Insect


From late August until November it’s time to start pulling out the carrots and parsnips. In itself the carrots are a very easy crop to grow. As long as you make the ground nice and loose they will grow. If you use crop rotation most of the plagues will stay away.

Carrots have only one major plague on them, the carrot fly (Chamaepsila rosae), which can do a lot of damage. It is not the fly itself that does the damage, but the larvae creamy white maggots that do the most damage. The fly lays their eggs next to the carrot and the maggot starts digging and eating.

The carrot fly can have up to 3 generations in 1 year after that the larvae lie dormant for the winter. While the 1st generation of larvae only eat the little hear roots of the young carrots, it is the 2nd generation that does the most damage. They eat themselves straight trough the carrot leaving brown boring holes in it. Making it inferior in taste and, well it doesn’t look very appetizing either. Also carrots that have damage cannot be stored well.

Now except for pesticides which are not an option for me, what can we do?

Positioning.

The carrot fly does not like wind, so if you can, put your carrots unsheltered from wind. I my case there is not to much wind in the garden so I need a different solution then this.

Crop rotation

The larvae lay dormant for the winter in the soil. So if you put the carrots somewhere else next year, tough luck for the flies!

Earth care.

If the soil is disturbed by for example thinning, harvesting or walking  it is easier for the fly to lay the eggs and the larvae to get to the root itself. So thin early and don’t disturb the soil.

Onions.

800px-Two_colors_of_onions

“According to Misses E. Smit from Westernieland, carrots in her garden grew undamaged and more beautiful if she planted some onions in between them. Where she got this knowledge is unkown to me. ” This is an passage in an article from the Dutch Phytopathological Society in May 1923. This article further teaches us that shallots have the same property. According to Mister Heidema, the author of the article, the repelling properties of the onions comes from the strong scent which is not appreciated by the flies.
So unions, shallots an garlic work well, I’ve tested it and until harvesting the unions and the garlic I did not see any carrot flies. Remember for onions to efficient there need to be lots of them, think 1 row carrots, 1 row onions.

Tansy (Tanacetum vulgare).

Another effective plant against wormflies is the tansy, in dutch it is called boerenwormkruid, farmers-worm-herb. Tansy has a mix of oils and one of them is called Eucalyptol, which is used as a insecticide an insect repellant (and a number of other things). The tansy also contains camphor which is also used to repel moths. If you break a leaf and rub it on your finger you smell those two clearly.

tansy_cropped

It turns out that the tansy is a very versatile plant;

-Tansy is highly toxic to internal parasites, and has been used by herbalists to expel worms for centuries.
-It can be used to keep flies, moths and even ants out of the house by hanging it in the windows.
-It keeps flies and worms away from berries.
-And, my wife is going to love this: it can be used as a natural dye in colouring wool to a golden yellow.

I can also find lots of recipes where tansy is used, like this one:

‘Beat seven eggs, yolks and whites separately; add a pint of cream, near the same of spinach-juice, and a little tansy-juice gained by pounding in a stone mortar; a quarter of a pound of Naples biscuit, sugar to taste, a glass of white wine, and some nutmeg. Set all in a sauce-pan, just to thicken, over the fire; then put it into a dish, lined with paste, to turn out, and bake it.’
Tansy is a flower that grows a lot in the area around our house, so I think I’m going to cultivate some next year among the carrots, and probably in other places in the garden. For now I picked some here and there and put in the windows and amongst the carrots. And I’m drying some seeds.

Oliva

The Absinthe Drinker by Viktor Oliva (1861–1928)

One more thing….
According to wikipedia (and others) the tansy is toxic for herbivores (some among them horses) and humans (if eaten in large quantity) mainly because it contains Thujon. One of the components in Absinthe and the component that made it prohibited in 1907, however you will probably die of alcohol poisoning before thujon poisoning. In the Netherlands Absinthe is legal again since 2004.

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Our vegetable patch is more and more looking like a marigold (Tagetes patula) plantation, although it looks very nice and colourful, some of them are getting a bit out of hand. Half a meter wide and about the same height. There won’t be any roundworm alive in the earth after this attack!

Serious, the reason for the Marigolds in the garden is roundworms. Roundworm, nematodes for scientists, are little worms that live everywhere. Soil, water, roots, animals and humans; they are all over the place. You can’t see them with your own eyes but under a microscope you will find up to 50 in a cubic centimetre of soil. In a square meter of soil there are up to 10 million of them.

According to wikipedia there are 80.000 known species of roundworms and there are and estimated 500.000 different species. One group of this half a million, targets the roots of plants, specially perennials but also potatoes, eggplants and tomatoes. Against these roundworms you can use the marigolds, it is not that the worms are scared away by them. Although everything looks peaceful there is an underground war going on.

Some science for the other geeks: the inner skin of the roots (endodermis) of the Marigolds contains chemicals called thiophenes. When a roundworm enters the cells of  this inner skin, it forms peroxidase. The combination of this peroxidase and the thiophenes create O3 (ozone), this aggressive form of oxygen burns the roundworm. So far for the peaceful vegetable patch.

The bee doesn’t care about any of this and comes for very different reasons to the Marigolds.

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This bumblebee is enjoying the nectar from a thistle in the field behind our house.

Bumblebee

Bumblebees are of the same family as normals honeybees. They pollinate plants same way a bee does. They are social insects with a queen and workers. They can sting but they don’t have a barb on their stinger so they will survive the sting – unlike a bee. Bumblebees can, because of their longer hair, survive colder temperatures than normal bees. Therefore, they can also be found in the tundra and higher altitudes such as mountains. There are 400 kinds of bumblebees, this one is a Bombus terrestris.