Encourage Deep Grass Roots
Most lawns in America grow on compacted soil which has no air in it. Because grass roots can not penetrate deeply, lawns growing on compacted soil are always more vulnerable to visible grub damage. In aerated soil grass roots grow down 6 to 12 inches depending on the variety of grass. Any grubs feeding on them down there, are spread over a much larger area in the soil and their damage is less discernible over the season.
To effectively introduce air into the soil under your turf use either a hand or rented power core aerating tool. Their hollow tines pull plugs up or cores of soil and deposit them on the top of the lawn for the rain to dissolve. Lots of small holes remain that allow air to penetrate the soil down several inches. Do this in the spring or fall for 2 or 3 years to promote deep grass roots.
Attract Grub Predators To The Yard
Beneficial insects, spiders, and ants kill huge numbers of eggs, grubs and beetles and normally keep their population in balance in residential yards. Encourage the natural predators of grubs to stay in your yard by providing them with a tempting variety of their favorite plant sources of pollen and nectar such as the plants in Border Patrolä wildflower seed mix. Topdress and aerate turf to build rich soil that will support the soil dwellers that eat pest eggs. Avoid using broad-spectrum insecticides that indiscriminately kill both grubs and beetles and beneficial insects such as spined soldier bugs, ground beetles, wheel bugs, and the larvae of tachinid flies, which attack white grubs.
Invite Predator Birds
Next to beneficial insects, songbirds consume the most pest insects in your yard. Grackles, meadowlarks, crows, catbirds, cardinals, blackbirds, robins, and starlings eat lots of grubs. starlings, robins, catbirds, and cardinals also eat adult beetles. Encourage them to set up housekeeping in or near your yard and prey on grubs by offering them food, water and shelter.
· Provide seed in bird feeders and suet blocks for them year round. Reduce the amounts in the summer.
· Set up 1 or 2 bird baths for a source of fresh water. Consider acquiring an automatic self filling bird bath or a bird bath heater so that water is available year round.
· Some birds nest in bird houses if they are the correct size and height. Hang several on your property to attract summer tenants.
To learn all about these steps see the file Attracting Birds In the Home Landscape
Mow The Lawn Properly
Because adult beetles prefer to lay their eggs in short grass, cut your grass tall--a minimum of 2 inches high. This will prompt them to lay eggs elsewhere, effectively reducing the number of grubs and home-grown beetles you will have next year. Mowing tall benefits most turf grasses by boosting their ability to grow strong root systems, shade the soil and increase their energy production.
For more information see the file on Mowing Lawns
Manage Lawn Watering
Homeowners can influence the severity of grub problems somewhat by modifying their lawn watering practices in the summer. In the spring and fall, moist soil promotes microbial activity in the soil which means more beneficial organisms will be going after eggs and grubs. However, in the summer moist conditions promote the hatching of the eggs that are newly laid by the beetles. Therefore, in the summer water the lawn infrequently to deprive those eggs of continuous moisture.
For more information see the file on Watering Lawns
Avoid Attracting Adult Beetles
Use No Japanese Beetle Traps. Because their pheromone lures are so effective, Japanese beetle bag traps draw these beetles into your yard from as far away as 500 yards. In typical yards they actually attract more beetles than normally already reside on the property. Furthermore, all the beetles attracted by the lures do not fall into the trap, so you are effectively increasing your Japanese beetle population rather than controlling it. If a neighbor down the street hangs a trap in his yard you are likely to benefit as it draws Japanese beetles away from your yard. In the case of these beetles and the many other kinds that have grub larvae, the best bet is to knock them off plant foliage into a jar of soapy water when you spot them. This prevents them from laying eggs and hatching more grubs.