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

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

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