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

Rick Orr is the creator of Iloveturf.com, Owner/Operator of APL Pest Control and a graduate from VA Tech in Agronomy (Turf Ecology).  

Since 1980, Rick worked in the green industry, mostly with golf courses, resorts and large communities. Rick worked as a Golf Course Superintendent of Fripp Island Resort, agronomist for Seaside, FL and the spray tech for Vinoy Golf Course. Rick has been certified as an arborist, landscape and irrigation contractor and adjunct professor for Environmental Horticulture (SPC) in Pinellas County.  

Home Pest Control came naturally. Entomology (bug science) was part of agronomy studies. Nearly every indoor pest problem starts outdoors. Crossing over to home pest control from lawn spraying was a natural process – the technology, methods and materials used for home pest control are modifications of the ones used for lawn spraying. 

The results of that work is a one of the top rated pest control companies in Pinellas County – APL Pest Control. APL Pest Control is a family owned business serving residential and commercial properties in Pinellas County, FL. 

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Speaking Engagements - Does it seem like you are only hearing one side of water restrictions, fertilizer bans, plant restrictions, and many other urban landscape hot topics? Rick Orr is available for speaking engagements for your HOA, Community or Professional Association or Garden Club about a variety of subjects. To contact Rick you can find him on FacebookTwitterLinkedIn and Instagram for booking information.