Instant biofumigation using natural products from papaya seed waste for sustainable management of soil-borne plant pathogens

Project Overview

Project Type: Research and Education
Funds awarded in 2020: $349,995.00
Projected End Date: 12/31/2023
Host Institution Award ID: G346-20-W7899
Grant Recipient: University of Hawaii at Manoa, College of Tropical Ag & Human Resources (CTAHR)
Region: Western
State: Hawaii
Principal Investigator:
Dr. Wei Wen Su
University of Hawaii at Manoa, College of Tropical Ag & Human Resources (CTAHR)
Dr. Stuart Nakamoto
U. of Hawaii Manoa, Human Nutrition, Food, and Animal Sciences
Dr. Koon-Hui Wang
University of Hawaii
Dr. Tao Yan
Dept. of Civil & Environ. Engineering, University of Hawaii at M

Adjusted (start and) end date per PI's request (one month shift later). -- JvS 5/28/2020

Information Products


  • Fruits: papaya
  • Vegetables: cucurbits, greens (lettuces)


  • Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research, workshop
  • Farm Business Management: new enterprise development, value added
  • Pest Management: allelopathy, biofumigation, biorational pesticides, integrated pest management

    Proposal abstract:

    Soil-borne diseases caused by fungi and nematodes bring about serious damage to many crops of agricultural importance. Conventional soil fumigation for controlling soil-borne plant diseases is most commonly based on synthetic chemicals many of which cause serious negative environmental impact and have been phased out. Biofumigation is an eco-friendly alternative for suppressing soil-borne pests and pathogens. Conventional biofumigation uses macerated green manures from glucosinolate-rich biofumigant plants, such as brown mustard, as soil amendments. This practice suffers from shortcomings that include costs and time associated with cultivating the biofumigant crop. Furthermore, cruciferous cover crops are often hosting common pests of leafy greens, and cover crop rotation is impractical for long-term orchard crops.

    In this project, we put forward a novel approach aimed at improving and simplifying the biofumigation practice. We will develop new “off-the-shelf” organic biofumigant products based on papaya seed wastes that are abundantly available in Hawaii to achieve instant and more precise biofumigation without the need for growing biofumigant cover crops. Papaya seeds contain a high level of benzyl glucosinolate that is enzymatically hydrolyzed via myrosinase to form benzyl isothiocyanate, which has potent pesticide activities against a range of soil-borne phytopathogenic nematodes, insect pests, and fungi. 

    Our central hypothesis is that ground papaya seeds can be applied as an effective natural soil fumigant, and the efficacy can be enhanced by optimizing seed processing, formulation, and fumigant application regimes. A secondary hypothesis is that the binary nature of the glucosinolate/myrosinase system can be exploited to achieve higher degrees of control over biofumigant delivery and activation, and thus improve dosage and bioavailability of the released isothiocyanate. These hypotheses are supported, in part, by our preliminary study, as well as data in the literature. We will work with our collaborating farmers to conduct a series of field tests with the papaya seed biofumigants on their farms. We will also conduct laboratory studies that integrate with the field tests to help develop a comprehensive understanding of the biofumigation process, and use the knowledge to refine the field tests to achieve high biofumigation performance in managing phytopathogens and promoting plant health.  

    The project team will continue to actively involve producers throughout the entire study via research, extension, and outreach activities, with the goal to make the proposed “instant biofumigation” technology readily adoptable by the farmers. Field trials of instant biofumigants will be conducted in collaboration with each of our three core participating producers. Educational workshops and field-day events will be held regularly, and mass and social media technology channels will be employed, to disseminate project findings to farmers and other agricultural professionals, and to solicit their feedback and suggestions.

    The key expected outcome of this project is effective management of soil-borne pests, using a natural and renewable fumigant made from underutilized, locally sourced, agricultural waste, based on a simple and environmentally friendly process. Development of papaya-seed biofumigants will reduce reliance on imported pesticides, while endorsing the concept of “reduce, reuse, and recycle” to promote sustainable agriculture and continuing growth of local farm community. 

    Project objectives from proposal:

    The goal of this proposal is to augment the efficacy of biofumigation, by achieving higher degrees of control over biofumigant delivery and activation to improve dosage and bioavailability of the released isothiocyanate, while keeping the cost of the system down by using raw materials derived from seeds of papaya wastes that are abundantly available in Hawaii. The proposed work on developing the papaya seed biofumigant technology builds on field tests (with papaya, lettuce, and pumpkin as the three test crops) to be conducted on collaborating farmers’ farms with close collaboration with the participating farmers. We also proposed laboratory studies that integrate with and refine the field tests to achieve high biofumigation performance. The proposed research has the following four specific objectives:  

    1. Evaluate the effect of papaya biofumigants in managing plant-parasitic nematodes and Fusarium wilt, and on plant health, in field studies. (Year 1-3)
    2. Optimize the papaya biofumigant system by integrating laboratory studies with the field studies, and assess impact of biofumigant application on soil microbial communities. (Year 1-3)
    3. Determine costs and benefits of the instant biofumigation technology. (Year 2-3)
    4. Disseminate information about the instant biofumigation technology to edible crop producers for soil borne disease management. (Year 1-3)

    This is a “long term” project. Our short-term goal, which is to determine field performance of the proposed papaya seed biofumigants (efficacy in managing soil-borne plant-parasitic nematodes and Fusarium wilt, as well as effect on plant health and microbial communities) and to characterize the biofumigation process, will be accomplished within the current proposed 3-year funding period. To bring the technology to full large-scale implementation, we expect additional optimization and field testing would be necessary which will be pursued upon completion of the current proposed 3-year study, for approximately another two years.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.