Gardening Articles: Care :: Pests & Problems
Cole Crop Disease Prevention
by National Gardening Association Editors
Some gardeners complain that their cole crops are constantly hit by diseases. Although you can't always do anything about them, understanding how diseases strike can help you get on the road to healthier crops.
The number and complexity of diseases possible in the garden might seem overwhelming, but consider the following: three things are necessary for a disease problem -- a susceptible plant, a disease organism and the right weather and environmental conditions.
This simple reminder applies to all vegetables, and it also helps to explain why cabbage family diseases can be light one year and troublesome the next. If one of the three requirements is missing, you can't have a problem. It's as easy as that.
Unfortunately, there are usually plenty of disease agents in the garden and a number of susceptible plants. So the weather is often the key factor in determining whether a plant will remain healthy or contract a disease.
Watch for signs of disease and practice the following 10 basic steps to safeguard your cole crops. It's especially important to be on guard during extended wet weather, because most diseases flourish during cool, wet periods. Stunted plants, blotchy or spotted leaves, drooping foliage or changes in color -- these and other signs indicate plants may be diseased.
Ten Steps to Healthy Plants
- 1. Crop rotation is probably the most important precaution a home gardener can take. Some disease organisms, such as those that cause yellows and clubroot, can live in the soil for many seasons. Depending on your garden size and its exposure to the sun, you might be able to solve a persistent problem with a three-year rotation plan. Don't plant any cole crop in the same garden area for three seasons. This should take care of any recurring disease problems. To be on the safe side, rotation is a must, even if your plants are perfectly healthy.
Crop rotation is especially important in the South and the Central states, where nematodes can be a big problem.
- Grow disease-resistant varieties that have proved to be reliable in your area. Check with your county extension agent for his or her recommendations if you have questions.
- When shopping for transplants, check for disease symptoms: stunted plants, blemished or yellowing leaves, wilted foliage. Also, check the undersides of leaves to be sure there are no aphids present.
- Plant crops in well-drained soil where they're sure to get plenty of sun. You can improve drainage by adding lots of organic matter to the soil and by planting on raised beds. Plants whose roots or foliage are constantly wet are more vulnerable to disease and insect attacks than those in drier spots.
- Use mulches to keep hard-hitting rain and irrigation water from splashing soil and disease organisms up onto plant leaves.
- Stay out of the garden when plants are wet in early morning or right after a rain or watering. Don't risk passing waterborne diseases from plant to plant.
- Watch for and control problem insects in the garden. Many aphids and some beetles can spread diseases, and certain larvae do extensive damage by chewing plants. Check the following section for insect descriptions and recommended controls.
- Pull up and destroy badly diseased plants to reduce the population of disease-causing agents. If you pull up sick cabbage plants, for example, and rotate the crop to another part of the garden next season, you may avoid that disease completely in the future.
It's not wise to compost seriously diseased plants. Although an active compost pile will heat up a great deal, you just can't be sure that the temperature will be high enough to kill harmful organisms. Burn or discard unhealthy plants.
- Keep your garden clean and weed free throughout the growing season and clean up crop residues immediately after each harvest. This eliminates places where diseases and insects thrive, and it is one more assurance of healthy plants.
- At the end of the season, make sure the entire garden is "put to bed" properly. Residues such as corn stalks, and bean and tomato plants that are left standing or lying on the ground make it easier for disease organisms and insects to live through the winter. Chop up and turn plants under or add them to your compost pile.