A word of caution here: this post is not about organic grub control for the most part. It’s not that I don’t believe in organic grub control; it’s that I think that most folks don’t have the patience it takes for organics to work, especially once they see their lawn being decimated by grubs. And sadly, when I worked in a big box store, I was once given an award for my “knowledge of chemical pesticides.”
How can that be? I made it my point to educate myself about responsible chemical use so that I could make sure the customers were educated as well. What they did when they left the store was beyond my control. But when I had them in my area, I could at least instruct them about proper dosages, and that “more is not better,” etc.
So then, let’s discuss the two main means of chemical grub control that can be applied in the spring, the way that they work, and how and when they should be applied (because the timing is different–a few are “fast kill” with almost no residual capacity and some seep into the soil more slowly and kill more grubs over a longer period of time).
By the way, my information is based on a fact sheet from the University of Connecticut–so this is for roughly Zone 6 type gardens. Those of you in warmer climates will need to adjust your dates accordingly. You know when your beetles fly and when they are mating.
Because homeowners see damage in the spring, and because they also see grub control products in the spring, this is when most grub control is attempted. According to the experts, however, this is not necessarily when it will be the most effective. The most damage is done by the last phase (instar) of the grubs they burrow down for the winter (October is roughly the target time for us here in Connecticut, although it could be slightly later) .
Don’t believe me? Here is an excellent discussion from the folks at UMass. They talk about the benefits of using Dylox, the fast-acting grub killer mentioned below, versus the newer neonicotinoids found in brands like Grub-Ex™. To read the discussion, scroll down to the FAQs under grubs. It’s almost to the bottom of the page under “Pests.”
The summary is that the longer acting systemics are still the best bet–and in our region they should not be applied early because of the unusual weather. They should still be applied somewhere between the mid-April to mid-May timeframe because they take 60-90 days to become active in the soil. Folks, prepare your spreaders!
Because of this tricky timing, it is definitely risky to apply the fast acting controls like Sevin and Dylox. The chances of actually killing the grubs is hit or miss.
It is much better to use a chemical formulated with residual effect to remain in the soil over a long period of time. One brand is Bayer’s imadacloprid which should be applied before the beetles lay their eggs.
Another is halofenozide, found in my area in Spectracide, and commonly know as Mach-2. It has a life in the soil of 129 days. It needs to be applied while the beetles are flying–and remember, in Connecticut the Asiatic beetle, sometimes known as the “June Bug” can have a larva every bit as destructive as the Japanese beetle. I’ve seen those unassuming little brown beetles as early as late May.
(As an aside, if you don’t think it’s killing me to suggest the use of chemicals that remain the soil for 4 months, or ones that have been known to be implicated in colony collapse disorder, think again. I’m just trying to helpfully educate. In our yard, the birds are the grub control!)
Which ever grub control you choose, you must water it in with .25-.50″ of water. Do not rely on nature for this because you will be disappointed and your control will not work. Worse yet, those granules that you have spread around with your spreader will look like bird food and you will be poisoning more than the grubs. Please be responsible about this! Get a sprinkler, get a small tuna fish or cat food type can, mark the 1/2″ mark on the inside and water until that can fills to the 1/2″ mark. It’s just that simple and I don’t want to hear any excuses. If you’re not going to do it, don’t use the product.
Finally, do consider letting the birds do your grub control for you. You’ll be rewarded with lovely bird song, lots to look at, and no chemicals on the lawn, meaning that you, your children and pets can all run barefoot in the grass.