Commercial‐scale field performance of aerially applied Trichogramma spp. against Ostrinia nubilalis

Applying Trichogramma spp. against Ostrinia nubilalis in the protection of maize crops has been tested, used in practice and discussed for years. Despite the evidence of satisfactory protection levels, this form of pest control has not been widely adopted in many countries yet. This paper presents results of an observational study on the effects of augmentative releases of this egg parasitoid using a gyroplane‐mounted spreading system in commercial‐scale fields. The effects were observed over eight seasons in large maize fields in a number of locations in Poland. In all cases, the share of plants showing signs of O. nubilalis larval feeding, as well as the average number of damages per plant, were significantly lower in protected fields compared with control fields: the relative reduction was, correspondingly, 0.643 (95% confidence interval, CI [0.602, 0.685]) and 0.731 (95% CI [0.702, 0.760]). Considering the benefits of aerial application (low labor intensity, prompt reaction to the pest outbreak, short time of application over large areas typical for maize plantations, avoiding soil compaction typical for using wheeled spreaders), this method of applying Trichogramma appears a rational choice.