Ohhhhhhh....Grubs in the Garden Soil - Ask Extension
I use raised beds to garden in. We built two new beds last year and filled them with topsoil from a construction site....purchased from a local garden...
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Ohhhhhhh....Grubs in the Garden Soil #310192
Asked March 30, 2016, 10:03 PM EDT
I use raised beds to garden in. We built two new beds last year and filled them with topsoil from a construction site....purchased from a local garden center. I hoed up all the soil in all the beds in the last couple of weeks, to get them ready to plant...both seeds and plants and noticed that there were grubs in the soil in the 'new' beds. .....and one of the beds has an extraordinary quantity of said grubs. I mean, ALOT!!!! Every scoop of dirt has at least 5-6 grubs in it...the dirt is riddled with holes and I planned on planting green beans in this particular bed....I had potatoes in it last year. My question is this....do we treat before I plant bean seeds or wait.......(we also had grubs kill a patch of grass in the back yard while we were on vacation last year......in the same place we had scattered some of this dirt. Am sending pictures of said grubs to see if you can identify them. We haven't had much of a problem with Japanese Beetles.......only a few and I just pinch them off the plants. We do, however, have some of those big beetles....Iridescent Green & bronze "June" beetles..... Would appreciate any suggestions. Oh, and I am an Organic Gardener for the most part.
Pickaway CountyOhio
Expert Response
I am not able to identify the species of grub in the pictures. If I knew how large they were (maybe if there was a ruler next to the grub?), and if I could see the pattern of hairs (rasters) on the underside of their rear ends, I could ID them. If these are extremely large, and appear to move by crawling on their backs, they would be the larvae of the Green June Beetle, which does very little damage to living plants, preferring to feed on organic matter.
Generally, I never recommend using garden soil or excavated subsoil for a raised bed. As you've seen, you can often bring in unwanted pests. Also, in most locations this "soil" is actually subsoil, and high in clay, making your raised bed poorly drained. Raised beds work best with soilless potting mixes, or at least with a compost-topsoil mixture.
Regarding the grubs: there are no control options that I could recommend for grubs or other soil-borne insect pests in a vegetable garden...organic or otherwise. I would suggest that if these insects feed on the roots of your vegetables, that you may need to either replace the soil in the raised beds, or let the garden remain fallow for the spring, and try for a fall garden.
Thank you, Larry, for your assistance. The grubs in question are actually about an inch long......not large like a Cicada or Green June Beetle. I know exactly what you are talking about regarding the clay in garden soil.....I mix plenty of compost and chopped leaves with the soil to make sure it drains well. And continually 'feed' it with leaves at the end of every season.......and use compost throughout the gardening season to mulch everything with it. If I get a chance to take a picture of the grubs (raining now), I will send it along....of the underside of it.
