Grub control on lawn

Asked July 24, 2017, 3:25 PM EDT

We have a big outbreak of grubs and they are killing our lawn. We used an insecticide with trichforlon in it and are wondering if you would have any other suggestions as it did not kill the insects. Thank you, Betsy Lippert

Kandiyohi County Minnesota lawns and turf grub control horticulture

3 Responses

Grub control is complicated by the fact that there are several insect species which feed on lawn roots:
https://www.extension.umn.edu/garden/insects/find/lawn-and-turf-insects/root-feeding/

How serious the problem is depends on the insect. Two common problem grubs are May-June beetles and Japanese beetles. May-June beetles have a three-year life cycle. They are small and insignificant the first year and large and voracious the third year. They are best treated for in their second year. Read here:
http://hort.uwex.edu/articles/mayjune-beetles/

Japanese beetles grubs live at a depth at which they are treatable for only a short time in the spring and late summer. Read here:
https://www.extension.umn.edu/garden/insects/find/japanese-beetles/

Both of these grubs can be treated with the pesticide you've listed. But if you did not time the use of the product correctly, you will not have good success. For instance, if your problem is Japanese beetles and you applied the product in early July, you'd have little impact on the grubs, which are only now burrowing into the soil. And if this is the third year of a June beetle population, you'd do better to wait for two years (although you can knock the population down with a grubicide).

We are sure they are the white grubs, or larvae of the Japanese beetle. We applied the insecticide on July 21st - does this seem to be an appropriate time to do that?

The literature says mid-July through early September, but the JB's don't read the literature.

If the label on the insecticide allows you to make a second application, you could do that, but always follow the label instructions about timing, frequency, application rates and so on.