Gardening

Trichogramma: Avispas beneficiosas para el control biológico de plagas

Hello to all gardeners! In today’s article we are going to introduce you to a type of beneficial wasps of the genus Trichogramma as one of the most widely used biological control methods . It is used against more than 28 species! How can these wasps help control our garden pests?

Biological control of pests with natural enemies: beneficial wasps

The biological control , as you know, involves using living organisms to control pests and diseases in the garden . It is one of the alternatives used to reduce the use of products that are harmful to the environment  in agriculture. These beneficial organisms  can be micro-organisms or macro-organisms (also called natural enemies ). Among them, there is a group of wasps known as Trichogramma that will be of great help in the garden to control some pests that we will see below.

Difference between parasitoid insects and predatory insects

Before I start talking to you about these beneficial wasps for our garden, I would like to remind you of the difference between parasitic insects and predators since sometimes we get into trouble. Also, it can be summarized in that if the insects had to make a horror movie they would use them as main actors …

A predatory insect is one that normally has a lot of mobility when looking for and hunting its prey (It can hunt in the larval or adult stage). They have different types of oral apparatus (chewing or mincing-suction). An example of this type of insects are ladybugs, hoverflies, lacewings or spiders .

However, when we speak of parasitoid insects , as in the case of Trichogramma, we refer to a group of insects that lay their eggs inside ( endoparasitoids ) or outside ( ectoparasitoids ) of an organism. These eggs will develop in a larval state inside the body, consuming its reserves and causing death. Many species of hymenoptera are parasitoids of garden aphids or caterpillars. They can also parasitize the eggs laid by insects, as in the case of Trichogramma .

What is Trichogramma?

Within the Hymenoptera group (where wasps, bees or ants are) there are many different families. One of them is the Trichogrammatidae family, where the Trichogramma genus is found. This genus is made up of small parasitoid wasps of insect eggs and sometimes smaller than 1 millimeter. There can be more than 200 different species!

How can you eliminate Trichogramma pests?

As we have seen previously, these small beneficial wasps will look for where the insects in the garden lay their eggs and, once located, they will carry out the laying inside these eggs . The larvae will develop Trichogramma inside these eggs , killing the embryos inside.

Once the larval stage and the nymphotic stage have finished, the little wasp will come out of the egg making a small hole . We can differentiate the eggs that have been parasitized by these wasps as they turn black.

There are some species of Trichogramma that can parasitize more than 100 eggs throughout their life and normally act between the months of May to August.

Against what type of pests is Trichogramma used?

Trichogramma can attack many types of insects , including those that are problematic in the garden. However, their favorite species are the eggs of Lepidoptera, such as the corn borer, the apple carpocapsa or the cotton worm. 

Corn borer (Ostrinia nobilalis)

It could be said that the corn borer is one of the most important pests in this crop. These caterpillars damage the ears and stalks of corn by tunneling into them to feed.

Apple Carpocapsa (Cydia pomonella)

Carpocapsa can become a very harmful pest for our apple trees. Winters as a caterpillar in trunk grooves and tree branches. They can dig galleries inside the fruit. The optimal conditions for mating are sunsets, a temperature greater than 15ºC. During the day, the adults are immobile in the trees.

Cotton worm (Helicoverpa zea)

As in the previous cases, the cotton worm can cause serious damage in agriculture. In this case, the larvae attack the cotton crop but there are other species of the same genus such as Helicoverpa armigera that can attack tomato, corn, etc.

How to apply the Trichogramma product?

In stores you can find different products with this name and different application methods. For example, in capsules or in small cartons that are hung on the plants. They can be distributed manually or with more technical methods such as drones. Regarding the conditions and time of application, you will find all the information in the container.

Here you can see an example of an open capsule in which there are Trichogramma wasps.

As in most biological control methods, you can complement the use of these beneficial wasps with others such as  Bacillus thuringiensis.

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