Grubs in my compost bin

Asked October 5, 2015, 2:15 PM EDT

We have a compost bin that we got from Metro. I think it is the Free Garden bin. Yesterday, I was using the aerator to mix the compost and I found A LOT of grubs in the compost. I'm not sure what type of grubs they are or if they are something that I need to worry about. I took a photo of them (there isn't anything in the bin to provide scale, but they are about an inch long). I also have a video but I don't think I can upload it to this site. The things we primarily add to our compost are: old veggies/fruits, coffee grinds, egg shells, grass clippings and fall leaves. I would appreciate any information that you can give me such as: 1. what they are / what they will turn into 2. if they are anything that I should worry about and if so, how do I get rid of them without compromising the compost 3. if it is ok to put the compost in my vegetable garden with them in it We live in Beaverton. Thank you so much for your help with this. Terry

Washington County Oregon compost grubs

1 Response

Terry - responding to your email by the numbers (and thanks for the photo):

  1. These are the larvae and pupae of some flying insect. When they mature they will fly away.
  2. I personally don't worry about them when I find them - even in great numbers. The only thing you could do to get rid of them is to turn the compost, adding some nitrogen source. Personally, I like fresh juicy grass clippings, or alfalfa pellets (buy at the feed store 40# bag), and 25-0-0 will do as well if you dissolve in water first. Turning and adding additional nitrogen will cause the compost to heat up, and the larvae will die and decay, contributing their own nitrogen (proteins) to the compost. I suspect, based on what you are composting, that the pile is too wet. If so, add any kind of dry thing - autumn leaves are great, but really, have you had so many in the last months? Also really good is paper of all sorts - paper towels, napkins (nothing from the bathroom, please!), shredded office paper, junk mail, newspaper. Go easy on shiny colored ads - they add clay and heavy metals to the mix. Hand torn will do, but there's nothing like machine shredding to make the paper break down in a jiffy. Never have food waste as the bottom layer of a compost pile (in contact with the soil) nor as the top layer. ALWAYS cover food scraps with something - leaves, weeds, any kind of plant material. Exposed food is an invitation for flies to come and lay eggs.
  3. Yes, it is OK to spread this compost with the larvae and pupae living or dead, since they will just mature and fly away unless the cold gets them first.
Having said all that, I don't much recommend working soil amendments into the garden at this time of year. Two exceptions would be lime and sulfur, which require a long time to change into forms that plant roots can recognize. Definitely not manure unless it is already well rotted. No point in applying nitrogen now, and letting the rains move it beneath the reach of plant roots next spring and summer.

On the bright side, the presence of these insects indicate that the fly who laid her eggs in your compost found just what she needed, and that indicates that you are on the right track for successful composting: a food source, moisture, warmth, and shelter.