In the US, about 62% of planted acreage is treated at least annually with some kind of pesticide (93% of row crops are). This leaves about 38% untreated, and that is largely forage crop acreage (<10% of forage crop acreage gets treated).
Total pesticide use in US agriculture increased greatly from the mid-1960's through the mid-1980's, owing largely to the development of a variety of new pesticide compounds. There was a dip in pesticide use from 1982 - 1987, with the main reasons for that decline including:
land idled from production to decrease surpluses
introduction of newer products that are applied at a lower rate per acre
implementation of IPM systems, particularly for insects
Use increased again into the '90's, in part because land formerly idled from porduction was returned to cropping. Over the period 1964 - 2004, 1997 saw the highest use of pesticides in terms of millions of pounds of active ingredients applied to major crops in the US. Some of the newer pesticides are applied at lower rates -- and, as we'll see, use of genetically modified crops may also have effects on pesticide use (both increasing it and decreasing it, depending on the crop and situation).
See this USDA site for information on pesticide use in US agriculture by year -- and see also links for more information in the introduction to this pesticide unit.
We can break these trends in US agricultural use of pesticides into types of pesticides used:
Increases in herbicide use led the increases in pesticide use in agriculture for many years. For example, by 1985, 90% of corn and soybean acreage was being treated with herbicides, while in 1970 only 40% of the acreage was treated. Overall, herbicides were used on over half of us cropland in 1991. As a percentage of total pesticides applied, herbicides rose from 33% in 1966 to 70% in 1986, and herbicides still dominate in terms of pounds of active ingredients applied.
Why were there such big increases in herbicide use?
Increases were related in part to aggressive research on and development of new herbicides, and also in part to expanded use of no-till or "conservation till" practices, which were developed, in part, to control soil erosion. (We'll talk about conservation till later, but for now, it is a technique which minimizes turning of the soil, as by plowing and cultivating. Because cultivation isn't generally used to control weeds in conservation till systems, herbicide use often increases . This is yet another example of a solution to one problem (soil erosion in this case) resulting in new problems (increased use of herbicides).
A final factor contributing to increased herbicide use in US agriculture has been the rapid adoption by farmers of crops that are genetically engineered to tolerate herbicides.
As of 1997, insecticides accounted for about 10 % of the pesticide pounds of active ingredients used in US agriculture. Use in some crops is much heavier than others; corn and cotton tend to be relatively heavily treated with insecticides, as are many fruits. Some crops are treated as much as 20x/year, such as apples.
Between 1966 and the late 1980's, insecticide use declined, with another decline beginning in the late 1990's; use has been fairly stable or declining slightly since then. The declines are largely because of the implementation of IPM programs in insect control ("Integrated Pest Management"), because of introduction of new pyrethroid insecticides, which are applied at about 1/10 the rate of traditional insecticides, and because of the increased acreage planted to plants (notably corn and cotton, in terms of acreage, that is genetically engineered to produce pesticides. (We'll discuss IPM systems and the use of genetically-engineered crops when we focus on sustainable or alternative agricultural approaches.
Fungicides account for the smallest share of total pesticide used, and they are primarily used as seed treatments and to protect fruits and vegetables during production and after harvest.
"Other" pesticides showed the largest increase in terms of pounds of active ingrdients applied between 1964 and 1997. These include soil sterilants (including methyl bromide, which we'll say more about when we discuss depletion of stratospheric ozone) which are used to control parasitic nematodes and other soil-inhabiting pests and pathogens, and various growth regulators, desiccants, and harvest aids. the latter affect the branching stucture of plants, control times of ripening or maturity, alter other plant functions to improve quality or yield, and aid mechanical harvest. One example is sulfuric acid, which is often applied at several hundred pounds per acre to kill potato vines to facilitate harvest.
Page maintained by Patricia Muir at Oregon State University. Last updated Oct. 23, 2012
The next section (">>" at the bottom of the page) looks at global trends in pesticide use.