EGARDENING 

References

Pesticides in the garden
Part 2: Not so good for me
by Catherine Kavassalis 

"The great expectations held for DDT have been realized. During 1946, exhaustive scientific tests have shown that when properly used, DDT kills a host of destructive insect pests, and is a benefactor of all humanity. Pennsalt produces DDT and its products in all standard forms and is now one of the country's largest producers of this amazing insecticide.  Today, everyone can enjoy added comfort, health and safety through the insect killing power of Pennsalt DDT products...

KnoxOut for the home--helps to make healthier, more comfortable homes...protects your family from dangerous insect pests.  Use KnoxOut DDT powders and sprays as directed...then watch the bugs 'bite the dust'."

(Pennsylvania Salt Mfg. Co. advertisement in LIFE Magazine, 1946)

In 1874 a German graduate student named Othmar Zeidler published the synthesis of dichloro-diphenyl-trichloroethane for his dissertation thesis. DDT was just another interesting compound whose synthesis further demonstrated that organic chemicals could be created from inorganic substances. (Prior to the 19th century, matter was thought to come in two forms termed organic and inorganic. It was believed that organic matter could only be created within a living organism.) Such small advances in chemistry, along with other scientific and technological developments would soon revolutionize pesticide manufacturing and usage.

While the earliest pesticides were crudely made from naturally occurring toxic substances, improved chemical techniques allowed for the refinement and mass production of those substances. The 20th century saw old familiar compounds like lead arsenate (prepared by reacting soluble lead salts with sodium arsenate), pyrethrin (typically refined from Tanacetum cinerariaefolium or T. coccineum) and the Bordeaux mixture (a lime and copper sulfate combination), become widely sold commercial products.  Pesticide usage steadily grew. In 1934 records indicate that 1.5 million pounds of rotenone (extracted from several genera of poisonous leguminous plants including Derris spp., Lonchocarpus spp., and Tephrosia spp.),10 million pounds of pyrethrum, 73 million pounds of sulfur, 80-90 million pounds of arsenicals, along with millions of gallons petroleum based oils and extractions (like mineral oil and naphthalene) were being used in the United States, (Rowe, 2003).

Although the pesticides sold in the first half of the 20th century were generally extracted from natural sources, this changed after 1939. In that year, Swiss chemist, Paul Muller, discovered that DDT made an excellent insecticide. DDT proved remarkably effective for the control of insect-borne diseases like malaria, and Muller was awarded the 1948 Nobel Prize for helping to save so many lives with this 'wonderful' pesticide. Its use on farms and in home gardens began in 1944, and soon millions of pounds were being applied around the world. US annual usage peaked at around 80 million pounds in 1959.

In that same year, the first DDT-resistant mosquitoes were detected in India. (There are now resistant populations world wide, including here in Canada.) In addition to becoming less effective, it was recognized that DDT, like other non-selective insecticides, was killing beneficial insects along with the targeted pest species. When natural enemies of insect pests are eliminated, secondary pest infestations occur along with larger primary pest outbreaks, a phenomenon called pest resurgence. Of course, the most publicized problem with DDT was that it appeared to be accumulating in fish-eating birds, dramatically reducing reproductive rates by causing eggshell thinning and embryo death.  With Rachel Carson's publication of Silent Spring, in 1962, a general alarm was sounded and the miracle of modern pesticides was called into question. "A major effort to reevaluate the role of pesticides in U.S. agriculture emerged; it culminated in the creation of the Environmental Protection Agency [EPA], a ban on DDT (and later other organochlorine insecticides) for all agricultural uses, and passage of legislation regulating the production and use of pesticides. Since 1971, many synthetic organic insecticides have been canceled or restricted because they posed health or environmental risks," (Committee on the Future Role of Pesticides in US Agriculture. 2000).

Despite concerns, the use of pesticides has expanded. In 2001, world pesticide usage exceeded 5.0 billion pounds, with the U.S. accounting for over a fifth of that. Home and garden pesticide use represented about 10% of total pesticide usage. Herbicides made up the largest portion, followed by insecticides and then fungicides. The most commonly used residential herbicides were: 2,4-D, Glyphosate, Pendimethalin, Mecoprop, and DCPA (Clorthal), while insecticides included: Diazinon, Carbaryl, and Malathion and the fungicides preferred were: Benomyl, and Captan. (Note that I have been using predominantly U.S. statistics because Canada only implemented reporting regulations in June of 2006.)

As a growing number of epidemiological investigations reveal associations with human disease and pesticide use, government agencies around the world, like our Pesticide Management Regulatory Agency (PMRA), have been tightening pesticide regulations.  For instance, based on recent reevaluations, use of racemic mecoprop, diazinon, and benomyl is being discontinued, while uses of malathion and carbaryl have been severely restricted. In addition to regulatory changes, there are many educational governmental initiatives aimed at reducing pesticide usage. Plant growers are being encouraged to implement Integrated Pest Management (IPM) systems. By understanding the life cycles of diseases, weeds and insects, farmers and home gardeners alike can develop pest management strategies that rely on natural controls rather than pesticides to maintain healthy gardens and crops.

We understand a great deal about the connections between cultivation practices and garden health. From careful preparation of soil and selection of plants, to proper pruning and watering, we can do much to eliminate garden problems. If our best efforts fail and pests become a real problem, and not just a nuisance, we may have to reach for a pesticide. At that time, we should always remember that pesticides, (be they from natural sources or synthesized), can pose risks to humans and to the environment and should be used with great care. 

Over the next months, I will describe a variety of environmentally-sound methods for addressing some common pest problems.

 

May toads nestle in your flower beds and help you tend your beauties in the spring.

 

Resources, References and  Interesting tidbits:

Interesting Tidbits

Arsenicals:

"Arsenate products with colorful names such as Paris green and London purple, were among the first materials used to control codling moth in Washington orchards. Paris green (copper aceto-arsenite) was used as a pigment in green paints, fabrics, and wallpaper, before being adopted as an insecticide. By the turn of the century, it was the leading arsenic-based insecticide in the country. London purple, a liquid waste product of the synthetic dye industry, contained a variable amount of a calcium-arsenic mixture. ...

Lead arsenate was first prepared as an insecticide in 1892 and was used in a gypsy moth eradication program in Massachusetts before being adopted in Washington. At first, growers made their own paste formulations. Its popularity as a control for codling moth increased after a commercial powder form became available in 1909." [Warner, 1996]

"An artist who recently produced his own oil paint with Paris Green obtained from a fireworks supplier suffered arsenic poisoning from vapors which emanated from the finished paint. Either impurities were the cause, or the molecule itself spontaneously degrades, creating a highly toxic arsine gas. This was Cezanne's favorite pigment, and it dominates many of his paintings. In his watercolors, thin washes have turned brown but thicker applications have remained bright green. The pigment was also used heavily by other artists of his era, such as Van Gogh. Cezanne developed severe diabetes, which is a symptom of chronic arsenic poisoning. Monet's blindness and Van Gogh's neurological disorders are likely directly related to their use of Emerald Green, as well as lead pigments, mercury-based Vermilion, and solvents such as turpentine." [Paris Green, Answers.com ]

Cryolite:

"Cryolite (Na3AlF6, sodium aluminum fluoride) is an uncommon mineral of very limited natural distribution. It is mostly identified with the once large deposit at Ivigtut on the west coast of Greenland, which ran out in 1987." [Cryolite - WIKI]

"As it happened, the parent company numbered among its processes at Natrona, Pa., the refining of natural cryolite for use by the aluminum industry. In a final grinding, a certain amount of fines remained, and as the operation was somewhat dusty, cryolite dust carried to parts of the plant where there was vegetation. Workers at Natrona empirically noted a remarkable lack of chewing insects on the foliage at the plant, and during this period had formed the habit of using these “waste”  fines from the final grinding as an insecticide in their home gardens. (Cryolite apparently was first used formally as an insecticide by S. Marcovitch and W. W. Stanley of the Tennessee Agricultural Experiment Station in 1929.)" ACS 1955 

Rotenone:

Rotenone (C23H22O6 is a colorless-to-red, odorless solid. In solution it is used as a broad-spectrum insecticide that works by inhibiting the transfer of electrons from Fe-S centers in Complex I to ubiquinone (see electron transfer chain). This prevents NADH from being converted into usable cellular energy (ATP). [Rotenone - Wiki]

Fertilizers:

In the early 20th century, the Haber-Bosch process made possible the efficient synthesis of ammonia from nitrogen and hydrogen. This process immediately created an important feedstock for German explosives during World War I and enabled a quantum leap in the world’s agricultural capacity, which was necessary to sustain the world’s growing population. [Haber-Bosch process - Wise Geek]

 

Resources, references and sources of interesting tidbits: