Sequential controlled atmosphere treatments for quarantine control of Pacific spider mites (Acari : Tetranychidae)

The effect of sequential controlled atmosphere treatments on the mortality of Pacific spider mites, Tetranychus pacificus McGregor, was investigated. Shock treatments with 65, 80, or 95% CO2 for 1, 2, or 3 d at 0 degrees C we re followed by an 18-d treatment at 0 degrees C with air, 8% CO2 in air, or 20% CO2/5% O-2. Synergistic effects on arthropod mortality were generated by the combination of shock and follow-up treatments. Sequential treatment combinations of 1 d of 80% CO2 + 18 d of 20% CO2/5% O-2, 2 d of 80% CO2 + 1 8 d of 8% CO2 in air (19% O-2), and 3 d of 95% CO2 + 18 d of air resulted i n complete mortality of larvae, protonymphs, deutonymphs, and adults. These 3 sequential treatment combinations show potential for use as quarantine t reatments. We hypothesize that the physiological damage to arthropods cause d by a shock treatment cannot be repaired when the shock treatment is follo wed by a long-term mild treatment; rather, the damage is deepened gradually to an irreversible lever at which the arthropods die.