Something is awry with your garden vegetables. They looked healthy enough a few days ago, but now the leaves are discolored and wilting. What could be wrong? After all, you’ve watered every day. Perhaps you’ve even given it some supplemental fertilizer. Yet it’s all for nought. Those vegetable crops are dying. What caused this to happen? The answer is simple. Disease. Just like the members of kingdom Animalia, the members of kingdom Plantae are also subject to the attacks of fungi, bacteria, nematodes, viruses, and mycoplasmas and all the havoc they wreak.
Diseases can be a serious problem in the vegetable garden. Disease-causing organisms can attack your seedlings and kill them before they emerge. They can also attack the stems, roots, and fruit of more mature crops. Left untreated, a bout of disease can devastate an entire crop.
All, however, is not lost. With proper care, diseases in your garden can be reduced or eliminated. The key is to stop disease before it starts, because once you notice visible symptoms, it’s already too late.
To prevent disease, keep in mind that for disease to have impact, three conditions must occur. First, the disease-causing organism must be present. Second, conditions must be right for the organism to infect, grow, and thrive. Lastly, the organism must find a home on a susceptible plant, e.g. a plant that is stressed, poorly cared for, or otherwise weakened. All you need to prevent disease infestation, therefore, is to take away any one of the legs from the disease stool. Then the disease cannot occur.
So how do you break the legs of the disease stool?
Crop rotation — Simply put, this means not planting the same vegetable crops in the same place in your garden year after year. Many diseases, such as clubroot and black rot (both of which affect Brassicas), can remain viable in the soil for at least seven years. So if you plant your kale, mustard, broccoli, Brussels sprouts, etc. in the same spot each year, you run the risk of repeatedly infecting your plants with these diseases. But if you move them to another part of the garden, then, you take away one of the legs (e.g. the susceptible plant) from the disease stool
Sanitation — This simply means practicing good garden hygiene. Some diseases can overwinter on infected plant parts. If you leave these laying around, then you run the risk of infecting your soil with these disease organisms, and then, by extrapolation, your plants. So clean up all spent plant parts at the end of the year. Clean up the weeds as well, because several diseases use weeds as their transfer agent. Lastly, if you smoke, don’t do it around your tomato plants. Tomatoes are susceptible to the tobacco mosaic virus, which can sometimes survive the tobacco-curing process. Touching your cigarette and then touching your tomato plants introduces the virus into your garden (e.g. leg number one of the disease stool). If growing conditions are right and the plants are stressed, then all is ripe for a mosaic blowout.
Water your garden in the morning or early afternoon — Watering in the early part of the day allows plenty of time for the sun and wind to dry wet leaves. Watering in the late afternoon or evening, especially in the early spring exposes the plant to cold and moisture — exactly the right kind of conditions for disease-causing fungus to develop (leg number two of the disease stool).
Leave adequate space between your plants — If plants are planted too close together, then the air circulation around them is reduced. Combine reduced air circulation with wet plants, and you’ve created a playground for the fungi (e.g. the proper conditions for disease to develop).
Plant vegetable plants at the proper time and at the right soil pH — Vegetable crops such as tomatoes, cucumbers, or beans grow grow best in warm summer weather. Blueberries grow best at a soil pH of 5.0. If you attempt to plant tomatoes, cucumbers, and beans in the early spring, or if you try to grow blueberries when the soil pH is greater than 5.0, they will perform poorly. Just as you feel stressed if the weather is too warm or cold, plants will also feel stressed if the environment around them is wrong. And just as we humans are more susceptible to getting sick when you’re under stress, a plant is, likewise, more susceptible to the ravages of disease when they are under stress.
So if you want to keep your fruit and vegetable crops healthy and disease-free, then follow the old stage saying and “break a leg”. Break all three if you can, and you’ll never again have to experience the heartbreak of disease destroying your plants and making a mockery out of all your garden efforts.