by Pat Kelley, BCE
Like Clark Kent changing into Superman, some insecticides begin as mildmannered chemicals that literally couldn’t hurt a flea. Where Superman would use a phone booth (What’s a phone booth?!?) to make his change, one particular group of insecticides changes into more powerful and deadly compounds within the cells of an insect’s body. This chemical alteration is called biotransformation and the pesticides that exhibit this change are called “pro-insecticides.”
Due in part to exploration into nerve gasses during WWII, approximately 90% of the insecticides on the market today attack and kill insects through their nervous system. To defend against these types of poisons, insects and people alike have protein-based defense mechanisms built into their cells that are designed to remove foreign substances. As an example, after a heavy night of drinking, human bodies detoxify from excessive amounts of alcohol with the help of an enzyme named Cytochrome P450. This enzyme binds up with alcohol and chemically changes it into water and other byproducts that are more easily passed through and out of our system. Hangovers and extreme thirst after binge drinking are due to this enzyme flushing out the alcohol as well as a majority of the water that is stored in our body tissue. We basically become dehydrated during this process and we feel bad or sick the next morning.
In the same way, when an insect comes in contact with foreign chemicals, cellular-level warriors such as Cytochrome P450 enzymes quickly get to work to convert the toxic chemicals into water molecules that can be flushed out of the insect’s system. While typical insecticides are designed to trick or overpower Cytochrome P450 enzymes in order to reach the nervous system of the insect, pro-insecticides embrace these enzymes. In the case of proinsecticides, instead of detoxifying these chemicals, the enzymes actually activate the chemicals. This converts them from relatively non-toxic compounds into deadly pesticides. A few examples of proinsecticides are thiocarbamate insecticides as well as the pesticides indoxacarb, sulfuramid, and chlorfenapyr. One big advantage of pro-insecticides is that their mode of action to kill insects is very different than most standard insecticides. Because of this, they make a great choice when one is looking to rotate pesticide products in order to reduce the likelihood that insect pests will develop resistance to any one type of insecticide. Although it’s not quite bug “kryptonite”, proinsecticides can really be a pest’s biggest weakness.