DESIGN AND TESTING OF A BOOM SPRAYER PROTOTYPE TO RELEASE TRICHOGRAMMA OSTRINIAE (HYMENOPTERA: TRICHOGRAMMATIDAE) IN SWEET CORN FOR BIOCONTROL OF OSTRINIA NUBILALIS (HUBNER) (LEPIDOPTERA: CRAMBIDAE)

Sweet corn requires many insecticide applications to control its main pest: the European corn borer (Ostrinia nubilalis) (Lepidoptera: Crambidae). The use of Trichogramma is an effective biological alternative to control the European corn borer in sweet corn. However, manual introduction at large scale of Trichogramma using Trichocards is time-consuming. Mechanized infroduction of Trichogramma using a boom sprayer is an innovative and advantageous solution. The objective of this study was to design and test a boom sprayer to spray Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) in sweet corn canopy under real field conditions. Trichogramma ostriniae parasitized eggs were sprayed at a rate of 800,000 individuals ha(-1) using a boom sprayer designed at the Department of Soils and Agri-Food Engineering of Universite Laval, Quebec, Canada. Trichogramma parasitized eggs were also introduced at a rate of 500,000 individuals ha(-1) using Trichocards. Overall, eight releases were made during the 2016 season. Field trial results showed a 17.22% emergence rate reduction of Trichogramma in the sprayed plots compared to Trichocards. Total fecundity and longevity of sprayed T. ostriniae females were not negatively affected by spraying; indicating that spraying did not have any negative impact on their quality. The parasitism rates observed on natural egg masses of O. nubilalis and on sentinel egg masses of Ephestia kuehniella were comparable for both methods. At harvest, sprayed and Trichocards treatments resulted in adequate control of the European corn borer. Obtained results also showed that spraying was 1.7 times faster than the manual infroduction of Trichocards. Overall, the results indicate that spraying is a promising technique for an efficient and viable infroduction of Trichogramma parasitized eggs. However, more research is recommended to further optimize the spraying parameters. The spraying system successfully used in sweet corn could also be used in corn production and adapted to other crops such as pepper, beans, and potatoes to control the European corn borer.