A Novel Trichogramma ostriniae Release System to Control Ostrinia nubilalis in Sweet Corn

Highlights A first novel injection system was built for spraying Trichogramma at a large scale in sweet corn fields. A mechanical mixer was designed for a rapid dissolution of xanthan and guar gums. The injection system achieved a Trichogramma emergence rate efficiency of 83%. Hose drops addition resulted in an extra 44% spraying coverage underneath sweet corn leaves. Abstract. In sweet corn processing sector, the use of Trichogramma for controlling Ostrinia nubilalis is uncommon in fields, primarily due to the absence of efficient mechanical deployment tools. The poor dissolution of xanthan and guar gums and the medium released along with Trichogramma also impedes the deployment of this biocontrol method. Thus, the preparation of the spraying solution and its application needed to be optimized to be feasible and profitable at a large scale. This work aimed to spray Trichogramma pupae by creating a novel tool: a specific mechanical mixer designed for the rapid dissolution of gums and a modular injection system containing a mixture of Trichogramma pupae and gum formulation to improve the Trichogramma spraying efficiency. Trichogramma emergence rate and concentration were assessed. Results showed that this spraying system greatly facilitated the release of Trichogramma ostriniae and the dissolution of xanthan and guar gums. Specifically, a 4-blade serrated dispersion disk dissolved 16 L at 12 g/L of gum in less than 6 minutes. The injection system successfully distributed pupae through both sides of the sprayer boom with an overall emergence rate efficacy of 83%. Also, an additional 44% of spraying coverage was achieved by spraying under sweet corn leaves using hose drops. Combined with the easy installation on any commercial sprayer, this modular injection system represents a promising pest control tool in organic and conventional crops. Keywords: Injection, Mechanized release, Ostrinia nubilalis, Spraying, Sweet corn, Trichogramma.