Environ. Horticulture, Pears, Cherries, and Viticulture
University of California
Environ. Horticulture, Pears, Cherries, and Viticulture

Strawberries

Moving pathogens in infested soil on equipment

Mark here - hey folks this concept of transmitting fungal inoculum from field to field on people's feet and equipment has been one I've been talking about for a while, and now here you have the scientific evidence from some of our finest scientists at the UC.  Really appreciate the two of them sharing these important results with us.

 

Soilborne diseases are caused by pathogens that reside in soil, such as Fusarium oxysporum, Macrophomina phaseolina, and Verticillium dahliae. They can survive for long periods of time as resistant structures. For this reason, soil carried on equipment can be a source of inoculum. To demonstrate this, we did an experiment in which a tractor was driven through a field where a pathogen was present. We sampled soil attached to the equipment to test for the pathogen. We also had a person walk through the field, and sampled soil attached to his boots.

The trial was run in February 2020 at the Plant Pathology Research Farm on the UC Davis campus. The field we used had an established population of Fusarium oxysporum f. sp. lactucae, the cause of Fusarium wilt of lettuce. We quantified inoculum as colony forming units per gram of soil. Colony forming units (CFUs) are either survival structures or crop residue colonized by the pathogen. Using this measure, the infested field had 243 ± 154 CFUs per gram of soil. This represents the average ± the standard error (a measure of variation across replicates). Soil collected from tractor wheels and the tiller confirmed the presence of the pathogen at 60 ± 19 CFUs per gram. The pathogen was present at 56 ± 18 CFUs/ per gram of soil removed from boots.

Infested soil on equipment or boots could introduce the pathogen to a new location. For this reason, it is advisable to wash soil off of farm equipment and shoes before moving between fields. This should be done routinely and not just when a field is known to have a pathogen. A pathogen may be present in a field, but not at levels high enough to cause disease. Consequently, no field should be assumed to be free of pathogens.

 

Tractor in the experimental plot infested with Fusarium oxysporum f. sp. lactucae.
Tractor in the experimental plot infested with Fusarium oxysporum f. sp. lactucae.

Soil brushed from tiller and tractor tires onto a plastic tarp.
Soil brushed from tiller and tractor tires onto a plastic tarp.

Soil brushed from tiller and tractor tires onto a plastic tarp.
Soil brushed from tiller and tractor tires onto a plastic tarp.

Collecting soil from boots.
Collecting soil from boots.

Posted on Wednesday, April 15, 2020 at 12:52 PM
  • Author: Ana Maria Pastrana
  • Author: Tom Gordon

Quotes in New Articles on California Strawberries in the Press

While I do enjoy the company of my family and others here at home during the shelter in place order, nevertheless sitting around on my can all day just writing, reading and talking on the phone isn't exactly what I signed up for folks.

Still, it's a time to be productive, and I've had some calls with resulting quotes in articles in the press.

The first from Laura Poppin in the Scientific American concerns what berry producers are doing to adapt to the restrictions of social distancing and virus transmission mitigation.  As expected, growers have adapted their operations:

https://www.scientificamerican.com/article/the-effects-of-covid-19-will-ripple-through-food-systems/

The other is a lengthy article by ag writer Tim Hearden from the Western Farm Press about the what the way forward for the California strawberry industry might look like, and quotes extensively from my review of the book "Wilted" by Dr. Julie Guthman:

https://www.farmprogress.com/farm-operations/resilient-strawberry-industry-faces-new-challenges?NL=WFP-01&Issue=WFP-01_20200323_WFP-01_358&sfvc4enews=42&cl=article_1_b&utm_rid=CPG02000000698567&utm_campaign=47755&utm_medium=email&elq2=a427d1d467184248a4480d416b9fd955

Nice to see interviews here with local grower Peter Navarro and fellow scientist Steve Fennimore.

 

 

Posted on Thursday, March 26, 2020 at 10:18 AM

Working from Home but Not Worse for Wear

As with my other colleagues from the UCCE, I am working from home to comply with the state order to shelter in place.

Doesn't mean I have to not enjoy the time here in the house, for example take a look at the tasty fruity chocolate strawberry snack my wife and I shared yesterday.  

So you all know, I am commited to being ONE HUNDRED PERCENT AVAILABLE by email and phone, and in the field for certain permitted circumstances and tasks.  If I haven't got back to you recently, it's because I was involved in a deluge of calls and communications last week with the County and UC organizing our effort to work remotely. 

Now we are all settled in, the winds have begun to fill our sails and we are once again underway.

thumbnail IMG 0955
thumbnail IMG 0955

Posted on Monday, March 23, 2020 at 12:33 PM

Hurray for the Scientists!

You all know the image of US Marines planting the US flag in the rocky soil of Iwo Jima in World War II.  Cartoonist Mike Luckovich has turned this iconic image into one depicting those who are on the front lines today of the battle against coronavirus - a first responder, a nurse, a doctor and yes a scientist.

 

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Posted on Saturday, March 21, 2020 at 9:41 AM

So This is Lewis Mite

Thanks to some sharp eyed grower colleagues - and well equipped with some impressive hand lens and field microscopes I might add - I got my hands on some good Lewis mites and was able get some pictures.  Truly, these do look different than twospotted spider mite.  Checked out with UCCE colleague Surendra Dara for confirmation and yes, we have our Lewis mite.

See photo below.

Lewis mite from strawberry field in the vicinity of San Andreas Road.  Note how spots run the length of the body and somewhat geometric appearance of the body.  Also smaller when compared to twospotted mites.
Lewis mite from strawberry field in the vicinity of San Andreas Road. Note how spots run the length of the body and somewhat geometric appearance of the body. Also smaller when compared to twospotted mites.

UCCE stock photo twospotted spider mite.
UCCE stock photo twospotted spider mite.

My own photo, twospotted spider mite.  Spots are restricted to shoulders and are large in comparison to body.  Larger and rounder than Lewis mite.
My own photo, twospotted spider mite. Spots are restricted to shoulders and are large in comparison to body. Larger and rounder than Lewis mite.

Posted on Thursday, March 19, 2020 at 2:30 PM

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