Japanese grubs

Asked July 24, 2018, 12:27 PM EDT

I have large patches of lawn with no grass and a huge Japanese beetle problem on my roses. Do you have any information about using beneficial nematodes to eliminate grubs vs Bayer Grub control? My neighbor has honey bees and there are tons of bumble bees on my pollinator friendly plants nearby. The grubs were found in my dirt near the dead grass but the photo was taken after I "moved" them onto the street Thank You, Connie Rutledge Minneapolis

Hennepin County Minnesota

3 Responses

Controlling Japanese Beetles can be a prolonged challenge. However between now and late August is the time to deal with grubs in the yard. The species of nematodes used against Japanese Beetle grubs is Heterorhabditis bacteriophora. It is commercially available. However, note that these nematodes are relatively expensive and must be applied several times as they do not live long in the environment.

These nematodes are microscopic parasitic roundworms that transport and feed on bacteria. When they find a grub, the nematodes penetrate the larva and inoculate it with bacteria, which quickly multiply within the grub's body. The nematode then feeds on the bacteria. Nematodes need to be applied to soil at night and the soil must be irrigated daily to keep it moist so the nematodes stay alive."

Here is a site where you can find further information regarding the use of nematodes;

https://www.arbico-organics.com/category/beneficial-nematodes-faqs

Bayer Grub Control is a chemical product used to kill the larval stage of Japanese Beetles. It, too, should be applied during the latter part of the summer. Here is some information about chemical control of grubs:

https://homeguides.sfgate.com/bayer-grub-control-vs-grub-killer-plus-75434.html

As a volunteer for the Master Gardener program of the University of Minnesota it would not be appropriate for us to advocate one product over another.

One more site for you to look at with regards to the application of grub control measures:

http://msue.anr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

Good Luck

One other thought. It is important to know that in fact you are really dealing with Japanese Beetle grubs. It is rather easy to determine this. Go to one of the affected areas in your yard. If grubs are present, you should be able to lift up portions of the turf. Look under the turf and see if there are grubs present similar to the attached picture.

Please let me know if any additional issues arise.