Tuesday, May 14, 2013

pests: problem solving in the garden

Like many other gardeners I know, I love kale. The last 2 years in a row, I've had a lot of trouble with what seemed to be root maggots, eating the roots and main stalks of my kale and broccoli to the point of their death. Kale is one of my favorite garden vegetables, so I haven't been able to give up on it, but it's been super frustrating.

Last spring, when I found maggot infestations in the roots of my first planting of cucumbers, I decided to investigate a little bit further (this would not be a typical plant for root maggots). I started to notice that where ever I found little white larvae, I would also find tiny white organisms with legs (millipede babies), and small millipedes (closer example here). Are there two problems, or are they all related? Still slightly unsure on this but I am thinking two.

Millipedes feeding on a decaying artichoke flower. If you look closely you can see babies as well.
After some research on millipedes, it seems pretty likely we have an issue with overpopulation. The garden provides nearly ideal millipede conditions, with lots of decaying matter in the form of mulch and woody compost, and steady moisture. Millipedes aren't usually problematic in a garden, but they will eat what ever is at the site of their hatching, including the roots of young seedlings. So in the event of an overpopulation, seedlings may start to become a more likely food source.

Lacinato kale, interplanted with arugula
This year I'd been holding my breath a bit. It's been drier and warmer than usual this spring, and my kale has been growing strong. We had the first rain in quite a while this week, and when the sky started to clear I went to check on the garden. Seeing the kale all flopped over from breezy rain reminded me of past issues, so I started poking around. I found that nearly every single one of them had many millipede babies in their roots, and at least one with maggots burrowing in the main stalk. I also found quite a lot of mature millipedes. I cleared out all offenders that I could, and then moped off feeling pretty grumpy and defeated. But yes I know, moping doesn't accomplish anything... 

I tried to feel out the situation to see if a solution would come to me. I thought of all the usual things I knew of... insecticidal soap, neem oil, wood ash, coffee grounds... but none of them really felt quite right, and then coffee came to mind. Brewed coffee. The feeling was to brew some coffee and pour a bit at the base of each plant - enough to saturate the immediate root supply. I haven't heard of doing this, but it just had that feeling of effectiveness, you know? Do you ever try that? To just feel for a solution? Sometimes I have come up with amazing solutions this way. I don't know if this one will work, but I'll be watching closely.

Later, I looked online to see if I could find any literature on using coffee as a pesticide, and actually found a few mentions of using brewed coffee as a spray on plants to deter slugs. Apparently the caffeine is toxic to them. I have to say, it was satisfying to find some backing to my less than scientific vision.

I used the grounds too.
If anyone has encountered issues with root maggots or millipedes and has found an organic way to deal with them, you have my full attention. This has probably been my biggest gardening frustration (lucky? maybe). It's hard to see beautiful plants you have grown up from seed just suddenly waste away.

While life will surely go on if I lose all my kale, I like to try to tackle these challenges and not give up. I've become a more patient and more enduring person in my day to day life by sticking it out with these kinds of perplexing challenges in the garden.


  1. I planted broccoli for the first time this year; they sprouted beautifully, and the leaves looked great... until holes just seemed to appear and they stopped growing. I couldn't figure out what bugs were eating my plants, until I looked even CLOSER and saw these grub-ish looking bugs that were the EXACT green color of the broccoli and I had missed them the whole time. I pulled off about 15, but alas it was too late, and nothing because of my poor plants. All that is to say, the whole brewed coffee thing sounds brilliant; I'll have to try it next time!

  2. i like your willingness to try new things abby. i have hope for you! and you can always grow kale in containers until you figure out a tried and true solution:)

  3. I'm having problems with root maggots as well. Last year they just got into my salad turnips, and I had good results with covering new plantings with floating row cover to keep the adult flies from laying eggs near the plants. This year I got lazy, and am paying the price, as my cole crops are suffering badly.

    Anyway, all the reading I've done online seems to imply that the only solution is to cover crops for the duration of their lives with row cover. It doesn't look the greatest, but it should do the trick. You also have to rotate your plantings -- in areas where you've had an infestation in the past, there will likely be maggots left in the soil, so if you cover over that area, they will come back up again inside the cover and lay eggs.

    Interestingly, this year I have also noticed millipedes with the root maggots (mainly on the roots of my bok choi). There have only been a few, but last year I hadn't noticed any. I have a feeling that they are either attracted by the rotting root matter left by the maggots, or feeding largely on that rather than the living roots themselves.

  4. It is best to use any type of spray in the early morning or the cool of evening. Do not spray when temps are above 80 degrees Fahrenheit! Your plants may "burn" or have a reaction to what you are using in excessive heat. This is known as "phytotoxicity."