Use Light Arms on Pests Before Turning to Heavy Artillery
One of the most controversial balancing acts facing gardeners is the use of pesticides.
Chemical control of insects first surfaced in the early 19th century, when a mix of lime or wood ashes and powdered tobacco leaves was sprinkled on plants to deter bugs. In the 20th century, pesticide use became indiscriminate. The assumption was that pesticides were the best way to control insects.
However, the question of whether pesticides could harm us and our environment became an issue. The book "Silent Spring" by Rachel Carson, published in 1962, raised public concern.
Carson's work and that of others expressing concern about the rampant use of toxic pesticides was a major force behind the development of safer ways to control pests.
Over the years, public concern about using a balanced and reasoned approach to pesticides gained more attention. A program called integrated pest management (IPM), which attempts to balance the use of pesticides, was developed with federal backing. These days, IPM, which calls for using the lowest-impact methods before turning to heavy-duty pesticides, is widely embraced.
But even before Carson, there was resistance to rampant use of synthetic toxic chemicals. Carl Orndorff, a Maryland grower and horticulturist for more than 70 years, used to laugh when we discussed the cutting-edge IPM program. He related a story to me about a method he developed in the 1930s called preventive pest management that involved common sense, proper placement of resistant plant material and monitoring pests. He referred to his program as the first IPM. His total pesticide expenses were 42 cents per acre annually in his years as owner of Kalmia Farms, the region's largest wholesale nursery in the late 1970s and 1980s.
"Silent Spring" reinforced Orndorff's balanced approach to pest control. Since then, sentiment has turned toward environmental stewardship. We don't want to live with pests, but don't want to be poisoned trying to control them. For example, homeowners who want golf-course-type turf have to decide how to balance that desire with the safety of children and pets.
In landscape gardening, there are two camps on pesticides: the chemically concerned, and those who can't get the high-quality results they want because of the chemically concerned.
The reasoning on one side is that there's no reason to apply a known toxic material unless absolutely necessary. On the other, the logic is that such materials have gone through rigorous laboratory testing, some with more than 30 years of positive results with no deleterious effects.
A sensible compromise is a basic tenet of IPM. "Wait and see" is a good approach, as long as you monitor and are willing to treat or replace if a problem gets worse.
Some plant problems are cyclical and last only several seasons. Pests can suffer from overpopulation, diseases, parasites and predators. For example, according to Len Phillips, editor and administrator for Online Seminars for Municipal Arborists, even though gypsy moths are not native to North America, they succumb to more than 20 natural predators, parasites and diseases.
We might have crossed another threshold with a decade of trees dying from dogwood anthracnose, when sprays held the fungus at bay only superficially. According to University of Maryland plant pathologist Ethel M. Dutky, fewer native dogwoods are developing anthracnose symptoms. Perhaps they developed or inherited resistance.