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Soil Pasteurization for Control of Coffee Root Knot Nematode

Grant Recipient:

University of Hawaii
CTAHR
Cooperative Extension Service, Hawaii County

Project Period:

19 months: August 2000 - March 2002

Principal Investigator:

Melvin S. Nichina, Marcel M.C. Tsang, Gaillane T. Maehira and Virginia Easton Smith

Description
The termination of sugar operations on Oahu, Maui and Kauai and pineapple operations on Molokai has released 250,000 acres of land for alternate crop production and another 125,000 acres on the big island of Hawaii. Coffee has been identified as a potential replacement crop and many of the displaced workers have turned to coffee production as an alternative crop. Historically, coffee production in Hawaii was limited to the Kona district on the big island. During the 1999/2000 period, the Island of Hawaii reported 3,200 planted acres on 635 farms. The typical Kona coffee farmer grows coffee on about five acres in very hilly terrain, primarily between 600 to 2,000 feet elevation. In the late 1980s, producers began to notice a disease problem referred to as "transplant decline," "replant problem," or "Kona wilt." The cause was identified as a new nematode of coffee, Meloidogyne konaensis. Growers were told to start new coffee plants from seed and grow them in sterile media. Coffee plants are typically grown in quart sized bags for about 9 months to about 2 to 3 feet in height before transplanting to the field. Tree populations range from 500 to 600 plants per acre. The cost of sterile media, which must be imported into the Island, is approximately $.50 per plant or about $300.00 per acre. These nematodes can be controlled by fumigation or heating with steam but these treatments are prohibitively expensive. Fumigants such as methyl bromide are toxic to the environment. An alternative method is through heat pasteurization. In an earlier project funded by EPA OPP/BPPD and AFT, the researchers developed a prototype solarization unit to sterilize potting soils for nurseries in Hilo. This project will adapt the unit to conditions in Kona and determine the optimum tube diameter necessary to eliminate both the juvenile and egg stages of the Kona coffee nematode.

Project goals and objectives
1). To determine the optimum copper tube diameter for the solar pasteurization unit to heat soil to 70C (158F) in the coffee growing area of Kona.
2). To evaluate the efficacy of solar pasteurization against both juveniles and eggs of the Kona coffee root knot nematode (Meloidogyne konaensis).
3). To measure the growth differences in coffee plants between pasteurized and untreated soil.

Outcomes
Initial tests to determine the optimum tube diameter for the solarization unit showed that either the 9 or 12 inch tubes would work in Kona. However, to insure that weed seeds were killed as well as nematodes, the researchers selected units with 9 inch tubes to consistently maintain temperatures over 150 degrees F. They were able to demonstrate that local soils could be pasteurized by solarization units and used in place of imported potting soil.

Project Links
More information on the solar soil pasteurization unit and how it has been modified and improved since this demonstration model was constructed can be found at:
hilo.hawaii.edu/academics/cafnrm/faculty/Solarproject.php

American Farmland Trust