The application of DDT as a pesticide result in the storage of the substance in the fats of an organism's body and thus remains toxic for several years. This may cause issues in animals and may ultimately reach all the other species in the food chain.
So, in order to make a less harmful pesticide, one would need the features, which would make the pesticide to only influence the pests, and would also want it to function more promptly. A pesticide is less harmful if it monitors what one wants to control and does not affect other organisms in the surrounding.
A less harmful pesticide would only monitor aphids, gypsy moths, or nuisance wasps, but would not kill honey bees, butterflies, praying mantis, or ladybugs. The pesticides, which would not remain in the environment are generally less harmful, in comparison to those that remain in the water, soil, or air for a longer duration.
