Comparison of the effectiveness of two methods for releasing Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) against Aphis gossypii Glover (Homoptera: Aphididae) on cucumbers in a greenhouse

Abstract

The control of Aphis gossypii on cucumbers was evaluated by releasing egg mass sheets or flightless adults of Harmonia axyridis. In experiment one, 1, 5 and 10 egg mass sheets per plant in each greenhouse were released only one time. The density of aphids in the greenhouses receiving egg mass sheets of H. axyridis was lower than that without the sheets. Within 5 days after release, the greenhouses receiving 5 egg mass sheets and 10 egg mass sheets per plant showed reduction of aphid densities to less than 1% of that without the sheets. In experiment 2, five egg mass sheets and 5 flightless adults per plant were released in each greenhouse three times at about one week intervals. The density of aphids in greenhouses receiving flightless adults showed fluctuations to a lower level than in the greenhouses receiving egg mass sheets.