Japanese beetle grubs?

Question: This spring i built a 5' x 11' raised garden which I filled with bagged soil (garden and potted) from COSTCO.  I am now finding this huge numbers of grubs.  Ace said to use Traizicide but that is a neurotoxin (safe of course????).  Decided to pull out carrots and try with remaining tomatoes, peppers, and cucumbers.  Other half of same garden is strawberries which I do not know if it is ok to use on.  Will try and attach photos.  Any assistance would be greatly appreciated.  If I kill grubs will they be gone or return? Thank you Ken Noreyko

responder: Hania Oleszak  Replied July 18, 2023, 5:45 PM EDT
response: Hi Ken, There are several different grubs that can be found in a raised garden, many of which won't affect your vegetables. Before treating for them, it would be best to identify exactly what kind of grub you have in your garden. To do that, we would need a physical sample of the grubs, which you can bring over to CSU's State Plant Clinic (more information here: https://agsci.colostate.edu/agbio/plantclinic/). Thank you! Hania

responder: The Question Asker Replied July 29, 2023, 4:09 PM EDT
response: I dropped off a bunch of live grubs on Thursday July 20th and have heard nothing back.  I assume this is standard time to process?  Just don't wish to get lost.Thanks,Ken Noreyko  On Tuesday, July 18, 2023 at 03:45:08 PM MDT, Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied August 04, 2023, 6:04 PM EDT
response: Hi Ken,  The Jeffco Extension office is short staffed right now, so it may take longer to get your sample. In the meantime, I wanted to share more information with you.   The grubs in the soil are definitely NOT Japanese beetles grubs because they can only survive by feeding on turf grass. Many other species of grubs exclusively on turf grass, narrowing down the list of possibilities.  In my experience, the vast majority of grubs found in soil are usually the Bumble Flower Beetle grubs. They feed and thrive on soil with high organic matter. They are also often found in compost piles, container gardens, etc. These grubs feed on decaying matter and don't harm the plant. They are actually beneficial because they break down decaying matter. Here is more information: https://webdoc.agsci.colostate.edu/bspm/arthropodsofcolorado/Bumble-Flower-Beetle1.pdf  And here: https://extension.usu.edu/pests/ipm/notes_ag/veg-bumble-flower-beetle  You can leave them in the garden, or since they are in high numbers, you could spread them out to other places in your landscape. Typically pesticides are not needed to control the grubs. If you choose to use the Traizicide, note that it is a broad spectrum insecticide so it will impact other beneficial insects/arthropods in the garden. Be sure to read the label and follow directions explicitly especially since you are growing vegetables/food for human consumption. The label should indicate if it is safe on strawberries.   Hope they can get you a confirmation on the identification soon. Happy to answer any more questions.   Thanks,  Lisa  Lisa Mason Horticulture Specialist & Entomologist Colorado State University Extension, Arapahoe County

responder: The Question Asker Replied August 04, 2023, 7:00 PM EDT
response: Thank you so very much for the information!  It is truly appreciated.  I still believe they were in bags of garden soil I purchased at COSTCO so am surprised by how many there were.  Since they are beneficial I will make peace with them.  (they were so plentiful I was putting them in lids and I believe the birds were enjoying them).  Best,Ken  On Friday, August 4, 2023 at 04:04:19 PM MDT, Ask Extension <<personal data hidden>> wrote: