Turfscape Talks

Welcome to Turf Talk! What about grubs and grub control?

Mike McDade on 02/17/13

Hello and welcome to my blog, “Turf Talk”. Let me begin with a formal introduction. I am Mike McDade and I started Turfscape in 2000 after having worked for Tru Green, Turf Guard, McFarland Tree Service, Mountain Top Tree Service, Heart of Oak Tree Service, The City of St. Clair Shores, and The Detroit Tigers. I am very happy and fortunate to have made my living working outdoors with plants and trees for the last 25 years.

Let’s get down to some nitty gritty turf talk. As I am out talking with clients and potential clients, one of the more important decisions they have to make regarding their lawn care program is whether or not to include grub control. Of course, from my point of view, as a business owner who applies such things for money, I am inclined to tell you that you should include it. But perhaps you have concerns about environmental impact or the impact to your own budget. I believe that this, like most other decisions, should only be made after knowing all of the facts. Then and only then you can make the decision that is right for you.

First let’s spend a year as a grub. As Carl Spackler said in Caddyshack, “I got to get into this dude’s pelt and crawl around for a few days.” So let’s start at the beginning. Grubs are the larvae of a variety of different beetles: Japanese Beetles, European Chafers, even the common June Bug. They hatch from eggs that are laid within the turf as a result of the mating practices of these beetles. This happens from June-September in our climate zone. While you are worrying about what these creatures are doing to your rose bushes, trees and shrubs, what you really ought to be concerned with is what their slimy little offspring are going to do to your lawn in the weeks and months to come.

As we head into mid-late summer these eggs hatch and small grubs with voracious appetites emerge. They are born into a wonderful salad of turf roots thanks to the foresight of their mother. And they eat, and they grow…quickly. As they grow they molt, shedding their skin, and gaining another body segment known as an instar. The larger the animal grows, the more insecticide is required to kill them. At least this was the case when we were limited to old fashioned organophosphates. Now that doesn’t sound like anything that anybody wants to hear, more pesticides, and it isn’t. So, the friendly chemists over at Bayer developed imidacoprid (Merit). This chemical is taken up systemically by the plant which limits its mobility in the environment. It also means that it is specifically targeted to the pests that feed on the roots of the treated plants. The grubs must eat their own body weight of the material to die. Merit takes time to be metabolized into the plant, so apply it in July and August to prepare for the grub damage that would happen in September and October.

By autumn, these voracious critters are feasting and growing at their highest rate. They effectively prune your grass off at the roots. Grub damage is easily identified by pulling up on the dead leaf tissue and finding that it is no longer anchored into the ground. Had the turf died from other factors, the dead roots would still anchor it firmly as you pulled on it. It takes 10 grubs within a square foot of turf to cause noticeable damage. Less than 10 are negligible. Remember, you seek grub control which is not necessarily grub eradication. Grub damage is often masked by drought stressed turf that turns brown in mid-late summer, so an awareness of exactly what to look for is vital to diagnosing the problem. If you have not applied Merit in the preceding months, you must now use an organophosphate, such as Dylox or Sevin. The sooner the better since it takes more to kill them as they grow larger.

As winter begins and soil temperatures fall under 40 degrees (as late as December) the fattened grubs burrow deeper into the soil to hibernate and protect themselves from the elements. They re-emerge in the spring as fat, lethargic grubs that can be as large as your thumb. It is important to know that at this time treatment is nearly useless. Not only are they not feeding significantly, but it would also take much more insecticide to kill them. Those insecticides would also have to be organophosphates because Merit would be useless in the spring. So you can see that knowledge of the grubs’ life cycle and the products used to control them is critical to ultimate success, the protection of your turf.

As a turf professional I would recommend including grub control in your annual program. However you are the owner of the site, and it is you who must control the budget. There will often be years that grub infestation just does not happen. It is impossible to predict when infestation will occur, so consider the costs of turf renovation if grubs do cause damage. The choice of whether or not to include treatment for grubs is yours, and now hopefully you can make an informed decision.