For managing annual white grub populations, when should insecticides be applied?

For managing annual white grub populations, when should insecticides be applied?

• A. When grubs are small and feeding in the upper 2 inches
• B. When grubs are large near the soil surface
• C. During winter when the ground is frozen
• D. During peak adult flight

Answer: (A)

The timing for applying insecticides to manage annual white grubs hinges on the grub’s size and where it is in the soil. Insecticides work best when grubs are still small and actively feeding near the surface, within the upper two inches of soil. At this stage they are actively eating turf roots and are more exposed to the treated soil or to systemic/soil-penetrating products, making the kill more effective. If you wait until grubs have grown larger near the surface, they’re harder to kill because larger instars have tougher bodies and are closer to pupation, reducing the insecticide’s effectiveness. Applying in winter when the ground is frozen won’t reach active grubs, and many products aren’t active or able to move through cold soil. Applying during peak adult flight targets the beetles adults, not the larvae that are causing root damage, so it won’t address the grub population present in the turf. So the best practice is to apply when grubs are small and feeding in the upper 2 inches of soil, typically in late summer to early fall in Kansas.

The timing for applying insecticides to manage annual white grubs hinges on the grub’s size and where it is in the soil. Insecticides work best when grubs are still small and actively feeding near the surface, within the upper two inches of soil. At this stage they are actively eating turf roots and are more exposed to the treated soil or to systemic/soil-penetrating products, making the kill more effective.

If you wait until grubs have grown larger near the surface, they’re harder to kill because larger instars have tougher bodies and are closer to pupation, reducing the insecticide’s effectiveness. Applying in winter when the ground is frozen won’t reach active grubs, and many products aren’t active or able to move through cold soil. Applying during peak adult flight targets the beetles adults, not the larvae that are causing root damage, so it won’t address the grub population present in the turf.

So the best practice is to apply when grubs are small and feeding in the upper 2 inches of soil, typically in late summer to early fall in Kansas.