Comprehensive Grub Management: Cultural Practices, Rescue Treatments, and Preventive Control

Comprehensive Grub Management: Cultural Practices, Rescue Treatments, and Preventive Control

White grubs (Japanese beetle and masked chafer larvae) feed on roots from late August to mid-October. Damage appears as brown, loose turf that lifts like carpet.

Cultural Practices to Reduce Damage

• Withhold irrigation in June–July to discourage beetle egg-laying.
• Water frequently in late August–September if grub feeding starts.
• Apply nitrogen in October–December only. Spring/summer nitrogen reduces root growth and increases grub damage.
• Raise mowing height to 3–3.5 inches in summer to discourage egg-laying and improve rooting.
• Consider tall fescue for renovation—it regrows roots fast enough to outpace grub feeding.

Rescue Treatment (Late August–October)

If active damage is seen, apply trichlorfon (Dylox / Bayer Advanced 24-Hour Grub Control). Water in immediately with ½ inch irrigation. Granular forms are more convenient.

Preventive Treatments (Apply June–July)

• Merit (imidacloprid) / Bayer Advanced Season-Long: Apply mid-June to mid-July. Disrupts insect nerves selectively.
• Mach 2 (halofenozide) / Scotts GrubEx: Apply mid-June to mid-August. Mimics molting hormone. Not effective after grubs are large.

Both persist for months; water in after application. Follow label rates exactly.

Renovation

Small dead patches fill in naturally in spring. For severe damage, remove dead turf, level with topsoil/potting mix, and reseed or sod with Kentucky bluegrass.

Biological Controls

Milky spore and beneficial nematodes have shown unreliable results in university tests.

Monitor annually; grubs often return to previously damaged areas.