The use of Trichogramma ostriniae for biological control in semi-arid western Nebraska

Trichogramma ostriniae has been used successfully as a biological control agent of lepidopteran pests including the European corn borer (Ostrinia nubilalis), the Asian corn borer (O. furnacalis), and the sugarcane grey borer (Argyroploce schistaceana). Despite preferring grassy habitats, T. ostriniae has been used successfully in broadleaf crops such as potato and bell pepper. However, most studies were conducted in humid climates. In order to test the efficacy of T. ostriniae in a semi-arid environment, field trials were conducted in western Nebraska. We released 0.92 million T. ostriniae per hectare into the center of a corn field and a dry bean field near Ogallala, Nebraska which has a semi-arid climate. Dispersion and parasitism were monitored with yellow sticky cards and sentinel egg masses respectively at 36 locations surrounding a central release point. Sentinel egg masses consisted of commercially available O. nubilalis. Sentinel egg masses and yellow sticky cards were left in the field for three days and then brought back to the lab for analysis. T. ostriniae were able to disperse rapidly. However, parasitism was low in both crops (6 and 3% of O. nubilalis egg masses were parasitized in dry bean and corn, respectively). So, we conclude that it is unlikely that T. ostriniae will be an effective biological control agent in semi-arid environments like western Nebraska.