Effect of Fumigation of High Concentration Carbon Dioxide on Two Spotted Spider Mite , Tetranychus urticae Koch (Acari: Tetranychidae) and Strawberry Runner Plant

Two spotted spider mites, Tetranychus urticae Koch the most important pests of strawberry, have developed resistance to chemical pesticides. We investigated the effects of high carbon dioxide atmospheres on two-spotted spider mites and strawberry plants just before transplanting. Percent mortality of adult female mites, young eggs (24h after laying), and old eggs (48-72h) exposed to 60% CO2 at different temperatures (25, 30, and 35 degrees C) was evaluated over time. Mortality of all spider mite stages increased with exposure duration at each temperature, and the time required to achieve 100% mortality decreased as temperature increased. Exposure to 60% CO2 at 30 degrees C for 16h was 100% lethal to every developmental stage tested. Furthermore, 24h of 60% CO2 treatment did not induce external damage or adversely affect flowering of the primary flower clusters on strawberry plants. In a large-scale test of elevated-CO2 atmospheres, the two spotted spider mite population was greatly suppressed relative to untreated fields, and strawberry plants remained healthy. Thus, our findings suggested that CO2 treatment could be used to propagate spider-mite-free plants in strawberry nurseries and enhance strawberry integrated pest management systems.