Efficacy of carbon dioxide treatments for the control of the two-spotted spider mite, Tetranychus urticae, and treatment impact on plant seedlings.

To develop a new control method for the two-spotted spider mite (TSSM), Tetranychus urticae, we investigated the effect of controlled atmospheres of carbon dioxide (CO) on TSSM mortality under different concentrations and treatment periods, and evaluated the impact of treatments on seedlings of five host plants of TSSM. Egg hatching rate of TSSM was reduced to 37.7, 5.4 or 0% after 24 h treatment involving concentrations of 16.7, 33.3 or 50%, respectively. Mobile stages (nymphs and adult) of TSSM were completely controlled after 24 h treatment at concentrations higher than 33.3%. After 4 h at concentrations of 33.3 or 50%, 1st-day survival rate for all mobile stages was 45.3 or 36.0%, respectively, whereas after 8 or 16 h treatments, all values were decreased to zero. Seedlings of four major host plants of TSSM (cucumber, eggplant, rape, green peppers) were damaged to varying degrees after 24 h at the three concentrations, but strawberry, another host plant, was not damaged. Cucumber suffered the most serious damage, resulting in wilting and death. In conclusion, controlled atmospheres of CO can kill TSSM, particularly at high concentrations and with long treatment times. It can be used to control TSSM on strawberry, but should be used cautiously on other host plants.