Organic and Chemical Grub Control Before Laying Sod

Managing Grubs in Colorado Lawns

Grubs—the larvae of beetles like June bugs and masked chafers—feed on grass roots, causing dead patches. In Littleton's climate (Zone 5-6), they overwinter in soil and emerge in spring.

Assess Before Treating

Cut several 1-square-foot sod sections 4–5 inches deep. If you find 5+ grubs per square foot, treatment is warranted. Random preventive spraying can lead to pesticide resistance.

Control Options

Chemical (apply at correct timing)

• Preventive: Merit (imidacloprid) in early–mid July for masked chafers; late May for billbugs/June bugs.
• Curative: Dylox (trichlorfon), Sevin (carbaryl), or Oftanol in spring/fall when soil temps reach 65°F.

Organic (can be used anytime)

• Milky spore (Bacillus popilliae): Long-term control, especially for Japanese beetles. Takes several seasons to establish.
• Beneficial nematodes: Apply mid-summer when grubs are active. Water in immediately.