Recently I had a conversation with a scientist friend who told me how biologists use information about animal life cycles to accomplish diametrically opposite objectives – in some cases to purge populations, and in others to conserve them. The secret: determining in which stage of its life cycle is the animal most vulnerable. And it’s at these points of vulnerability that either the worst or the best is the easiest to accomplish. It is when the animals are at greatest risk that it takes the least effort to destroy them, or conversely, to protect them. He gave me two examples to illustrate his point.
The Bertha armyworm
The Bertha armyworm is a significant insect pest of canola in Manitoba, Saskatchewan, Alberta and the interior of British Columbia. Like many insects, it goes through a four stage life cycle – egg, larva, pupa and finally, the adult moth stage. However, their vulnerability is greatest at the larval stage. As eggs, they are not susceptible to pesticides; as pupae, they are buried in the ground and therefore well protected; as adults, they are widely dispersed and therefore difficult to control. Because scientists know that the insect’s defences are the weakest when at the larval stage, substantial and successful control efforts are targeted at this point in the life cycle. Continue reading