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They are the same colour and shape as caterpillars... Yet, they are not caterpillars; they are a distant relative of the wasp! They also do not behave in the same way as caterpillars in the garden. Their real name is the "sawfly".
The symptoms
The damage caused by sawflies is the same as that caused by real caterpillars. However, the behaviour of the beast is very different, which means you should not get them confused: the sawfly forms itself in to an "S" shape and adopts a defensive poise. These beasts always feed in tight groups on a plant. A single leaf can harbour a dozen of them.
Lifecycle
The larvae appear at the end of spring and through the summer on plants that are peculiar to the sawfly. In the garden, you will find them on roses, alder and gooseberries. The development of the sawfly is very rapid. Often you will only notice the damage once the insect has already left. In this case, any intervention is futile. A plant attacked one year will not necessarily be attacked the following year.
How to fight them
The only way of fighting the sawfly is by using an insecticide, such as spraying with a solution containing pyrethrum extract (insecticide from plant origin). You can also remove the beasts by hand, as a plant rarely has lots of them at any time. The use of Bacillus thuringiensis that we use against real caterpillars has no effect on these insects.
How to avoid them
You cannot predict when the sawfly will attack. It is therefore impossible to avoid them arriving in the garden. In any case, the damage they cause is very punctilious and does not justify any particular means of prevention.
Good to know
The larvae of the sawfly, known as the false caterpillar can be annoying for roses in the spring. However, the adult insect, which does not resemble a butterfly in the least, is in reality one of the allies of the gardener. It is actually one of the predator insects that feed on other insects that it hunts. As many things in the garden nothing is black and white! - Photos (1)
False caterpillars
False caterpillars (Sawfly)
Author: Jean-Michel Groult
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