By A.J. Bailey, Master Gardener, Colorado State Cooperative Extension, Denver County
The outpouring of concern for the environment has touched almost everyone, including Rocky Mountain gardeners.
While gardeners always have been among the more environmentally conscious groups, most are thinking even more seriously about alternative means to control insects and other pests.
Now, instead of automatically spraying when an insect is spotted, most gardeners stop to ask if the pest is causing enough damage to warrant control. Some insects cause cosmetic injury only, leaving the plant's health intact. In this case, some gardeners are deciding they can live with the injury. The cone-like structures formed on Colorado blue spruce by the Cooley spruce gall adelgid is one such example.
Whether the introduction of pesticides into the environment is worth the time and the possibility of killing non-target insects also is of concern. Few chemicals are selective enough to only kill the problem pest. That leaves gardeners to weigh the benefits of spraying against the possible destruction of beneficial insects and other possible environmental impacts.
Perceptive gardeners consider the plant's age when it is attacked. Cabbage can tolerate a heavier infestation of cabbageworms and tomatoes can handle an onslaught of flea beetles when these plants begin to mature. An attack during earlier stages of development can severely injure or kill plants.
Although manufacturers have responded to the need for "safe" insect control, gardeners shouldn't assume a natural insecticide is completely safe. Some potent poisons occur in nature, and any insecticide must have some degree of toxicity to kill insects.
Rotenone, for example, derived from the root of a tropical plant, is widely marketed as a natural or organic insecticide. It actually is more toxic than diazinon (a commonly used man-made insecticide that has been removed from sale nationwide because of its potential to harm children and wildlife). This does not mean that rotenone shouldn't be used, only that it be used with the same caution as any pesticide.
Other insect-control strategies include hand-picking, the use of barriers such as floating row covers, and the use of sticky or baited traps. These can be used by themselves or in combination with other control techniques, including the most basic one, which is growing a healthy plant that resists pest attack.
As gardeners learn more about insects they begin to reject the "only good bug is a dead bug" mentality. It is a complicated world when it comes to pests and beneficial insects. To learn more about the "good guys", contact your local Colorado State University Cooperative Extension. Ask for the fact sheet "Beneficial Insects in the Yard and Garden."
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010