Deterrence of oviposition of adult Ostrinia nubilalis Hubner (Lepidoptera: Pyralidae) by a natural enemy food supplement Envirofeast on maize in France

Oviposition deterrent activity of a natural enemy food supplement, Envirofeast, against Ostrinia nubilalis Hubner females was studied in choice and no-choice tests under laboratory conditions. Maize plants treated with Envirofeast at 25-40 g a.i./l had significantly fewer egg masses per leaf and eggs per egg mass laid on them compared with the untreated control plants in both choice and no-choice tests. However, maize plants treated with Envirofeast concentrations of 10-20 g a.i./l did not significantly deter the insect's oviposition. The optimum rate at which Envirofeast could deter oviposition was 25 g a.i./l. Increasing the rate of Envirofeast application from 25 g to 40 g a.i./l did not significantly increase its oviposition deterrent activity against O. nubilalis. However, reducing the rate from 25 to 20 g a.i./l resulted in a significant reduction in the oviposition deterrent activity of Envirofeast. The egg masses laid by O. nubilalis on Envirofeast treated plants were essentially (80%) located on the lower leaf surfaces in contrast to untreated (control) plants where only 40-60% of the egg masses were deposited on the lower leaf surfaces. The egg masses on the Envirofeast-treated plants were found at sites which did not receive sprays, indicating the importance of good spray coverage when the product is used in the field. The study has demonstrated the oviposition deterrent activity of Envirofeast against O. nubilalis on maize and this indicates that Envirofeast may have the potential to be integrated into programmes to assist in the control of O. nubilalis on maize.