There are seven types of pesticides: insecticides kill insects, herbicides kill plants, rodenticides kill rodents, bactericides kill bacteria, fungicides kill fungi and larvicides kill larvae.
One of the three most common pesticides, the chemical dichlorophenoxyacetic acid, known to gardeners as 2,4-D was developed at Rothamsted Experimental Station in England and was in widespread use by the late 1940s. Some authors suggest it was part of a program to discover a product that would destroy food crops in Germany and Japan, or equally possible, to increase crop yields of the Allies by suppressing weeds.
2,4-D kills plants by causing the cells in the tissues that carry water and nutrients to divide and grow without stopping. We recognize plants affected by 2,4-D by their elongated, grossly twisted stems. Herbicides that act this way are called auxin-type herbicides.
It is difficult to state specifically when public concern was first raised about the presence and the amount of 2,4-D in our gardens and fields. An article available on line, “Agent Orange in Your Backyard” by Gina Solomon in the February 2012 edition of The Atlantic magazine, discussed concerns, now common, of 2,4-D (tracking it into the house, its presence on the feet of pets) and also listed common over-the-shelf products that list on the label, in very small print, 2,4-D mixed with other pesticides that can cause havoc in the garden and the compost pile. The author cited Bayer Advanced All in One Lawn Weed and Crabgrass killer (2,4-D, Dicamba and others); Ortho Weed B Gon Max (2,4-D, Dicamba, Quinclorac and others); and Sta-Green Weed and Feed (2,4-D, Dicamba and others). To know exactly what is in the products you use, Google: ‘list of ingredients in (name of product).’