How to Manage Soil-Borne Disease in Berries

Mark Mazzola, a USDA-ARS Research Plant Pathologist, has done studies that center on the management of soil-borne diseases in strawberries using unconventional strategies.

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One of the options that has been examined for managing disease is anaerobic soil disinfestation (ASD). Analysis of this approach is part of a collaborative project that includes researchers from University of California, Santa Cruz; University of California, Davis; California Polytechnic State University; and the California Strawberry Commission.

Mazzola says ASD relies on the transformation of the soil microbiome, which leads to the production of metabolites that suppress specific pathogens.

According to a report on the research from UC Santa Cruz, ASD was developed as an alternative to methyl bromide fumigation to control a range of pathogens and nematodes. It can be broken down into three steps:

  • Incorporate organic material to provide a carbon source for soil microbes;
  • Irrigate the field to capacity; and
  • Cover with an oxygen-impermeable tarp to create anaerobic conditions and stimulate anaerobic decomposition of the organic material.

Understanding Soil Biology
In his conversations with various types of growers, Mazzola has concluded that virtually all are interested in knowing more about how soil biology impacts crop production, but there seems to be a lack of useful resources available to help growers fully understand the topic.

Mazzola says one of the major misconceptions he has encountered on various levels of expertise is that interactions between a plant and the soil microbiome are random. This can lead to less than optimal outcomes when attempting to use microbiology to enhance plant production, he says.

“Certainly the complexity of plant-soil-microbe interactions is an element that continues to be revealed as well as the roles that microbes have in directing items such as root development, flowering time, etc.,” Mazzola says.

For example, he explains that there is a relationship between a crop species and its capacity to be infected by a mycorrhizal fungus and thus facilitate the acquisition of phosphorus from the soil system.

“This information is of importance if a grower is considering the use of commercial mycorrhizal inoculants. Not all mycorrhizal fungi will form effective interactions with all plant species,”  he says. “To make matters more complex, these plant-mycorrhizal fungi interactions may be facilitated by other soil/rhizosphere microorganisms.”

Mazzola believes that managing the soil microbiome has benefits to the overall production potential of a cropping system and that most growers understand that.

“After all, there is great effort and expense invested toward improving ‘soil health’ through various inputs such as additions of carbon to soil (for example, compost),” he says.

However, Mazzola notes that the primary benefit of using such inputs is to achieve changes in the composition of the microbiome that, in turn, lead to improved plant health. He says that inputs do not alter the soil, per se.

“I believe soil health is a misnomer as the ultimate goal is improved plant production or health,” he says, “and what is being altered is predominantly the effective function of the microbiome.”