Grub control is a vital element of THE Turf Plan®, or any decent lawn program, for that matter. You simply MUST treat for grubs, because the root eating insects can cause significant turf injury in a very short period of time. Too many of you neglect this critical application!Injury to turfgrass occurs when the grubs (larvae of beetles) feed on grass roots, resulting in areas that turn yellow, then brown. Foraging animals, like raccoons, skunks and birds can further damage turf that’s heavily infested with grubs. Note the list in the prior sentence DIDN’T include moles! If you have moles, it doesn’t mean you have grubs. Earthworms are the primary staple of Mr. Mole’s diet…but they’ll eat any critter they happen upon, including grubs. Another important benefit of using insecticides on your turf is that they also provide effective control of other problem insects, such as billbugs, cutworms, chinchbugs and sod webworms.
There are two very effective insecticide products for the treatment of grubs, with different timings (and modes of action). The first option is a systemic product called imidacloprid, with a trade name of Merit® and others. “Systemic” means that after the product is taken up by plant roots, it will be spread throughout the plant, and thus, insects eating on the roots or leaves can be controlled. This product is Step 3 for both the GOLD and PLATINUM plans for cool season turf. Merit has enough residual activity that we time it before the grubs lay eggs in the summer. For the GOLD and PLATINUM plans we recommend the Merit® on a 0-0-7 fertilizer granule, because we don’t like nitrogen on the turf in June, and providing the lawn with a little potassium in the summer imparts some “stress tolerance.” This product needs to be applied to turf in mid-June here in St. Louis–and a 50 lb bag will cover 12.5M (12,500 sq ft of turf). Be sure to water the yard the day after application, if a good rainfall doesn’t occur.
But, for zoysiagrass, it is Step 2 for the WARM SEASON PLAN. The warm season formulation of Merit has a high nitrogen content because zoysiagrass needs nitrogen in June. A 50 lb bag covers 12,500 sq ft.
The second product we offer for grub control is Dylox® (active ingredient trichlorfon), which is another systemic product, but it’s timed for mid-August in St. Louis. This product is very fast acting and we recommend it for lawns in the PLATINUM PLAN as a second shot, or insurance against grubs. It’s Step 5 for the PLATINUM PLAN. In addition to its systemic activity, Dylox also has contact activity, which means that the grubs will die if they’ve come into contact directly with the insecticide, even without taking a bite of the turfgrass. A 30 lb bag will treat 10M (10,000 sq ft). To enhance the effectiveness of Dylox, we recommend that you time the application the day after a heavy rain or irrigation event. The water in the soil profile forces the grubs to move closer to the soil surface for oxygen. As long as there is not standing water on the soil surface, apply the insecticide. Follow that with an irrigation to water it in. The follow-up irrigation will effectively dissolve the active ingredient, and literally “wash it over” the grubs.
There’s another huge benefit of applying insecticides to your turf…you’ll control other problem critters, like chiggers, roaches, crickets and spiders! Lions and tigers and bears, oh my!
If you’re signed up for our newsletters you’ll get our email blasts that provide you with timely “do it now” information, to help you achieve maximum grub control. For example, if we’re having a summer that’s either really cool and dry, or exceptionally hot, it will affect the life cycle of the grubs, especially the egg hatch, and that will affect the “perfect timing” of the insecticide to achieve maximum grub control.
Where Do Grubs Come From
There are four significant families of beetles that cause landscape damage; May beetles, June bugs, chafers, and Japanese beetles (this horticultural trivia is useful at Happy Hour, when you’re trying to impress the hottest mom!). These are all the adult version of the white grub that loves to destroy our turfgrass. Most everyone knows what a June bug is…kinda like a milk dud with six legs…but, their smaller cousins, a host of “chafers”, are actually more numerous as grubs. Chafers are about half to two-thirds the size of June bugs, and they’re “bronzy” or copper-colored, compared to the classic dark brown color of the May or June beetle. And then, there’s the Japanese beetle…a smidge smaller than the chafer, but of all the species that make grubs, this one is by far the most damaging to landscapes in the adult stage. As most gardeners know, Japanese beetles can strip a garden clean in just a week or two, and they definitely have their favorite plants. Adult Japanese beetles are actually quite showy, with a metallic greenish-purple sheen. The giant of them all, though, is the “green June bug”; a huge showy, shiny metallic beetle…like a Japanese beetle on steroids. They’re enormous!
When you’re entertaining in the evening on the patio in the late spring and early summer, the chafers and June bugs are the species that are drawn to light. These are the dudes that scare the heck out of the ladies when they fly about. Ladies really freak for some reason, because they must think the beetles are going to bite them (which usually causes a predictable over-reaction…all that screaming and running…both hands flailing away…and if you’re lucky, some really funny prancing!). Indeed, the flying adult beetle does look big and scary, but there’s no need to worry, because these beetles aren’t going to bite. For sure, more harm comes from running around in the dark! The adult beetles are actually out trolling for the opposite sex, for the purpose of mating and laying eggs. After mating the female beetle commences her egg-laying over a span of 30 to 45 days, and they must eat to keep their energy up. And of course, they eat PLANTS! Night lighting will actually draw more of the chafers, May and June beetle adults to your garden. The more beetles you attract, the worse your grub problem can be. Go ahead and leave the lights on, but be sure to use an insecticide to control the subsequent grubs that will result from all the adult mating. By the way, the Japanese beetle is a day-flier, not a night-flier.
We’ve discussed the optimum timing for protecting your TURF from the white grub larvae, but you should also use imidacloprid (Merit® fertilizer granules or Dominion® 2L Termaticide/Insecticide liquid concentrate) to provide your landscape ornamentals with some protection against the ravenous Japanese beetle adults. Here’s a link to our informational page on dealing with Japanese beetles, the very worst of the adult stage plant-eating-beetles (click here to visit our ‘Japanese Beetle Control’ page).
Many questions come to us during the spring rush to plant annuals and perennials. You’re out there working the soil uncovering a fair amount of grubs. Well, the experts say it takes more than a dozen grubs per square foot to cause visible turf injury, but we’ve found that one grub on its own can cause a noticeably bad patch of turf (3 to 4” across). But, that’s for turf, not petunias and other ornamental plants. We can’t tell you if grubs injure landscape ornamentals, but we highly recommend that we treat your beds with imidacloprid because the insecticide will provide systemic protection for the plants in that bed, against the insects that feed upon the foliage. If you treat your beds, you will indeed control any white grub that munches on the roots of a plant that has been treated ((click here to visit our ‘Japanese Beetle Control’ page). Sprinkle 1 cup of the Merit® 0-0-7 per 100 sq ft of landscape bed in March, or use the Dominion™ 2L concentrate product as a foliar spray or a root drench, using 1 “heaping” tablespoon per gallon of water.
DON’T SPRAY ANY OPEN FLOWERS WITH ANY INSECTICIDE, especially Sevin, because you’ll really hurt the honeybees. Always read and follow the label directions.
Those silly Japanese beetle traps are NOT effective because they’re baited to attract both the male and the female of the species. Sure, you’ll catch the dumb ones, but the smart ones will stay outside the trap, fornicate like hillbillies and lay dozens of eggs in YOUR turf. Even worse, you’re helping the smart one survive…think about it! If you’ve got a neighbor who has set a trap near your property, talk to them, and ask it to take it down move it to the center of their property. Again, you’ve got to treat for grubs if you like a good lawn. These traps won’t prevent grubs!
Milky spore is a huge rip-off! At the field day at MU an elderly and wizened entomologist explained how today’s organic product sold as “milky spore” is NOT pathogenic to the grub worm population! There’s a problem in the manner in which this product is manufactured…so don’t fall prey to this cock-and-bull “feel good” product. Years ago, when milky spore was effective, it was fermented using dead insects (adults and grubs) as the source of the lethal bacterium that killed the beetles. No longer, though. Plus, if you opt to use milky spore, you shouldn’t use an insecticide, because a certain amount of grubs are required to maintain the bacterial population. Use of an insecticide eliminates this possibility. Safe your money and don’t get ripped off by milky spore!
(Note: This blog was originally published on Oct. 1, 2012)