Development and Implementation of On-Farm Biological Soil Disinfestation to Manage Soilborne Diseases In Organic Strawberry Production Systems

View the project final report

Commodities

• Fruits: berries (strawberries)

Practices

• Crop Production: biological inoculants, cover crops, nutrient cycling
• Education and Training: demonstration, on-farm/ranch research, participatory research
• Pest Management: biological control, integrated pest management, mulching - plastic, mulching - vegetative
• Production Systems: holistic management, organic agriculture
• Soil Management: green manures, organic matter, soil microbiology

Strawberry growers seek methods to increase yields and to manage soilborne diseases and pests. There is increased interest in eliminating fumigants or transitioning to organic practices. We explored the on-farm utility of using a method called “anaerobic soil disinfestation” (ASD) to treat soils. The method includes the use of a highly labile carbon source incorporated into soil within beds covered with plastic mulch. Then the beds are flooded, using the drip tape assembly, to induce anaerobic conditions that are speculated to result in a decrease in strawberry pathogen and weed seed populations. This on-farm research assessed the ASD method and took data on microbial communities, plant growth and yield.

Introduction

Organic growers, and conventional growers who desire to eliminate soil fumigants, have very few options for managing soilborne diseases in high value specialty crops. Crop rotation and host resistance play a critical role in managing soilborne pests. Many strawberry growers do not have opportunity to rotate crops for the length of time that is best and/or need to grow their “money” crops on their “money land” e.g. superior soil types or under high tunnels. Likewise, many specialty crops do not have advanced host resistance to the major and often too common soilborne diseases in NC and the South. Therefore, alternative management practices need to be developed and incorporated into a sustainable IPM-based management plan. We seek to research a method called Biological Soil Disinfestation (BSD) or Anaerobic Soil Disinfestation (ASD) to manage soilborne diseases in strawberry production.

Anaerobic soil disinfestation (ASD) methods were first developed in Japan where the researcher sought an alternative soil treatment in areas not conducive to soil solarization or other economical soil disinfestation processes (Shinmura, 2000; Momma, 2008). A group in the Netherlands also developed a modified protocol in field production and obtained superior control of Verticillium wilt, reducing inoculum levels by up to 85% for up to 4 years after soil treatments, compared to non-treated soil. In the Netherlands, they called it Biological Soil Disinfestation (BSD), which emphasizes the interaction between soilborne pathogens and beneficial or antagonistic microbial communities (Blok et al., 2000; Goud et al., 2004; Messiha et al., 2007). Since then, both regions have seen extensive expansion of the method to control a range of soilborne pathogens in many specialty crops, particularly strawberries and solanaceous and cucurbit vegetables. Recent research in the U.S., Florida vegetables and California strawberries, has shown promising results when adapting this technique to raised-bed, plasticulture production systems (Butler et al. 2010; Shennan et al. 2010). In California ASD in strawberry production using flat field production or raised beds (Shennan et al., 2010) proved successful. They found mortality of the Verticillium dahliae microsclerotia was 98% in ASD treated areas, whereas the counts increased in non-treated areas. This work is now supported by the California Strawberry Commission – as well as the USDA-NIFA MBT program (J. Muramoto and C. Shennan, personal communication; Shennan et al., 2007; Butler et al., 2010; 2012). The system relies on incorporation of a labile carbon source (e.g. wheat bran, rice bran, molasses, fresh plant residues potentially grown on site) to stimulate soil microbial growth and respiration, saturation of the topsoil to reduce soil oxygen, and tarping with plastic to limit gas exchange during a three to six week pre-plant treatment period. Control of plant pathogens and to some extent, weeds, is largely due to the formation of organic acids and volatile compounds during the anaerobic breakdown of the added C source, as well as through potential biocontrol mechanisms occurring during shifts in microbial community composition (Momma 2008). Therefore, the research and practical experience developed in the Netherlands and Japan and the current work begun in California and Florida offers substantial promise that the ASD system for managing soilborne diseases (and other pests) will be effective in Southeast strawberry production systems. We believe this system is highly adaptable to our strawberry production systems because growers generally do not grow an economic crop during the summer prior to fall planting, providing an ideal window for advanced farming system management practices. Also, most of our growers desperately need a systematic and systems-based mechanism to enhance the organic matter content of their soils.

We proposed to implement and develop anaerobic soil disinfestation (ASD) as a mechanism to suppress soilborne pathogens, enhance soil health and increase crop productivity in strawberry production systems.