Effects of Carbon Dioxide Enrichment on Leaf Chemistry and Reproduction by Twospotted Spider Mites (Acari: Tetranychidae) on White Clover

Plant growth and yield responses to carbon dioxide (CO2) enrichment are well es- tablished. Much less is known of the response of arthropod pests to CO2 enrichment. Reproductive response of twospotted spider mites (Tetranychus urticae Koch) on white clover (Trifolium repens L.) to a range of CO2 concentrations was measured. The CO2 treatments were applied for 24 h d 1 at395, 484, 570, 657, and 748 LL 1 on the 14 d before and 26 Ð27 d after infestation with mites. Eggs, larvae, nymphs, and adult mites were removed from leaves and counted 27Ð29 d after infestation. Leaf area and weight were measured, and leaves were analyzed to measure structural and nonstructural carbohydrates, N, amino acids and digestibility. Carbon dioxide enrichment caused linear increases in plant growth and foliar nonstructural carbohydrates, but caused linear decreases in foliar N. Carbon dioxide enrichment signiÞcantly increased the rate of mite reproduction on both clover clones. Correlations between mite population increase were signiÞcantly positive for foliar nonstructural carbohydrates and signiÞcantly negative for foliar N. Concentrations of ambient CO2 expected in the 21st century may increase the risk of mite population damage on some plant species.