Evaluation of Stratiolaelaos scimitus and Neoseiulus barkeri for biological control of thrips on greenhouse cucumbers

Stratiolaelaos scimitus Berlese (Acari: Laelapidae) is an important soil-dwelling predatory mite used to control thrips and it is necessary to explore its potential predation capacity. In the present study, the functional response for S. scimitus on the pupae of Frankliniella occidentalis Pergande was examined. In addition, the effects of released S. scimitus for the control of Thrips tabaci Lindeman and F. occidentalis on greenhouse cucumber were evaluated, and compared with that of the common predator Neoseiulus barkeri Hughes (Acari: Phytoseiidae). The results showed that S. scimitus exhibited a Holling type II functional response on thrips pupae. The greenhouse study indicated that the release of N. barkeri and S. scimitus separately at the density of 250 mites/m² suppressed the population growth of thrips. In comparison with control plots, N. barkeri and S. scimitus reduced the population of T. tabaci by 76% and 64% in six weeks, respectively. Releases of N. barkeri and S. scimitus led to a reduction in F. occidentalis by 41% and 43%, respectively. Significantly lower densities of both thrips species per leaf were recorded in treatments of individual releases of N. barkeri or S. scimitus than that in the control plots. The findings highlight the potential for utilising N. barkeri and S. scimitus as biological control agents of T. tabaci and F. occidentalis, respectively.