Katharine D. Widin was the plant health columnist for Minnesota Horticulturist and Northern Gardener for 32 years, covering every bug and disease known to haunt gardeners. And, while she knew which chemicals would eliminate various pests, she always suggested embracing less damaging strategies for pest control first.
In one of The Good Gardener books the hort society published in the 1990s, she narrowed these strategies for pest control down to five tips.
Start with healthy plants. When you are buying plants at a nursery or garden center, make sure they are healthy. Plants that are scraggly, yellowing, overgrown, crowded or seem to have received less than stellar care may harbor diseases or be susceptible to disease when they get in your garden. Inspect plants for signs of wounds or egg masses. Once purchased, give plants the best shot at a healthy life by placing them in the recommended location in terms of sun, water the properly and give them the right amount of fertilizers.
Choose resistant varieties. Plant diseases continue to evolve and happily more so do ornamental and vegetable plants. If you have had a problem with wilts, blights or mildew, look for varieties labeled for disease resistance. The new impatiens varieties that are resistant to downy mildew on impatiens are an example of these new tougher varieties.
Know what you are dealing with. "Knowing the identity of the insect or disease which is attacking the plant, the recommended control, and the proper timing of implementation are among the most important aspects of effectively controlling a problem. Many problems are fleeting and need no action from you. Today apps and online resources can be very helpful in identifying a problem. However, be sure the advice is sound. We look to university sources for information, whenever possible.
Rotation and sanitation. For annual plants, including vegetables, moving them around the garden from year to year is a good way to prevent insects and disease from building up in the soil. If a plant is diseased, clean up around it in the fall to remove leaves, spent fruit and other items that may be harboring spores or fungi that will come back the following year.
Organic controls. If the situation requires action, consider first organic strategies for pest control. Bt (Bacillus thuringienses) is an option. Some insecticides, such as insecticidal soaps, degrade rapidly yet are effective controlling insects, she noted.
What are some of your favorite strategies for pest control without using chemicals?