White Grub Damage Looks Like Water Stress Even When Wet and The Turf Is Not Rooted in the Soil


By Rick Orr 04/15/2020
St Augustine grass lawn damaged by grubs
St Augustine lawn damaged by grubs

Grub Damage Mimics Water Stress

White Grub damage mimics water stress and water stress mimics grub damage – the two are hard to tell apart. The best test is to half kick, half scuff your shoe across the grass  -  like you’re trying to move a throw rug - if it doesn’t move – fix the irrigation. If it does move like a throw rug on a terrazzo floor – you have grubs. If you look under the sod, you may find the white "C" shaped fat little grubs laying on the soil surface.

Grub laying on soil surface next to leaf
White grub found just below damaged grass that was easily lifted off the soil

Simple Test for Grubs

Grubs have their favorite spots in the lawn. This causes random spots in the lawn that appear to be water-stressed. If grubs are the cause,  when you tug at the water-stressed sod, it should lift easily from the soil. Grubs may or may or may not be present as they burrow into the soil to avoid heat and drought.

Grub Biology

Grubs feed on grass roots from late spring to fall. For winter, the grubs burrow deeper into the soil and emerge in spring as beetles. The beetles lay eggs that hatch into grubs in the late spring and feed on grass roots all summer and into the fall.

Note: finding one or two grubs in a lawn does not indicate your lawn has a grub problem. A few grubs are beneficial – their burrowing helps aerate and excrements fertilize the soil. It is when they overpopulate an area that causes lethal damage. The treatments I use do not eradicate grubs – they maintain population levels below damaging levels.


If you had grubs last year, you'll probably have them every year and most likely in the same spot. Apply a granular insecticide labeled for grubs in the evening and water in the application with 0.25 inches of water. Be sure to apply the insecticide a 2 – 3 feet beyond the damage.

The prime time to treat for grubs in Pinellas County is June through August - while grubs are small and easy to kill – long before the damage appears. I start treating for grubs in mid-June through August with synthetic botanical insecticide for sub-surface insects. The treatments are broad-spectrum and reduce mole crickets, weevils, and ants in the lawn and landscape.

Post Damage Recovery

If you have grub damage apply a good insecticide and turn on the water. The grub damaged turf is like fresh sod and needs to be watered daily to recover.

Rick Orr Owner-Operator APL Pest Control/Creator of ILOVETURF.COM
APL Pest Control

Since 1995, Rick Orr has worked in Pinellas County providing turf management and pest control. Rick Orr is a graduate of VA Tech in Agronomy (Turf Ecology) and the creator of Iloveturf.com.

Since graduating from VA Tech in 1979, Rick worked in the green industry, mostly with golf courses, resorts, and large communities. Rick has obtained certifications in arboriculture, landscape contractor, and irrigation contractor, and taught Environmental Horticulture at St Petersburg College. 

Currently, Rick is the owner and operator of APL Pest Control. APL Pest Control provides lawn care and pest control for all of Pinellas County.

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