When should you
apply grub control?
Enter your ZIP code. We’ll tell you the best time to apply preventive grub control — based on real weather station data and Growing Degree Days.
Built on NOAA GHCN-Daily observations covering 33,000+ US ZIP codes, recomputed daily.
Data details
What to buy for this result
Some links are sponsored. We may earn a commission, but your ZIP result determines which product type we show.
Preventive grub control
Chlorantraniliprole
Scotts GrubEx
Best fit: You want to stop this season's grub damage before it starts.
Helps you avoid paying for rescue treatment later when timing still favors prevention.
Must be applied before grubs are active; needs watering in
Curative grub treatment
Trichlorfon
Bayer Dylox 6.2
Best fit: Active grubs are already feeding and turf is lifting or thinning.
Helps you avoid buying a preventive product after the useful window has likely passed.
Only works on active grubs; short residual
How GDD Predicts Grub Activity
Growing Degree Days (GDD) track accumulated warmth in your soil since January 1. When the average daily temperature exceeds 50°F, the difference is added to your running total. Japanese beetles and other scarab beetles emerge to lay eggs when GDD reaches roughly 1,000–1,300. Preventive grub control products need to be in the soil before those eggs hatch — that’s the window this tracker identifies.
Why Grub Control Timing Matters
Preventive grub products like chlorantraniliprole (GrubEx) work by creating a treated zone in the soil that kills grubs as they hatch and begin feeding on roots. Apply too early and the product may degrade before peak egg-laying. Apply too late and grubs are already established — you’ll need a more expensive curative product. GDD tracking ties your application to actual soil temperature rather than calendar dates, which vary from year to year.
This tracker pulls daily temperature observations from your nearest NOAA weather station and calculates GDD and estimated soil temperature for over 33,000 US ZIP codes.
Common grub control questions
When should I apply grub control?
Apply preventive grub control before newly hatched grubs begin feeding on roots. This tracker treats roughly 1,000–1,300 GDD (base 50°F from January 1) as the apply-now window — enter your ZIP code for your local status.
When should I apply GrubEx?
GrubEx uses chlorantraniliprole, a preventive active ingredient that needs time to move into the root zone. Apply it as your local GDD approaches the 1,000–1,300 range, before beetle eggs hatch, and water it in as the label directs.
When do grub eggs hatch?
Japanese beetles, masked chafers, and other scarab beetles lay eggs in early to midsummer, and eggs can hatch roughly 10 days after laying when soil moisture is favorable. Local heat accumulation shifts the exact timing from year to year.
Is it too late for preventive grub control if my lawn is already damaged?
Usually, yes. Visible damage means grubs are already feeding, so a curative product like trichlorfon (Dylox) is the better match — but confirm live grubs first by lifting turf near the damage edge, since drought and disease can look similar.
How many grubs per square foot justify treatment?
Healthy turf tolerates a few grubs per square foot. About 10 or more grubs per square foot, roots eaten back, or turf that lifts like loose carpet are stronger reasons to treat and to plan preventive control for the next season.
Guides by State
Timing varies across the country. Find your state for local timing windows.