Predatory Efficacy of the Black Ladybird Beetle, Stethorus sp. against the Two-spotted Red Spider Mite, Tetranychus urticae Koch on Rose Plants

The black ladybird beetle, Stethorus sp. is a generalist predator whose larvae and adult prey on all developmental stages of the two-spotted red spider mite, Tetranychus urticae Koch. In order to develop a bological control program of T. urticae in the Mekong Delta of Vietnam, the predaotry efficacy of Stethorus sp. on T. urticae had been investigated.

The investigation was conducted under the laboratory and net-house conditions at the College of Agriculture, Can Tho University.

Under laboratory conditions, fourth instar larvae exhibited the highest predation rate, while second instar larvae showed the lowest. Second instar larvae consumed an average of 65.63 eggs, 26.13 larvae, or 22.38 adults per day. In contrast, fourth instar larvae consumed 183.63 eggs, 88.63 larvae, or 73.63 adults per day. Adult female beetles consumed 149.38 eggs, 75.63 larvae, or 46.5 adults per day, while adult males showed lower consumption rates of 88 eggs, 62.25 larvae, or 36.13 adults per day. Under net house conditions, one pair of black ladybird beetles provided optimal control of the two-spotted red spider mites at a density of 56 mites per plant, with a control efficacy of 97.07 per cent at 5 days post-release. At a red spider mite density of 168 individuals per plant, 4 and 6 pairs of black ladybird beetles demonstrated superior control efficacy of 93.02 per cent and 99.54 per cent respectively at 5 days post-release.