This is because the pheromones are a natural part of the organisms and the species cannot survive without pheromones. Furthermore, pheromones occur naturally and are non-toxic. As a result, these strategies avoid destructive pollution. Most importantly, pheromones are target specific, meaning they only eliminate the intended organisms with little or no ecological side effects. In comparison, pesticides are very general chemicals that harm anything that may come in contact with them, killing beneficial as well as harmful organisms.
Pesticides accumulate in the food chain, therefore affecting even more non-target organisms.
Some of the non-target organisms affected are natural enemies, such as predator insects of the harmful pests. Once an area is treated with a pesticide, the pest and its natural enemies are both most likely destroyed. Because pesticides have to constantly be reapplied, the pest might become resistant to the pesticide. However, the natural enemies of that particular habitat might not be resistant. If this is the case, the pest will return in even greater quantities than before.