Factors in pest and disease prevention
A well-balanced soil with plenty of decomposed organic matter is the basis for plant health.Most organic gardeners consider pests and diseases to be a symptom—as opposed to a cause—of poor plant health. From this perspective, pest and disease prevention focuses on plant health, which depends on three main factors: plant selection, soil health, and biodiversity.
Growing the right plants for your environment
Varieties that are well suited to your soil, rainfall, temperature, and other environmental factors tend to have better health than those that are not adapted to your conditions.
Soil health
Healthy soil is the basis for vibrant plants, and the basis for healthy soil is organic matter added as mulch or compost.
Biodiversity
A diverse garden is less prone to outbreaks of pests and disease than large, single crop plantings. Pictured: A diverse food forest of banana, cassava, taro, jackfruit, jaboticaba, and fig (left to right).Growing a mixture of different plants and varieties tends to suppress pests and diseases relative to growing a single crop on a large scale.
If you already have a pest or disease problem (you are past the point of prevention), then there are organic options for treatment. When faced with such problems, many gardeners opt to start over with a different crop or plant variety.
Books
Eco-Farm, An Acres U.S.A. Primer: The definitive guide to managing farm and ranch soil fertility, crops, fertilizers, weeds and insects while avoiding dangerous chemicals by Charles Walters. 2003 (3rd revised edition). Acres USA. A detailed, authoritative primer for the paradigm shift towards organic and sustainable agriculture.
Weeds, Guardians of the Soil by Joseph A. Cocannouer. 1980. Devin-Adair. Shows how weeds contribute to garden health and give clues as to soil conditions.
Web resources
CTAHR's Sustainable and Organic Program: http://www.ctahr.hawaii.edu/sustainag/
Soil Biology Primer: soils.usda.gov/sqi/concepts/soil_biology/biology.html
Hawaii Plant Pests and Diseases by Dr. Scot Nelson: www.plant-doctor.net
University of Hawai‘i Master Gardener program: www.ctahr.hawaii.edu/ctahr2001/UrbanGardenCenter/index.html
Craig Elevitch is director of Hawai'i Homegrown Food Network and an educator in agroforestry. His books include Agroforestry Guides for Pacific Islands (2000), The Overstory Book: Cultivating Connections with Trees (2004), Traditional Trees of Pacific Islands: Their Culture, Environment, and Use (2006), and Specialty Crops of Pacific Islands(2011) all of which promote diverse agricultural systems that produce abundant food.