This is an integrated project of nematology, economics and dairy science to implement novel preplant soil treatments to almond and walnut to reduce the negative long-term effects of the…

The Regents of the University of California at Riverside received a $622,716 project grant from the U.S. Department of Agriculture's National Institute of Food and Agriculture under the Agriculture and Food Research Initiative (AFRI) program (CFDA 10.310), effective September 1, 2025, through August 31, 2028. This integrated nematology, economics, and dairy science project will develop and optimize cost-effective anaerobic soil disinfestation (ASD) treatments as sustainable alternatives to methyl bromide fumigation for almond and walnut production. The research aims to reduce nematode populations in soil using lower-cost organic amendments such as tomato pomace and anaerobically digested dairy manure, while simplifying application methods to eliminate the need for totally impermeable film and drip irrigation infrastructure. By reducing treatment costs from approximately $6,000 per acre to economically competitive levels, the project will provide California's nut crop industry with environmentally sound pest management solutions that comply with methyl bromide transition regulations.

The project directly supports the AFRI program's mission to advance agricultural science, improve crop production systems, and address sustainable natural resource management. Deliverables will include validated ASD protocols, cost-benefit analyses demonstrating economic feasibility relative to 1,3-dichloropropene fumigation, and technical guidance for growers implementing simplified, cost-effective soil treatment methods. Research will be conducted at the University of California at Riverside in Riverside, California.

This is an integrated project of nematology, economics and dairy science to implement novel preplant soil treatments to almond and walnut to reduce the negative long-term effects of the discontinuation of methyl bromide. Since the BAN of soil fumigation with methyl bromide for nematode suppression in nut crops in 2005, 1,3-dichloropropene (1,3-d) often in combination with chloropicrin has been used. Strict regulations because of environmental and human health concerns encumber the efficacy and economic feasibility of 1,3-d. Anaerobic soil disinfestation (ASD), incorporating easily decomposable organic matter into soil, maintaining high soil moisture saturation with drip irrigation lines under totally impermeable film (TIF), was adopted to suppress plant-parasitic nematodes for nut trees. ASD with rice bran at 9 ton/a reduced nematode populations 5 FT deep but cost $6,000/a (substrate: $3,000, TIF and drip irrigation: $2,000, and application and trash removal: $1,000) making IT non-economical. Tomato pomace and liquid manure cost less than rice bran, e.g., ~1/2 to 1/3 less (on a dry matter basis) for tomato pomace. Anaerobically digested liquid dairy manure had some nematode suppressive capacity. Application simplifications allowed foregoing the use of TIF and drip line while combining the entire application process in a single field pass. IT is the aim of this project to combine these cost savings to reduce expense of ASD, and make the method highly competitive with cumbersome, ineffective and expensive 1,3-d fumigation. This project aligns with the methyl bromide transition program by finding alternative soil treatment methods with less environmental impact and competitive efficacy.