In the past I’ve always sprayed my lawn with soapy water using a hose-end sprayer. Since grubs don’t like the soap, they come to the surface where the birds can eat them.
Would this method work with Japanese Beetle larvae too?
And, when do Japanese Beetle larvae hatch?
Thank you for contacting the Toronto Master Gardeners. Toronto Master Gardeners do not recommend the use of any homemade remedies. We do have numerous postings on how to treat Japanese beetles and grubs in your lawn
Simply type Japanese Beetle and Grubs in Lawn into the Find it Here Search Box located to the right of the page
The following information is from a two of our archived posts:
“There are two periods when grubs can be targeted by nematodes, in the spring when soil temperatures are above 10°C (often early May to early June) and again in the fall before soil gets too cold (mid-late September to mid October). Your best option is applying during both the spring and the fall to get maximum coverage and protection!
Nematodes search through the soil, locating a host and then enter through natural body openings. A natural bacterium is released that is fatal only to the insect, which dies within 24 to 48 hours. The nematodes reproduce and continue to eliminate grubs as long as soil moisture conditions allow (6 to 8 weeks).
Application should be done when soil temperatures are above 10°C, preferably above 15°C. The lawn must be kept moist for two weeks after application. The solution must be able to penetrate to the root zone area, thus a properly dethatched lawn is advisable. Nematodes will infect grubs within 2 days of application and kill them within 14 days. They will not kill the entire grub population in your lawn, but will reduce it drastically.
Since the grubs are at a stage when the use of beneficial nematodes is effective (early May ), you could overseed at the same time. Both the treatment and grass seed require watering. If the nematodes are effective, the grubs should be dead before the new grass roots form.”
“Generally, to control Japanese beetles you can either control the adult or the larvae. The best method (although still time consuming but strangely satisfying) is to go out in the early morning or in the late evening when they are not as likely to fly around and simply knock them into a small bucket/jar of water (add a few drops of soap) where they drown. You will need to begin this process at the end of June or the beginning of July and continue until sometime in early August.”