Tuesday, September 3, 2019

Yikes--Bugs in Compost!!!

By Yvette Henson, CSU Extension Agent, San Miguel Basin

Last year, my compost pile became infested with pill bugs—what most of us call ‘roly poly’s’.  In the early spring, I like to add an inch or two of compost to my raised beds in preparation for planting, I noticed a solid layer of all sizes of pill bugs covering the top of my compost pile!  I wish I had taken a photo but I wasn’t thinking of documenting it at the time.  I did my best to remove that layer with my shovel and tossed them into the woods.  I went ahead and applied the compost to my garden beds.  Most references tell us that these little arthropods don’t do much damage to our plants—they simply munch on organic matter.  So, it makes sense they would be in a compost pile.   There are other positive attributes to these little buggers too.  However, they ended up thriving and multiplying in my beds, eating almost ALL of my carrots as soon as they germinated and so I had to replant!  In my short mountain growing season, replanting was a real bummer (not to mention the loss of the seeds)!  I spent quite a bit of time picking them out as I found them, luring and ‘trapping’ them under cardboard so I could toss them or squish them.

  While this was somewhat satisfying as ‘revenge’ it didn’t amount to much reduction in population. They kept hidden and multiplied in the crack between my soil line and the raised bed walls.  Finally, I got and applied an organic granular product containing spinosad that was somewhat effective.  It was labeled for pill bug control.

Pill bugs or’ roly polys’

Another insect I have seen in my compost pile are grubs! I saw these this year when I was adding partial compost to cover newly added food scraps. Beetle larvae are appropriately called ‘grubs’ and have a dark head, 6 legs near the head and they curl into C shape.  Some grubs feed on plant roots so you don’t want to add them with your compost to your garden.  Instead, screen them out of your compost pile when you find them.  You can feed them to your chickens, if you have any, or leave them for wild birds.  By the way, chickens don’t favor pill bugs for snacks. 

A ‘Grub’ ie beetle larvae

You might see maggots, fly larvae, in your compost pile if you add cooked or oily food or meat or some manures to your compost pile.  Too much nitrogen and water is a good breeding ground for them too.  Maggots have a pointed head and no legs (see the photo below).  Maggots are a good protein source for chickens and birds.  When they mature, they will fly away.   Besides not adding the above to your compost, keeping it just damp enough, like a wrung out sponge, and burying kitchen waste as you add it, will help prevent maggots from developing in your compost. 

The best way to prevent or rid arthropod invaders from your compost is to add a nitrogen source by layers to the compost as you turn it.  Keep the nitrogen in balance with the dry brown carbon in your compost. Some nitrogen sources are fresh grass clippings, alfalfa pellets, blood meal or some other fertilizer high in Nitrogen.  The way I ‘turn’ my pile is by moving my compost from one bin or ‘pile’ to another.  This puts what was on top on the bottom and what was on bottom on top.  The reason we do this is to add oxygen and a food source (the nitrogen) for the microorganisms that do the work of turning the waste into a great soil amendment.  These microorganisms will heat the pile as they feed and multiply.  A temperature of around 145 degrees F should kill most of the ‘critters’ and their eggs, plus it will help your compost break down and ‘finish’ more quickly.   Ideally you should turn your compost whenever the temperature in the center of the pile gets below 70 degrees F,  unless it is finished.  Turning it once in the spring and once in the fall is usually sufficient.  Using a compost thermometer to monitor temperature is a good idea and they are relatively inexpensive.

For more information on composting in general see,

Sometimes we get other pests in our outdoor compost piles and our indoor worm bins but I will save those for another blog, if there is interest.

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