Gardening > Garden Pests

A q&a article on garden pests:

Question

How can I organically prevent caterpillars from eating cabbages?


The Green Chronicle replies...

The most straightforward traditional method is just to keep a close eye on your cabbages and to hand-pick the caterpillars off. Chickens like them. There are predators of cabbage white caterpillars so if your garden has good biodiversity there are several types of parasitic wasps, as well as birds, ground beetles and hoverfly larvae that will help you out.
You might try a wider spacing for your Brassicas as this should slow the spread of the caterpillars, and inter-planting with different crop plants, and or flowers, should make it more difficult for the female butterflies to find your cabbages. If you are really stuck then organic growers can use a microbial spray called Bacillus Thuringiensis (BT) which is totally specific to caterpillars. In essence BT is just a kind of biological control, and should be available in most good garden centres. I would recommend above all else vigilance - if you see them pick them off and put them in a bucket. My problem this year is pigeons, but caterpillars have kept me busy in the past.


Question

I just planted my first herbs. A very small garden consisting of basil, rosemary, cilantro, and thyme. These are planted in a window box. I've been noticing holes dug in the soil near the plants, about the diameter of a golf ball. I am wondering what might be doing that, and how to stop it. So far it does not seem to harm the plants, but I want to prevent this mystery critter from doing any more damage. I live in Wisconsin and the animals that are typically around are chipmunks, squirrels, rabbits, bats, and birds. Any thoughts?


The Green Chronicle replies...

It sounds most likely to be a bird after something other than your plants. If it is it may actually be that the bird could be an ally, it might after all be an eater of pests. If you really want to stop the bird or whatever it is digging these holes then I would recommend a light net, or a small piece of gardeners' fleece over the window box at times when you think the damage occurs.
Enjoy your herbs!


Question

I have heard about protecting young plants from slug attack using copper wire and a potato - do you have any details re. this or any other anti-slug options?


The Green Chronicle replies...

Whilst harnessing the electrical charge which can be generated from a potato (I would guess a lemon has a greater potential) seems an attractive option I have to say that trying to keep slugs off with an "electric fence" might be described as going about the problem the hard way. Whilst I have experience of electric fences to control large stock, I have none of trying to ward off invertebrates, but it seems likely to me that you would have to prevent your wire earthing out. Now I know a digital clock can be powered with a piece of fruit, but just how much veg. might be protected with a potato-powered wire I don't know. Honestly, why don't you try biological control instead. Put a pond into your garden and get some frog spawn in it, the frogs will eat your slugs for you. Encourage hedgehogs and other slug-eating wildlife, a balanced eco-system is the best strategy for any organic gardener. You could also try buying slug-eating nematodes to inoculate your soil; they do require a nice warm soil, but would certainly knock back your slug population once established. There are many many anti-slug measures that I would try before experimenting with plant-powered electrics. Here are a few more to put alongside biological control: egg shells; bran; sand; saw dust; ash; beer traps.

I know that slugs can be annoying, but don't despair, even if you have to go out with a torch a pick them off the plants by hand, they can be defeated.


Question

I can't for the life of me identify the pest that is eating my Asiatic lilies. They look like tiny orange slugs, maybe 1/8" long but with a black head (so obviously not a slug). They crawl up the lily stems and systematically chew up the leaves until they are completely gone. There will be a dozen or more on each plant, and they cover themselves in what I assume is excrement (looks like soil). I only have about ten lilies spread out in a thirty foot bed, and these pests are eating all of then and not touching anything else. Can you identify them for me?


The Green Chronicle replies...

Hi,
as soon as I read your story I knew what we are dealing with, a friend of mine had it in his back garden last summer. The prognosis isn't good I am afraid. It is a truly disgusting looking pest isn't it? The excrement covered bugs are the grubs of the lily beetle, and I wonder whether you saw the bright red adult stage at all. I am afraid that from an organic point of view only picking the grubs off is a reliable treatment. Because of this it is normally only possible to protect a very limited number of lilies. The ones you can't defend in this way will be reduced to bare stems in short order.
Sorry not to bring better news, but the lily beetle is a devastating pest of lilies.

If you have any questions about garden pests, e-mail us and we may be able to help!


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