Insect
Resistance

Pests are always one step ahead of the chemical insecticides used against them  

 

Modern agricultural practices involving the extensive use of chemical pesticides and genetically modified (GM) crops create an environment with less biological and genetic variation – perfect for the development of insecticide resistance.

The problem is that chemical insecticides counter the fundamental forces of nature. These toxic chemicals are designed to kill insects. They wipe out pests and beneficial insects alike, resulting in a lack of biological competition, including fewer of the pests’ natural predators. Presented with an endless buffet in the fields of modern monocropping, pests evolve to become less responsive to the insecticides used to control them. Scientists estimate that around the world more than 500 pests are able to resist over 300 different insecticides. For growers and agrochemical companies, it is a constant race to stay ahead of the insects.

Diamondback moths mating

To understand why insects do NOT develop resistance to pheromones, we must turn to Darwin

Most insects eventually develop resistance to chemicals used to control them. This is the case for the fall armyworm eating its way through maize around the world. It is also the case for the Anopheles mosquito carrying malaria and even for head lice rampant amongst school children in many western countries. Resistance is in fact a perfect example of Darwin’s principle of natural selection. As random DNA mutations arise spontaneously in all living things, one such mutation may just make an insect a little more likely to survive long enough to reproduce, in turn passing on this trait to its offspring – and insecticide resistance is born. Pheromones, on the other hand, are used by insects to find a mate (mating disruption). Thus, it would doom the entire species to extinction to develop resistance to mating disruption. Since mating disruption does not kill insects, it is unlikely that resistance will occur, especially because mating disruption typically is part of a broader approach for integrated pest management (IPM) that uses several, mutually supporting practices to control pests.

 

A case in point: the Fall Armyworm

Since 2016, it has spread from the Americas to all but the coldest regions of the world, constituting a serious threat to food security. The Fall Armyworm devours many different crops, but its favourite remains corn, the staple crop of more than 300 million Africans. In the past, the Fall Armyworm would be controlled using chemical pesticides, but the pest has developed resistance to most insecticides. The same is true of GM seeds such as corn or cotton expressing the Bt-toxin. The only way forward, according to the Food and Agriculture Organisation, is to embrace Integrated Pest Management.