What Are Green Grubs?

Green Grubs

• Green June beetles overwinter in lawns and emerge in the spring. These pests prefer to lay their eggs in moist, fertile soil. Female green June beetles dig holes in the soil and lay up to 30 eggs. After the eggs hatch in 10 to 15 days, larvae feed throughout the night on grass, roots and organic matter. If winter comes before green June beetles mature into adults, grubs dig down into the soil to spend the winter.

Damage

• Grubs tunnel through the first 4 inches of topsoil. Their tunneling loosens soil and thatch. You may see small mounds throughout your lawn due to green grubs' tunneling habits. Mounds are generally 2 to 3 inches in diameter. Upon a closer examination, you may see openings in the tunnel. Water-stressed lawns easily die off from the damage, especially if grass is kept short. Furthermore, tunnels ruin the uniform texture of the lawn. Before applying a pesticide to the lawn, conduct a green grub test to verify that they are the cause of the damage.

Testing and Cultural Control

• Green grubs are not the only insects to make mounds. Mounds throughout the lawn may be caused by earthworms. To test your lawn, cut out a square foot piece of turf that is 2 to 3 inches thick. Examine the soil and grass blades for green grubs. Use both cultural and chemical treatment to treat green grubs. Employ cultural control methods to combat their damage by overseeding thin areas. Also, raise your mowing height to 3 inches to help grass blades recover from their damage.

Cultural Control

• Dilute a pesticide that contains carbaryl to the yard at a rate of 3 oz. per 1,000 square feet. Apply the pesticide sometime between late summer and early fall or from August through October. Withhold water after treatment, as the water in some locales may be too alkaline. Carbaryl loses its effectiveness when watered with water that has a high pH. Rake up dead green June beetle grubs when they die out over the lawn. Reapply the spray in the spring.