Growing- Healthy plants naturally protect themselves from virus and fungal infection by creating antiseptic compounds within their leaves in the same way our skin does. However, when environmental stress causes their natural immunity to fail it becomes necessary to sterilize the affected area removing all fungal and bacterial spore colonies until the plant returns to health. You can use a variety of organic oils to accomplish this. Including tea tree, rosemary, or garlic oils. If you have suspected a viral pathogen removing the affected plants and allowing the soil to solarize completely over one summer before replanting will usually stop the spread.
Most fungal and virus contamination is a result of creating an environment for it to thrive. Arizona has very low humidity/ high UV levels most of the year, and rates of spore and virus proliferation are fortunately lower in the desert environment. Once you create a humid micro-climate you make it easier for them to thrive here. Using natural immunity boosting compounds in the soil, like silica, neem, willow, humic and amino acid; combined with hygienic practices to minimize cross contamination, and a quarantine procedure in place for new plant material and infected plants makes the spread and colonization on spores less common.
Propagation- Saving seeds and taking cuttings requires a higher level of sterilization, cinnamon is a potent anti-fungal for seed saving, and alcohol must be used to sterilize all instruments prior to cutting and between plants/trees. Organic honey has beneficial properties when mixed with water and can be used in combination with root inoculation teas, killing potential pathogens, while allowing spores to colonize new roots.
Using completely sterile media like coconut, vermiculite or super heated soil mixtures will provide the best protection against transferring pathogens to new plants
Post-Harvest- The antiseptic qualities of plant material begins to decline almost immediately after harvest, they become breeding ground for everything they are contaminated with. As a gardener, you want to minimize the foods contact with pathways, shoes, unwashed hands, and even new soil if you are not sure it has been thoroughly heated. Washing produce before storage, and also before ingestion is always advised.
If you choose to sell or give away your produce, you should research and follow food protocol, including prevention methods for the spread of listeria, e. coli, and other dangerous pathogens that can result from unsanitary growing practices. Hair coverings and gloves are a simple way to control a lot of problems in the food and ag industries. Complete sterilization can be achieved with an ozone generator, but will kill beneficial insects and people, so use with extreme caution post harvest.