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Journal American Rhododendron Society

Current Editor:
Dr. Glen Jamieson ars.editor@gmail.com


Volume 33, Number 4
Fall 1979

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Natural Insect Control Versus Pesticides
Basil C. Potter, Port Ewen, New York

        Insects are not without purpose. They are definitely a part of nature's overall plan.
        Diseases also have a purpose, part of which is the elimination of the weak, and allowing only the survival of the fittest.
        Man cannot completely control insects with his chemical poisons, but these poisons, unless their advancing use is scientifically controlled, can destroy our soil and our food crops.
        Insects and disease, under nature's supervision, have served the wild plant kingdom and mankind's food supply from before the Neolithic man up to the beginning of the twentieth century when man decided to declare war on insects and to fight them with poisonous chemicals.
        This fight has continued for nearly a hundred years. After the expenditure of billions of dollars on research and new chemicals, the insects are still with us and serving the purpose they were created for.
        We do know that, in the wild, natural control prevails. However, just how nature does not fully understood. Sure we know that insects prey on each other in various ways, and that birds and animals feed on them. But what about a plant's genetic ability to protect itself? Dr. Leach tells us some rhododendron leaves are poisonous to animals.
        A few years ago while looking over a bed of R. chrysanthum in flower, attention was focused on a beetle that had just landed on a R. chrysanthum leaf. The way it crawled around seemed somewhat unusual. Finally, it came to the leaf's tip and started to feed. After it had ingested a one-eighth inch chunk of the leaf, it paused for a few moments, then fell to the ground dead. That happening raised the question, was the R. chrysanthum leaf toxic to the beetle or was its death due to other causes?
        This bed of R. chrysanthum was grown from seed collected in the wild and was twelve years old at the time of the beetle observation, and at no time have these plants needed protection from insects or disease. Generally speaking, species grown from seed collected in the wild need no protection from insects.
        It has been noted that feeding insects avoid such species. Could it be that the insects are forewarned that the species leaf would not be good for them? If so, how do they receive that warning? Is it an atom signal or is it a chemical odor emitted from the species leaf? If it is an odor emanating from the leaves, could we manufacture that odor in a non-poisonous spray for nonresistant hybrids?
        There is great concern over the use of chemical poisons on food crops. Now we know that liquid nutrients are absorbed by the leaves of rhododendrons and carried throughout the plants internal system to its roots.
        If we are alarmed over the use of poisons on the food we eat, should we not be concerned about poisons we apply to our rhododendrons? This concern led to an experiment that involved moving several hundred young rhododendrons from soil that had received chemical poisons in various forms for years, to land filled in with clean bank run subsoil. Beds with six inch side boards were built, and four inches of peat moss plus nutrients were tilled in. When the planting was completed, the beds were mulched with hardwood chips. These plants received adequate moisture throughout the first season. At the end of the growing season, the results, by comparison, were better root development, improved vigor, superior branching, leaf color, and more flower buds.
        Sure there could be other factors involved. However, more time is needed. The hardwood chips used on the new beds were composted on rich woodland soil and probably inoculated the new beds with an ample supply of micro organisms.
        Each of the new beds was individually lath shaded. Surplus hybrids were bedded in the open, and were slightly superior to those under shade. Also they suffered no leaf damage from sun or insects.
        In view of the fact that natural control seems to be working now in both mini nurserys, one wonders if the average rhododendron fancier in the Northeast really needs to use pesticides.
        In support of this theory, may I refer to a prime example: A close friend of mine built a new home on a half acre plot and decided to landscape his place with rhododendrons, leaving only a few patches of lawn. This planting required something over two hundred rhododendrons, and is now slightly more than ten years old. At no time have these rhododendron ever required or received a spray of insecticides or fungicides, nor have they ever needed one.
        Each year this garden has put on an astonishing floral display and has attracted wide spread attention. The owner applies a new layer of hardwood chips each spring plus a hand full of 5-10-5 to each plant in early spring. That and the normal dead heading add up to all the care given this planting.
        In another locale, high on the side of a mountain, deep in the Catskill Mountains, a naturalist built an A frame home and landscaped it with a goodly number of rhododendrons. Needless to say, no poisons were ever used on his plantings. I was privileged to see his rhododendrons once a year. Up until his recent death, he was a little known member of the A.R.S. I mention this because natural control worked perfectly for his plantings in the wild.
        In 1933, we planted two Iron Clads in front of our home and these plants have bloomed heavily ever since. They are dead headed each year and cut back from time to time. Otherwise, they receive no other care of any kind. These plants are a positive example of natural control, for, no observable leaf damage has ever been noted.
        Nature gave us beautiful wild rhododendrons in pure colors and a genetic system that allows us to breed them for adaptable hardiness, color, bush habit, insect and disease resistance, so lets not poison them and the earth we want them to grow in.


Volume 33, Number 4
Fall 1979

DLA Ejournal Home | QBARS Home | Table of Contents for this issue | Search JARS and other ejournals