What Insect is Feeding on my Vegetables?

Q.This year many of my vegetables have been affected with a tiny white insect feeding on the roots. The onions, beetroot, carrots all seem to have it. It moves quickly and looks like a tiny white centipede. I cannot identify it from any books. Do you know what it is and how to deal with it?

(Mr Nicholas Whieldon, 2 October 2008)


A.It’s very hard to give a specific answer without seeing the insect in question. The best we can do is offer some general suggestions for preventing and getting rid of vegetable pests.

As you’ll probably already know, as you’ve done your research, beetroot, in particular, is usually relatively pest‐free, and while carrots and onions each have their own fly pest, neither exactly fits your description. So we’re unable to identify your particular insect but we’ll try and advise you on how to prevent insects eating your root vegetables in future.

Preventing Pests

Both carrot and onion flies are airborne pests. The adult lays its eggs on the plant and the pupae bury down and eat the roots. The adult flies are attracted by the smell of the plant especially when it’s being disturbed by thinning or moving. In the past gardeners have used paraffin‐soaked sacking laid between the rows to disguise the smell. A more palatable alternative is to grow strongly scented herbs such as basil, rosemary or sage in between the rows.

Alternatively, to prevent airborne pests landing on your plants, use a polyester row cover or horticultural fleece (available from garden centres). These lie gently over your plants, allowing water and air through but keeping out the pests.

Millipedes will sometimes feed on roots. Don’t make it easy for them by leaving garden rubbish around in which they can hide. Clear the space around your vegetable plot so millipedes will have to be quick to cross the gap without being eaten by a bird!

Getting Rid of Pests

Of course, if you’ve already got insect pests, you won’t care if they’re airborne or earthbound: you’ll just want to get rid of them! So once you’ve discovered that your plants are infected, treat them with a pesticide. If you prefer to keep your food organic and chemical‐free, you’ll find a wide variety of excellent natural pesticides available at your local garden centre. Just follow the instructions given.

Harvesting your affected crops early may help to stop the bug spreading and surviving. After harvesting give the soil a good deep tilling to further destroy any remaining insects. And, the following year, plant something completely different in the areas affected.

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