Technical Feasibility of Spraying Trichogramma ostriniae Pupae to Control the European Corn Borer in Sweet Corn Crops

The European corn borer, (Hübner), is the major insect pest of sweet corn in the province of Quebec, Canada, and around the world. The presence of this pest results in substantial yield decreases and profit losses for farmers. Currently, chemical insecticides are the main method used to control this insect pest. Nevertheless, there are some interesting alternatives to chemicals for controlling the European corn borer, in particular the use of predator insects. Many research studies demonstrated the effectiveness of using wasps to successfully control the corn borer. However, this biocontrol method is more expensive and complex than chemical insecticides. The main objective of this research study was to investigate the technical feasibility of spraying pupae to facilitate the implementation of this method and reduce operating costs. For this purpose, many experimental trials using were carried out in the laboratory, with the objective of finding a suitable aqueous solution that both disperses the pupae in the sprayer tank and causes them to adhere to corn leaves once sprayed. A laboratory-scale spraying system was also designed and built to check the viability of T pupae after immersion in the spray solution and spraying. The viability of pupae was investigated further using a field prototype boom sprayer. The results showed that it is possible to spray pupae while preserving their physical integrity. In addition, a mixture of guar gum and xanthan gum was found to be the most suitable for the adhesion of pupae to corn leaves. The system overall decreased the emergence rate of Trichogramma by 10% to 15% which is considered acceptable by the authors. The success of this spraying technique for controlling the European corn borer in corn crops is highly valuable and could be generalized to other predator insects.