The virus that causes the common cold is ubiquitous, yet we humans don't walk around with colds every day of our lives. Though I might have the germ in my body or come in contact with it when I leave my home, most of the time I'm symptom-free. I successfully repel the virus by maintaining general good health, eating well, and not running myself down.
In the same way that maintaining good overall health prevents me from coming down with a cold, keeping plants strong and healthy helps them fend off disease and insect attacks. Building the best soil you possibly can and placing plants in optimal conditions for sun, moisture, and companions to promote good health and minimize problems is a no-brainer. But when bugs or diseases strike, the first instinct of many gardeners is to turn to the treatment that kills the particular pathogen or insect affecting their plant, rather than examining environmental conditions. The state of non-health is understood to be a result of the the plant “catching” a disease, or the insects just suddenly showing up, and not of environment factors.
Root rot is a good example of a disease that is widely understood to be environmental. Under conditions of inadequate drainage, a plant’s roots begin to rot. While there are specific, known fungi associated with decaying roots, it is generally accepted that the best way to remedy the condition is to improve drainage or simply stop watering as much. The fact that the condition is usually referred to as simply root rot, and not by the names of the associated fungi, reflects the fact it's considered a problem arising from the plant's environment.
Often this is not the case. The names verticillium wilt and powdery mildew refer to groups of organisms. Leaf curl, the various blights, black spot, and canker use visual descriptions to provide disease names. If I say I have aphids or Japanese beetles or thrips, other gardeners know exactly what I mean, but there's no explanation of why I have an infestation embedded in the insect name; I'm merely reporting the organism I have observed.
As an amateur student of ecology I realize disease and decay are inevitable and I'm not going to claim that every insect and disease can be controlled by manipulating environmental factors, but I think it should be acknowledged that in many cases the disease or insect pests attacking plants are symptoms of underlying proplems. The best way to minimize problems in the garden is to create the optimal conditions for plant growth. Under such conditions plants can best ward off disease and withstand insect attacks with less effect on the harvest.
What if, rather than immediately attempting to eliminate the bug or pathogen, we examined growing conditions to identify plant problems? This requires accepting some level of disease and insects, rather than reaching for the poisons at the first sign of perceived problems. There are practical reasons for this in the case of insects: leaving the bad bugs alone gives the predatory insects time to show up and provide natural pest control. Most chemicals commonly used in gardens, even natural ones that break down quickly, kill indiscriminately, leaving a vacuum of insect life. This sets up conditions for the bad bug population to not only recover but explode. And while it might seem sacrilegious to allow diseased plants to remain in the garden, sometimes observing unhealthy plants can help us understand the garden better as a working ecosystem.
Observation can lead to creative solutions to disease problems. I've spent several years observing my raspberries which have some type of disease, probably fungal. I've noticed that berries in general do not like to stay in the same place. Black raspberries, when left unpruned, fall over and root, in essence “walking” to their new spots. Strawberries quickly crawl everywhere with their innumerable runners. New raspberry plants pop up all around their bed, and the new plants tend to be vigorous and healthy, leading me to allow this movement rather than fighting to keep the berry plants contained. Will it be possible to defeat their disease by letting the patch to migrate around the garden? I can't know for sure yet, but I look forward to experimenting. It means giving up some control over where plants are situated, but I'm comfortable with that.
I don't attempt to eradicate all disease from the garden with sprays and dusts, but observe to learn how the pathogen operates. Sometimes plants look terrible, but harvest isn't significantly affected. In other cases, removing just the affected parts is enough to solve the problem. If a plant is too far gone, I remove it completely so something else can be planted. A lot of time, energy, and unnecessary toxins are wasted to save lost causes. Observing and learning over time has helped me figure out the best way forward without ever having to resort to synthetic chemicals or even “organic” treatments.
Of course, learning as much as you can through internet or library research is important, but be aware that often advice is geared toward commercial operations, where crops are grown in monocultures with each plant genetically identical to the the next. Often under such conditions the only option to prevent great financial loss is the application of chemical pesticides, therefore that is the only solution presented. The home gardener growing under vastly different conditions should take such advice with a grain of salt. A certain disease or insect may be portrayed as devastating, but in reality may only cause superficial damage. Such injury might be catastrophic in markets that demand flawless fruits and veggies, but inconsequential to the home gardener. A few holes on my cabbage leaves are easily trimmed off and I can remove any pesky caterpillars before use. The same cabbage would be unsalable at a supermarket.
Most my gardening solutions are designed for the long term. I recommend letting go of the need to take immediate control and rid your plants of any and all deviations from the perfect. The presence of diseases or bad bugs doesn't necessarily mean your garden will be decimated. If you do experience massive destruction, work on environmental factors such as improving your soil and proper watering techniques first. And remind yourself: There's always next year.