Core aerifying, power raking and vertical mowing are mechanical processes that help break down some of the bumps in the lawn caused by earthworns.  Use of a heavy roller is not recommended. While rolling may remove some roughness, it also damages the turf by compacting the soil. Vertical mowing can help reduce the lumpiness and also the amount of food available for night crawler development. Vertical mowing is best done in late summer, mid-August through September. You can also power rake in spring once the ground is firm underfoot and before hot weather sets in. If you power rake in spring, apply a pre-emergent herbicide to prevent annual weeds from sprouting. Do not do vertical mowing in hot weather as it causes stress to the lawn. The best time to aerate is between late August and early October, depending on how far north you live. Spring or summer aerification can also be successful, especially when followed with regular, frequent watering. In spring, wait until you’ve mowed the lawn twice before aerifying. Then, unless you are reseeding the lawn, follow up with an application of pre-emergence herbicide after aerifying to help prevent annual weeds from sprouting.   Worms will continue to live  and poop so the soil will become uneven again over time.