We’re going to talk a bit more about pesticides in this tip to delve a bit deeper from a previous tip on pesticide classifications in Tip #155.
When it comes to pesticides, there are many different types of pesticides and ways to classify them. For example contact pesticides like insecticidal soap and horticultural oils must come in contact with the targeted pest to work effectively. Residual pesticides cling to the surface of a plant and remain active for a certain period of time before being broken down and losing their effectiveness. It is also important to remind readers that pesticides don’t always refer to chemicals and can include physical things like sticky traps, and mouse traps.
This week, we’ll be discussing systemic pesticides which are externally applied and then taken up inside the plant. Typically, systemic pesticides are taken up through the root system, though they can also be applied to the seeds, soil, and leaves. When it comes to food crops, the main systemic pesticides that are used are members of the neonicotinoid groups of chemicals, which are chemically similar to nicotine. These chemicals can remain active for months, or even years after application.
With systemic pesticides, another risk factor is the inability to wash or peel them off like other contact pesticides.
With plants, systemic pesticides typically refer to a chemical that gets taken up and permeates every part of the plant. When an insect then decides to feed on the plant, they are killed off by the pesticide.
As new research continues to find, these groups of chemicals seem to be one of the leading causes of colony collapse disorder that has killed millions of bees across Canada and North America. Systemic pesticides like neonicotinoids are toxic in both large and small doses. One common criticism of these chemicals is that very little is taken up by the plant, and the rest can remain in the soil or run off into the water system.
For more information on systemic pesticides, you can visit The Task Force on Systemic Pesticides for links to published, peer-reviewed studies. http://www.tfsp.info/worldwide-integrated-assessment/
Cover Image by Chafer Machinery, used under its Creative Commons license.