Grub control products are currently being displayed in the center aisles of retail department and discount stores and are advertised on the radio as providing season-long grub control when applied in early May. What are the facts behind this recommendation?
While certain grub control products do have a very long residual in the soil, they should not be applied to lawns by both homeowners and professionals until later in the summer and here are 4 reasons why not:
1. The goal of white grub insecticides is to prevent turf damage, not eradicate grubs. Grub damage in the spring is very minimal and only seen in the driest of years. Since there is a limited chance of significant grub damage, why apply?
2. Grubs found in the turfgrass right now are the stage that passed the winter. These feed very little and are extremely difficult to kill. Insecticides applied now will not be very effective.
3. Even if you could control grubs now, it will have no effect on the population of grubs come next August when the really damaging generation hatches.
4. Insecticides applied now will biodegrade over time and may not remain in the soil at high enough concentrations to be effective in August when we really need them. (Certainly, they will be more effective if applied closer to the egg hatch date in early August).
For these and other reasons, you are better off waiting until July through mid-August to apply white grub insecticides and then only apply if your lawn has experienced perennial damage from grubs or if you find more than five grubs per square foot.