Natural Defense
Health From the Inside Out
By Rachel Foster 1/12/06

Organic growers have long understood that a healthy, living soil is vital to plant health and productivity, and that compost nourishes plants in ways that cannot be fully explained by its nutrient content. Increasingly, scientific research is providing explanations for some things we've observed or simply taken on faith. Small scale gardeners and farmers may not get very excited about these discoveries: Chances are they are getting the results they want just by working as much as possible with nature, no other explanation necessary. But science may have a lot to offer anyone who aims to refine, define and apply organic methods on a larger scale in an effort to make conventional farming less destructive.
Today, researchers are very interested in biologically based control of pests and diseases. Many natural, plant-made compounds like neem, rotenone and pyrethrin have been in use for a long time, as have organisms such as Bt and milky spore disease. More recently, it was discovered that applications of compost tea to plants growing in industrial monocultures can induce a complex "biofilm" of microscopic flora and fauna that protects plants in more natural situations from infection by destructive fungi and bacteria.
Scientists are also examining compounds underlying a plant's own, internal natural defenses. Salicylic acid (from which chemically similar aspirin is derived), is made by many plants to activate a spontaneous response to bacteria, viruses and fungi that scientists call Systemic Acquired Resistance (SAR). Applying aspirin water to soil and foliage apparently accelerates this vegetable equivalent to our own immune system, boosting plant health and aiding in germination, growth and productivity.
Also involved in SAR are the hrp genes, named for a sort of first line defense called Hypersensitive Reaction (HR): plant cells infected with bacteria collapse and die, immobilizing the intruders and blocking the spread of further infection. The product coded for by one hrp gene (derived, ironically, from the fungus that causes fire blight) is named harpin protein. When harpin was placed in a few of the intercellular spaces of tobacco, tomato or geranium leaves, it mimicked HR. What's more, untreated leaves of the same plants became immune to a variety of pathogens, meaning harpin was eliciting the more generalized SAR.
Conveniently, researchers found that topical application of harpin (spraying, for example) also triggered SAR, and it did something else, too: harpin-treated plants grew larger and faster than untreated plants. This effect was later confirmed in field tests, where growers found that harpin also accelerated ripening and improved yields from cotton, citrus fruit, peppers, strawberries and tomatoes. There are indications that harpin may ward off insect damage, too, and it is worth noting that pests and pathogens shouldn't become resistant to harpin protein -- or salicylic acid -- as they often do to conventional pesticides, since the former protect by acting on the plant itself, not directly on the pests.
Harpin protein is available from Eden Bioscience as the trademarked product Messenger. It is apparently non-toxic, is not absorbed by the plant and degrades rapidly, leaving no detectable residue. Since transgenic technology is used to produce the harpin protein, it isn't compatible with Organic (capital O) standards, but it does have the potential to reduce pesticide use in conventional farming and home gardens.
At a retail price of about $12 for three packets, each making one gallon, it's a lot more expensive than aspirin. And in informal tests by master gardeners, aspirin water (three tabs in four gallons), out-performed commercial biostimulants (not including Messenger) in growing vigorous, healthy plants. Try it on your disease prone roses or heirloom tomatoes -- and compare the results with those of compost tea, perhaps?
Yoga enthusiasts (myself included) say you can boost your own natural resistance by doing yoga. Now Sasquatch books has published a sweet little book on yoga especially for gardeners. Gardener's Yoga: Bend and Stretch, Dig and Grow by certified yoga instructor Veronica D'Orazio is a colorful volume of fully illustrated, gentle poses designed to keep your body happy while you work. The drawings are lovely and the instructions seem clear, accurate and helpful.
The book is divided into three series of poses to do before, during and after bouts of gardening. It makes no claims about the immune system, but as it says in the introduction to the warm-up section, "Start from your own center. Breathe and gently open the body and focus the mind for the day's demands. This will help your garden grow more than even the highest grade mulch!"