If your grass is turning yellow and dying, there is an easy way to tell if grubs are the culprits. Walk out to your grass and slip your fingers under the blades. If the grass turf rolls up like a carpet, you have an infestation of grubs. Grubs survive by eating away at the roots of plants. This is why you can easily lift your turf like a rug. However, grubs can also be easily treated.
Grubs are the larva stages of beetles. Many of the scarab beetle family such as Japanese beetle or June bug are given a general classification of "white grubs." These grubs are C-shaped. They vary in size depending on the actual species. White grubs have six legs beneath their head and an abdomen that grows in size along the creature's body moving toward the tail. Grubs start life tiny insects and grow as they shed their skin.
Undesirable predators such as moles feed on grubs. However, eliminating grubs from your yard may not discourage these predators, since moles also feed on earthworms in a lawn. Grubs may also attract ground beetles, ants and predator wasps. There are no commercially available natural pesticides that incorporate ants, wasps or other forms of beetle.
Grub infestations will be worse in areas where beetles are attracted. For example, Japanese beetles may often be found near roses. Lawns near rose gardens may have higher concentrations of grubs from Japanese beetles than lawns planted elsewhere. One method of grub control is to eliminate the beetles before they can produce new grubs. Handpicking beetles off plants and trapping them with water and soap traps will help to keep down on grub populations.
Insecticides for grubs are most effective when grubs are in the topmost layers of soil. This is why you should not apply an insecticide for grubs in fall or winter. During these times of year, grubs burrow deep into the soil. Before applying an insecticide to kill grubs, water your lawn well. The water forces grubs to the surface of the soil where treatments are more effective. Late July through August when new grubs feed near the surface of soil is the best time to apply grub controls. These insecticides are not effective in May and June because grubs are older and more resistant. Newer insecticides that are applied in June may leave residues in the soil that will kill new grubs in July and August.
Control grubs with biological controls as well as insecticides. Biological controls involve introducing natural diseases or parasites into a grub's environment to kill grubs. The two most effective of these are bacterial milky disease and parasitic nematodes. A nematode is a microscopic roundworm that invades the body of a grub and steals the grub's nutrients. Nematodes may gradually cause a grub to decline in health until it dies. Tests with bacterial milky disease have shown them to be effective in killing grub populations. However, the spores must be nurtured for 2 to 3 years to reach effective levels.