle”.

The idea behind increasing genetic diversity is that diversity decreases the likelihood of a single pathogen genotype inciting disease on most or all plants. The more diversity, the higher the likelihood that the crop as a group has a broad range of genetic resistance to combat the single pathogen genotype. (This is greatly simplified, but communicates the general idea).

Of course, this is operating under the assumption that there is only one pathogen genotype in a given field. This assumption is often broken, however. Read King 2012 for more information (cited below).

In natural ecosystems, on the other hand, we frequently see a good deal of genetic diversity in stands of flowering plants that are not suffering from recent ecological disturbance.

#2:  Host Population Size

The idea behind host population size largely relates to inoculum load (or for fungi, amount of infectious material produced such as spores). By having susceptible cultivars grouped together in a field, a pathogen that is able to infect one cultivar can reproduce and will have a relatively short distance to travel to reach the next susceptible host. For this reason, it is often recommended that growers use cultivar mixtures.

In many natural systems, we see plant species dotting the landscape– some Ribes sanguineum over here, some Aquilegia formosa over there. Each utilizing whatever space is available that can provide it with the precise conditions it needs to survive. This natural spacing of plants that occurs due to the utilization of limited resources, can create a barrier (of unoccupied space, or of other plants) that protects the individual plant from the inoculum coming from diseased neighboring plants.

Are polycultures always better?

Image by Jade Florence. Many natural ecosystems are biodiverse.

Image by Jade Florence. Many natural ecosystems are biodiverse.

The short answer is no. While many natural ecosystems are biodiverse, there are some that are not. For example, wild relatives of wheat often form dense stands that are comparable to the density found in cultivated fields. For more information, read Wood 1998, cited below.

Image by Rocketclips, Inc. Wild wheat blowing in the breeze.

Image by Rocketclips, Inc. Wild wheat blowing in the breeze.

Furthermore, functional diversity must be taken into account. Not all blends of plants will inherently lead to decreased disease pressure.

For example, a farmer is trying to avoid mummy berry disease and decides to increase diversity. She plants 5 different cultivars of blueberry, but they all happen to be susceptible! She may see an increase in disease.

The same can hold true even if you define diversity as meaning different crop types, as opposed to simply different cultivars.

For example, a farmer has a problem with the fungal pathogen, Sclerotinia sclerotiorum, which has a very wide host range including legumes, sunflowers, vegetables, and stone fruits. He makes the mistake of planting snap peas, tomatoes, and peppers in close proximity to each other. Again, this farmer may experience increased disease.

This is the basis of the idea of functional diversity. The plants chosen for a mixture, and thus a polyculture, should be chosen mindfully with the pathogen populations that you want to avoid in mind.

A good start is to consider where you live, the crops you’re growing, and the potential pathogens you might encounter. Resources such as the Pacific Northwest Disease Management Handbook can help you determine pathogens of concern, so you can take steps to begin adding diversity to your garden/farm if you believe the ecosystem would benefit from increased diversity.

Taking cues from nature and applying this knowledge to your home garden/farm is a great step towards maintaining a healthy agroecosystem, but just remember, not all ecosystems are equally diverse. A sun-soaked savannah may have a vastly different amount of diversity than a tropical rainforest, yet both ecosystems can be stable, productive, and resilient to disease epidemics.

And finally, a note about the complexity of nature. It’s very difficult to simply say A+B always equals C. But luckily, we have researchers and extension programs that are constantly at work trying to figure out how to produce more food in a more sustainable way. So, be sure to stay abreast of the latest research and while your at it, conduct your own! Your particular environment will have distinctive needs and it’s important to take these needs into account when making changes to your production system.

Selected References

King, K. C., and C.M. Lively. 2012. Does genetic diversity limit disease spread in natural host populations? Heredity 109: 199-203.

Mundt, C. C. 2002. Use of multiline cultivars and cultivar mixtures for disease management. Annual review of phytopathology 40: 381-410.

Wood D. 1998. Ecological principles in agricultural policy: but which principles? Food Policy 23(5): 371-381.

Posted in Cultivar Susceptibility, Resources, Uncategorized | 1 Comment

Oregon Mycological Society Talk to be Held in Portland

Image by Jade Florence. Mummy berry disease on blueberry, caused by Monilinia vaccinii-corymbosi.

Image by Jade Florence. Mummy berry disease on blueberry, caused by Monilinia vaccinii-corymbosi.

If you’d like to learn more about the biology and life history of fungi, I will be presenting a talk about Monilinia vaccinii-corymbosi, causal agent of mummy berry disease, at the upcoming Oregon Mycological Society meeting this Monday, June 22 in Portland, OR. Details below.

Date: Monday, June 22

Location – World Forestry Center, 4033 SW Canyon Rd, Portland, OR 97221.

Image by Jade Florence. Apothecia of Monilinia vaccinii-corymbosi.

Image by Jade Florence. Apothecia (or mushrooms) of Monilinia vaccinii-corymbosi.

Exit 72 from US 26

Doors open at 6:30 with an informal identification table

Meeting begins at 7:30 with a short business session

My presentation will begin at approximately 7:45

I plan to speak for ~ 50 minutes, with some time for  questions afterward.

Other updates:

An extension publication about mummy berry management in the Pacific Northwest is due July 8, 2015. I’ll post a link to the publication when it is available.

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Bye-bye apothecia!

I have surveyed two farms in the Willamette Valley and we are seeing NO MORE APOTHECIA. Yay!

Image by Jade Florence. Bluettas in Bloom

Image by Jade Florence. Bluettas in Bloom

I recently received a related inquiry regarding apothecia presence and the Visqueen-Mulch system. I answer the question below.


Here’s the question:

Thanks so much for your blog and analysis.

We are using the plastic this year to see how this limits mummy berry in the coming season.  One thing we are wondering, is there any damage done to the plant ecosystem, roots, etc. by having this plastic down.  We have buttoned it up snuggly around the plant crowns, and down into the aisles… We are wondering when we can start to remove this plastic.  We haven’t seen apothecia, but they could be present – they are pretty good at hiding.  When will the folks using plastic remove it?  We are slightly north of you, but our climate is quite similar to yours, I believe.

 Again thanks for your help.  We hope to get down to one of your workshops soon!


Response:

As far as I’ve seen around the Willamette Valley, there are no more apothecia.

However, based on Ken Berg’s system, you should pull back the Visqueen after all the blooms are gone/done, or the vast majority anyway – which is generally around the end of May. This will allow mummies to naturally drop at harvest, so they can be covered again the next February.

If you want to remove it sooner, there’s a scouting video in the Multimedia tab up top^^. You can try to see for yourself whether or not apothecia are still being produced on your farm.

I haven’t seen any particular research saying that damage is done to the soil ecosystem by having plastic down. Although, I have presented data on weed mat systems at our grower workshops, which may be transferable to Visqueen plastic.

Image by Jade Florence. Blueberries with Weed Mat

Image by Jade Florence. Blueberries with Weed Mat

If you choose to use weed mats as a year-round weed control strategy, there needs to be a drip irrigation system set up beneath the weed mat or plants may not get watered enough. You may want to consider this for the visqueen plastic also.

Additionally, it’s best to put some organic matter under your weed mat/visqueen plastic. However, if you’re following the Visqueen-Mulch system directions that I posted in February, you’ve already mulched under your plastic.


I hope everyone is having a good growing season. Happy April!

Posted in Farm Update, Farmer-to-Farmer Ideas, Integrated Pest Management | Leave a comment

4.13.15

Quick Update: Apothecia counts are low in Corvallis and Eugene, at the 2 sites I’ve checked. I’m expecting that we’ll be down to zero by next week. I’ll keep you updated when I check the fields this week.

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4.10.15

There are still apothecia developing at the Botany and Plant Pathology Field Lab in Corvallis, OR. This is a really long sporulation period!! Additionally, there are apothecia in Eugene. They were first sighted on March 20, 2015 and new ones are continuing to develop.

Image by Jade Florence. The stars on the above map represent areas with confirmed sporulation occurring during the 2015 bud break period.

Image by Jade Florence. The stars on the above map represent areas with confirmed sporulation occurring during the 2015 bud break period.

The sporulation period is winding down and I’m beginning my data analysis for experiments this year. I will post updates as I complete my analysis!

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3.12.15 Apothecia!

Apothecia have been found at the BPP Field Lab in Corvallis, OR.

Image by Jade Florence. Stars depict PNW towns where apothecia have been spotted this month- Orca's Island, WA and Corvallis, OR

Image by Jade Florence. Stars depict PNW towns where apothecia have been spotted this month- Orca’s Island, WA and Corvallis, OR

Image by Jade Florence. Apothecia have been found in the field.

Image by Jade Florence. Apothecia have been found in the field.

Have you found them where you live? Leave a comment in the space below!

We’re getting ready to collect data from our field trials. Make sure your blueberries are protected! The Bluettas are beginning to flower and the Berkeleys are trailing behind.

Image by Jade Florence. Bluettas in Bloom

Image by Jade Florence. Bluettas in Bloom

Image by Jade Florence. Berkeleys Trailing Behind

Image by Jade Florence. Berkeleys Trailing Behind

Cheers!

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3.1.15

Still no apothecia found in Corvallis, OR! But we’re getting very close!

And here’s a link to a table of blueberry growth stages! Click on the picture!

Screen Shot 2015-03-02 at 11.05.22 AM

Or Click here

 

Update: According to a comment left on the Mummy Berry Blog, Orca’s Island, WA has apothecia!

Image by Jade Florence. The star indicates the location of Orca's Island, where apothecia have been reported.

Image by Jade Florence. The star indicates the location of Orca’s Island, where apothecia have been reported.

Posted in Farm Update, Resources | 3 Comments

Update on Bud Break and Mummy Status

I just got back from the Botany and Plant Pathology Field Lab in Corvallis, Oregon. Here are some pictures of the blueberries.

Image by Jade Florence. Floral bud break on Bluetta blueberry bush

Image by Jade Florence. Tight cluster on Bluetta blueberry bush

Image by Jade Florence. Floral bud break on Bluetta blueberry bush

Image by Jade Florence. Early pink bud on Bluetta blueberry bush

Contrastingly, here is an image of bud swell occurring on Berkeley blueberry bushes.

Image by Jade Florence. Bud swell on Berkeley blueberry bushes.

Image by Jade Florence. Bud swell on Berkeley blueberry bushes.

Image by Jade Florence. Bud swell on Berkeley blueberry bushes.

Image by Jade Florence. Bud swell on Berkeley blueberry bushes.

And now for the mummies. Here is a sample of what I found today…

Image by Jade Florence. A germinated pseudosclerotium (mummy) with many stipe initials

Image by Jade Florence. A germinated pseudosclerotium (mummy) with many stipe initials

Image by Jade Florence. And another pseudosclerotium (mummy) that is primed and ready to produce apothecia (fungal fruiting bodies, much like mushrooms).

Image by Jade Florence. And another pseudosclerotium (mummy) that is primed and ready to produce apothecia (fungal fruiting bodies, much like mushrooms).

Image by Jade Florence. A pseudosclerotium (mummy) that is just about ready to produce an apothecium!

Image by Jade Florence. A pseudosclerotium (mummy) that is just about ready to produce an apothecium!

 

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Warm Weather This Early?! What’s the Threat of Mummy Berry Disease??

The warm weather has definitely taken many growers by surprise, with floral bud break on the Bluetta variety of blueberries already occurring. We’re getting many calls and emails asking:

“Are apothecia present yet? And should I be spraying?!”

Our field was checked on Monday of this week (2/23/15) and NO apothecia are present yet.

Image by Jade Florence. Mummies overwintering.

Image by Jade Florence. Mummies overwintering.

We’re still waiting on vegetative bud break, which is when apothecia develop. I’ll be checking the field again tomorrow (February 27, 2015) and will post pictures of bud break on both Bluettas and Berkeleys, along with more images of mummies in the field to give you an idea of what’s happening in Corvallis, Oregon.

In the meantime, if you want to know what stage your mummies are at, check out the Multimedia tab at the top of the page for a video about scouting for mummy berry in your fields!


 

Below is a list of the mummy berry stages you’re likely to see at this time of year

Stipe initial noun a hardened protrusion that grows from the pseudosclerotium (mummy) and serves as the foundation of the apothecium (mushroom or fungal fruiting body)

Mummies that are dormant in the field are less of a threat than those that have germinated. Mummies must have a stipe in order to produce an apothecium.

Image by Jade Florence. Pseudosclerotia that lack a stipe initial are less of a threat than those that have germinated. Mummies must have a stipe initial in order to produce an apothecium.

A pseudosclerotium that is at the "germination stage"

Image by Jade Florence. A pseudosclerotium that is at the “germination” stage. Stipe initials are up to 4.9mm long.

A pseudosclerotium at the "emergence" stage. This stage is characterized by stipe initials from 5mm up to 15mm typically.

Image by Jade Florence. A pseudosclerotium at the “emergence” stage. This stage follows “germination” and is characterized by stipe initials from 5mm up to 15mm typically.

Image by Jade Florence. Apothecia (fungal fruiting bodies) are produced coinciding with blueberry vegetative bud break.

Image by Jade Florence. Apothecia (fungal fruiting bodies) are produced coinciding with blueberry vegetative bud break.

As usual, if you have any questions or concerns, leave a comment below. Cheers!

Posted in Farm Update, Resources | Leave a comment

February 11 Workshop Recap

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.

photo-1

Dalphy discusses environmental factors influencing apothecium production.

photo-2

Jay discusses spray options for controlling mummy berry.

photo-3

Participants view spotted wing drosophila demo.

14FieldResultsSimple

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 (Ehlenfeldt). Remember that cultivars not recommended for commercial production (many of which are highly susceptible to mummy berry like Berkeley and Bluetta) are not included.

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!

Blueberry Cultivars for the Pacific Northwest

We discussed the benefits of harvesting mummies.

We discussed the benefits of harvesting mummies.


Responses from Surveys:

15MB

Most growers had some presence of mummy berry in the field. With most participants falling into the 1-15% range.

15Compare

Overall, mummy berry levels were “about the same” in comparison to last year.

15Mulch

Most growers report that they are currently mulching for disease control.

15Depth

Most growers mulch 1-2 inches.

15Timing

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!

15Type

Of course, Douglas Fir Sawdust is a favorite among mulch options.


Answers to Mummy Berry Questions:

Mummy berry infected fruit

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.

With the right environmental conditions, this mummy will produce an apothecium (fungal fruiting body, like a mushroom).

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.

Stipe and Apothecium

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.

Mummies Breaking Dormancy

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.


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