I have two problems. First, I built three box gardens, each 4 by 8 feet and 18 inches deep. For the past two years, I've been digging grub worms by the hundreds out of my boxes. I don't know how to get rid of them. I don't want to use any of the poison chemicals because I raise garden vegetables for my salads. I do not want my soil contaminated. Is there any other way to get rid of grub worms? People tell me that the worms came from contaminated soil; should I replace my soil?
Secondly, I use Miracle-Gro garden soil. In these bags, I've found hundreds of little yellow round egg-like things. I thought they were plant food or some sort of fertilizer, but I was told by a clerk at a big-box store nursery that they were grub worm eggs. I've enclosed a sample. What are they?
Yoshi Mizuiri, Lincoln
Thanks for sending a sample of the "grub eggs." These are slow-release fertilizer capsules that dissolve at varying rates. The capsules change color as they age and are commonly confused with snail and grub eggs.
According to UC master gardeners Martha Moon and June Bliele, the white grubs found in your raised garden beds are the larval stage of insects commonly known as scarab beetles. This group includes the June beetle, which can be damaging if found in a large infestation in a lawn.
However, not all white grubs are "bad." Some aid in breaking down the cellulose found in soils amended with horse manure or compost, converting it into nutrients needed by the plants.
You are correct in not trying to control them with chemical insecticides since this is a vegetable garden. If you want to rid your beds of the grubs, "good" or "bad," hand picking is the safest method.
More information on grubs and other lawn insects including drench tests used to determine if treatment is warranted can be found in Pest Note 7476. It is available online at www.imp.ucdavis.edu.
Or get a copy by mail. Send a self-addressed, stamped, business-size envelope to: PN 7476, UC Cooperative Extension, 4145 Branch Center Road, Sacramento, CA 95827.
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