Can you explain in more detail what you mean by bad infestation? Are you seeing larvae or adults? Are you seeing damage to your lawn?
If you are talking about crane fly larvae, I would need to know how many you find per square foot of soil. One easy way to determine this is to use a 6" square point shovel and dig a hole one shovel width wide on all sides and about 4" deep. Dig through the sod and count the larvae. Multiply the number of larvae you find by 4 and that gives you the amount of crane fly larvae per square foot.
It is important to note that healthy lawns can tolerate between 25 and 50 larvae per square foot without appreciable damage. The presence of crane fly larvae in and of itself it not a problem. And the presence of adults is not an issue since there is no relation between adult population and larvae that survive because of bird and other predation of the larvae.
The real question is whether you are seeing damage to your lawn. If so, you have another consideration: the crane fly larvae are near the end of their feeding life cycle. If you have unacceptable damage, one option is to apply an insecticide. There are many choices, but some of them only work when applied in September when the larvae are tiny. So, it is important to choose the correct insecticide if you want to apply one. The other option is to simply over seed your lawn. Crane fly damage rarely destroys the entire lawn, but generally thins some selective areas. And high populations in one year do not guarantee high populations in the next year.
One easy way to reduce the amount of larvae is to not water your lawn after Labor Day. September is when the adults lay their eggs and the eggs need water to survive.
If you can give me some more information about what you are seeing, I can give you some specific advice on whether you might want to consider applying an insecticide.