2020 Volume 62 Pages 121-132
Two predatory bugs, Orius strigicollis (Poppius) and Nesidiocoris tenuis (Reuter), are indigenous natural enemies against thrips. We evaluated effective insectary plants for the conservation of these predators in open fields. We investigated the population dynamics of thrips and predators on 10 plants in 2016 (from summer to fall season) and 13 plants in 2017 (from spring to summer season), including French marigold Tagetes patula, sweet basil Ocimum basilicum, holy basil O. tenuiflorum, buckwheat Fagopyrum esculentum, and okra Abelmoschus esculentus. Population dynamics of O. strigicollis were significantly affected by the density of thrips; however, the relationship between the level of prey-predator densities on each plant was not completely proportional. As the suitability of supplementary foods (pollen or nectar) for O. strigicollis is known to differ among plants, we hypothesized that the qualities of flowers as foods might also affect the predators’ population density. On the other hand, the correlation between the population dynamics of N. tenuis and thrips was mutually unrelated, suggesting that occurrence of N. tenuis depends on plant species. The effective insectary plants in this study were buckwheat for O. strigicollis and garden verbena Verbena × hybrida ‘Hanatemari-Aya’ or holy basil for N. tenuis.
