I'm pretty sure because, chemicals and pesticides can easily make insects more immune. So therefore the average pesticides will no longer work on them but also some may not be affected by the solutions.
There would be fewer species of insects and fewer insects in general in the yard.
This is as the primary purpose of chemical pesticides is to control insects. To control insects refers to reducing the amount of insects. Therefore, it would ensure fewer amount of species of insects in the yard as well as ensuring that there are fewer insects in general in the yard.
For chemical reactions where the free energy of the reactants is much greater than the free energy of the products (DGo' < 0), the reaction proceeds spontaneously and the net result is a large ratio of product to reactant (large Keq).
