An often overlooked resource
These arthropods exist in sufficient numbers and diversity in our regions to help us fight all the native animal parasites but, for the parasites more recently arrived on our premises like the pine processionary caterpillar or the suzuki drosophila which ravages many of our red fruits, auxiliaries are sometimes absent or too few. Sometimes pest control professionals have to go halfway around the world to find insects.
It takes time and lots of experimentation before we can release them into our crops. Indeed, we must ensure that each small organism is efficient and able to adapt to our climates, but also that it does not risk becoming invasive or harmful to our environment.
New breeding insects already on the market, but also others being evaluated
Against Drosophila suzuki,
It is a micro-wasp naturally widespread in a large part of Europe which has been on the market for a short time: Trichopria drosophilae.
This tiny insect lays eggs in Drosophila pupae, so it is a parasitoid that will greatly reduce the number of eggs laid in fruit.
The females begin to lay eggs around 15°C but the releases are in the form of pupae, so they must be placed at the end of March.
I would recommend a first release immediately after the flowering of the first fruit trees, that is to say between mid-March and early April in the plain.
The pupae will be scattered, preferably in a semi-natural environment, under a hedge or under fairly dense clumps of shrubs.
The first year, the results may not be very convincing due to the vagaries of the weather, but this type of control is more of a mass control, that is to say that it is necessary to “sow” a fairly large area to have good results.
It is advisable to repeat the release operation about 3 weeks after the first and once at the end of summer.
– Paul Vignac
Against the green bug Nezara viridula,
This spotted green bug that we find more and more in our gardens and which is starting to do a lot of damage to some of our crops such as tomatoes for example, another micro hymenoptera is coming to the market: Trissolcus basalis
It is a novelty, commercially speaking, because it is a reputedly cosmopolitan parasitoid, of African origin but very widespread in the world.
The female seeks adult bed bugs to lay eggs in the egg groups as soon as they are laid. It is not uncommon for the whole of an ooplaque to be parasitized, which makes it a very effective helper. The first releases take place in June when the temperature reaches 25°C.
Currently these insects are still expensive to buy because packaged for professionals (about 90 € for 500 imagos + 30 € shipping costs). Amateur gardeners should group together in a sector to pool purchases.
It is necessary to release approximately one micro-wasp per m².
– Paul Bis
And finally a third insect: Mastrus ridens,
Hymenoptera Ichneumonidaea parasitoid of the codling moth of apples, pears and walnuts, Cydia pomonella is under study because it is not indigenous: this type of wasp, which has a filiform waist, is native to Central Asia. It is already widely used in South America, Australia and New Zealand.
It is currently being tested all over France while waiting to be authorized for sale.
It is very interesting on the third generation of codling moth, when phytosanitary treatments are no longer feasible due to the proximity of harvests.
In the coming weeks we will visit several groups of beneficial insects of our crops.
Ask all your questions during the gardening program on Sunday morning on France bleu Isère from 9 a.m. to 10 a.m. by calling 04 76 46 45 45.