Reader Questions – 08-27-08

Heather has some questions about fruit flies, mites and small worm bins

I recently “adopted” two bins of red wigglers from a friend who
didn’t want the worms anymore and both bins seem to have a fruit fly
infestation. I have tried to remove some of the bedding as well as try
to squish the fruit flies . My own bin doesn’t seem to have any fruit
flies but does have the mites. I thought those white mites broke down
the food for the worms or that the worms ate the mites.
What can i do to get rid of the fruit flies (i’d rather not touch the
worms if possible) and should i be concerned about the mites in my own
Also, the bins that i have are mini starter kits (ice cream
containers) that my children received from school. Should i be
combining all three little bins into one big bin/worm chalet? I’m
just afraid i may harm them in the process.
Thanks for your help! Your site is THE BEST one that i’ve been to
for information on vermicomposting.
cheers, heather

Hi Heather – thanks for the kind words.
Fruit flies are the most annoying worm bin pest for sure. I still get bad infestations from time to time myself (actually just coming to the end of a bad invasion in my basement). Your best bet is to 1) Eliminate the food source – remove all decaying fruit/vegetables etc from the tubs; 2) Make some traps using apple cider vinegar. Simply pour the vinegar in a glass, add a drop of dish detergent (decreases surface tension causing the flies to sink), put Saran wrap over top, then puncture with a fork.
3) Vacuum up as many adults as you can. This really helps to reduce the number of ‘breeders’, thus leading to a population crash more quickly.

To be totally honest, it often takes some time to get rid of a bad infestation, but these steps should definitely get you on the right track.

White mites are very common in worm bins – especially plastic bins with very high moisture. I have quite a few open systems that get lots of air flow and I don’t see them at all. Any Rubbermaid bins I set up and add food waste to invariably seem to end up with mites at some time or another. Bottom-line, you don’t really need to worry about them. They may be an indication of too much food building up in the bin, but all in all they are pretty harmless.

As for combining the little bins into a bigger one – that’s probably not a bad idea if you want to boost your population and compost more material. On the other hand if the small tubs are working really well, there is no reason not to continue with them. Once they get pretty full and have lots of castings (dark soil-like material) you should harvest the compost and start them again – or simply start up a new bin. Check out my ‘Getting Started‘ page for more info about that.

Hope this helps!

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  1. I have to chime in on the vacuuming part – I had an infestation issue in the last couple months and I was so surprised how quickly this helped. Everytime I saw the fruit flies whooping it up I took the vacuum out and within a few days there were very few left. I also did not feed the system for 2-3 weeks. These 2 tactics seemed to take care of the problem.

    • Jodi
    • July 26, 2009

    A spider built a web over our worm bin. Every time we open our bin to add food…. the spider gets himself a scrumptious meal and we have less fruit flies….it’s a beautiful thing!

    • charu
    • October 8, 2010

    I started a worm bin 2 weeks ago – it is simple plastic bin, I have lots of bedding and red worms and food.
    This week I am having lots of fruit flies!!!
    What can I do?
    thank you,

    • Norma
    • June 11, 2011

    Once you get rid of the fruit flies the trick to keeping them away is to freeze the scraps before putting them into the bin. I was told this a couple of years ago and it works.

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