In the turf industry, a pest is a generic term given to weeds, insects and diseases, alike. For now, I’m going to make it simpler by terming pests as insect invaders.
Most lawn pests lay their eggs in the spring, giving their young most of the spring, all of the summer and into autumn, the chance to thrive on a host (your lawn) full of highly nutritious food to make them grow strong and lay their eggs in the next season so that the next generation can be spawned. The problem is that your lawn is the pests feeding ground and, in great numbers, they will decimate a lawn in a few days.
A simple test to initially identify a potential problem is to get a watering can full of water and mix in some washing detergent. Make sure it’s mixed in; and don’t put the washing detergent in first. YOU DO NOT WANT IT TO FROTH! Pour the soapy water over several sections of your lawn area with each area covering about one square metre. Make sure that each area gets a good drenching- about a litre per square metre. The mix will seep into the soil and acts as an irritant to just about every bug in the upper soil profile. Any bug in that area will quickly surface and can then be identified. If you have 10+ bugs of any description in that square metre area, you may have a problem that needs to be addressed immediately.
If you do find pests it is imperative that you take action as soon as possible, remember pests see your lawn as a breeding ground.
The attached PDF shows a chart of the most common pests (insects), the stage in life they are most aggressive towards a lawn, what signs to look for and what treatment can be used.