Biological control with parasitoids


Biological control is the use of beneficial organisms (predators, parasitoids…) to control insect pests in a way to maintain their population at an economically viable level for the farmer. Hymenopteran parasitoids are the most successful and most commonly used agents for biological control of insect pests in Europe. A parasitoid is an insect that lay eggs on or inside a host. The larvae that will emerge from these eggs will then grow up by eating the insect and killing him at the end of its development.

Their main advantages over other biological control agents lies in their ease of maintenance and their high host specificity. Our research group studies the behavior and ecology of Hymenopteran parasitoids to optimize their use in biological control. New procedures and techniques for mass rearing are developed in close collaboration with biological control companies (Viridaxis).

We currently have two projects on this topics. The first one on the mass rearing of Trichogramma sp., a parasitoid of lepidoptera eggs (TRICHOTECH) and a second one on the management of cacopsylla pyri, a pest in pear orchards (BIOPSYLLA).

1) trichotech

Our main model species are the minute wasps of the genus Trichogramma. This project is clearly the continuation of the project WBGREEN Insectech project since 2012. Under Insectech, the possibility of producing artificial medium for trichogram rearing on chitosan beads was analyzed. However, the specific objective of Insectech does not allow us to analyze other interesting ideas that could feed the results already achieved and the various aspects outlined. In 2014, we continued with the Trichotech project. Our goal is to establish a comprehensive roadmap of rearing Trichogramma by identifying key steps in terms of production, cost and risks and proposing alternatives in terms of alternative hosts, artificial medium, and optimal density to use. The deliverable will be a roadmap of a complete description of the steps to develop an economically viable rearing and producing quality individuals.

2) Biopsylla

Belgium is one of the main European producers of pears with 8921 hectares of orchards and 280 000 tonnes of pear fruits per year. Currently, the control of insect pests in pear orchard is mainly done by the use of chemical treatments.

The main pest in pear orchards psylla Cacopsylla pyri. It is a sucking insect capable of ingesting considerable quantities of sap, which will decrease the quality availble for the fruit formation and allow the transmission of a phytoplasma that can cause the death of the tree. Moreover, they reject a large part of the sugars ingested in the form of honeydew deposited on the fruits and the leaves, thus promoting the development of fungi. All this makes of C. pyri the first pest in pear cultivation.

At present, there is no biological control solution for psylla. We are particularly interested in the parasitoid Trechnites insidiosus, which is the most frequent parasitoid in pear orchard. The latter is very little studied because of its small size (adult = 1 mm), although it has several interesting characteristics for the biological control of the psylla, such as the ability to predate on C. pyri larvae.

The objective of this project is therefore to develop an alternative biological control method that could replace chemical treatments, by using parasitoid specialists of the psylla in pear orchards, and that have zero impact on the environment and economically profitable to the orchard growers compared to the use of insecticides.

Aphid parasitoid life cycle