Should I Treat My Lawn for Grub Worms?

Pest Description

• Grubs are the larval stage of numerous beetles, including May and June beetles, scarab beetles, Japanese beetles and masked chafer. All grubs are generally soft-bodied and dirty white in color with six sturdy legs and brown heads. When the turf is disturbed, the 1-inch-long pests lie on their sides in a C-shape.

Damage

• The adult beetles rarely damage lawns, but all larvae feed on roots and seriously affect the water and nutrient conducting ability of grass. Affected grass areas turn soft and spongy, pull up easily and gradually start to yellow and die. Damage creates irregular brown patches that get larger with time.

Preventative Strategies

• Prevention involves treating the grass with long term residual insecticides. Recommended insecticides include imidacloprid, clothianidin, thiamethoxam, halofenozide or chlorantraniliprole. All products target the young grubs in the grass and some also help to reduce adult beetles.

Curative Strategies

• All curative insecticides work best when applied to lawns in summer when grubs are very young and feeding mostly at soil surface. Check lawn regularly to establish the presence of grubs in grass before starting treatment. This also helps to target treatment on affected spots. Treating lawns in spring is not as effective as during the summer because the grubs are larger in size and harder to control. . Recommended curative insecticide includes trichlorfon.