Apply Insecticides Now to Kill Baby Grubs
Mid-June in the Transition Zone is the right time to kill the newest batch of grubs that feed on grass roots. There at nearly a dozen different species, but the dominant beetles that make grubs in STL are the chafers and the Japanese beetles. The B-52 sized June bug is less common, but when you come across a June bug grub, it’s freaky huge! You’ll scream like a sissy. If you’re unsure what a grub worm looks like, just Google it. [Are you shittin’ me? Don’t know what one looks like? Oh wait, I forgot that most millennials spent all their time in the basement playing video games!]
Eggs hatch and the larvae will eat the roots of turf. Egg hatch in STL is usually complete for all the species in early to mid-August. Grubworms go through a series of instar stages (molts) getting larger with each molt. Insecticides applied right now do a better job of killing the little babies while they’re small. We apply our systemic insecticides in mid-June so that the turfgrass has plenty of time to absorb and translocate the insecticide throughout the plant. Grub bites root—grub gets upset tummy—grub dies! Contact insecticides area applied in mid-August—because they don’t need to be taken up by the turf roots. Mr. Grub just digs and eats—insecticide washes over the poor baby—grub baby dies!
I will tell you now that the systemic products are more effective than the contact products for killing grubs. In dry years when the grubs are deeper in the soil, the contact products can be diluted in soil profile, and thus, less effective overall. They work great when the grubs are closer to the soil surface. On the other hand, contact products also kill fleas, ticks, spiders, crane flies, crickets, and a host of other bugs.
Grub damage tends to be patchy. Even when grubs are heavy in area, there will be individual clumps of surviving fescue plants—think “hair plugs for men!” This picture below captures the essence of a fescue lawn with grub damage. Note the relatively large patch of mostly dead grass. But note that there are several hundred individual clumps of grass (mostly fescue) that have survived! Some grasses contain an “endophyte” fungus that lives in the roots of infected plants. Grubs don’t like the alkaloids (natural insecticide) that the endophyte produces. Therefore we get this type of response–very clumpy. Kinda like “hair plugs for men!” Grubs don’t destroy 100% of the turf in the patches they infest.
Healthy, irrigated turf in STL can usually handle 10 or so grubs per sq ft, but crappy turf can’t. Weak turf might only tolerate 3 to 5 grubs/sq ft. When grub populations are extreme you can literally pick up turf like a throw carpet! I’ve seen this only once in my career, and the grubs were massive June bug grubs!
Below are photos of the 4 most dominant products sold for grub control. Be careful to use the right dose for grubs! While the bag may state, “Treats up to 12,500 sq ft” that’s for the surface-feeding insects. I’ll discuss their active ingredients, pros and cons, and cost from my local Home Depot (Lowe’s sucks, by the way).
Spectracide Triazicide Insect Killer: Contact Insecticide (cyhalothrin). Apply early to mid-August for grubs, but anytime for fleas and ticks. A 20 lb bag costs $13 and treats 16,600 sq ft. $0.78 per 1,000 sq ft.
Roundup Bug Destroyer: Systemic Insecticide plus Contact Insecticide (chlorantraniliprole plus bifenthrin). Apply early to mid-June. A 10 lb bag costs $17 and treats 2,500 sq ft. $6.80 per 1,000 sq ft.
Scott’s Grub Ex: Systemic Insecticide (chlorantraniliprole). Apply early to mid-June. A 14.5 lb bag costs $21 and treats 5,000 sq ft. $4.20 per 1,000 sq ft.
Bio Advanced Grub Killer Plus: Contact Insecticide (trichlorfon). Apply to mid-August. A 10 lb bag costs $19 and treats 5,000 sq ft. $3.80 per 1,00 sq ft.
Ortho Bug Be Gone: picture not shown. Bifenthrin contact insecticide. Special sale–10 lb bag for only $7.00. Treats 2,500 sq ft. $2.80 per 1,000 sq ft.
Professional Blends on Fertilizer Granules: Many professional LCO’s use non-nitrogen fertilizers with systemic insecticides (typically imidacloprid or acelepryn) at the recommended application time
If I were hosting a garden party, I’d purchase Triazicide and apply it a week ahead of time, to cleanse the area of surface pests. But for grubs, I recommend the systemic insecticides.
No get off your arse and apply your insecticide now!