Sequential Controlled Atmosphere Treatments for Quarantine Control of Pacific Spider Mites (Acari: Tetranychidae)

Abstract

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% CO 2 for 1, 2, or 3 d at 0°C were followed by an 18-d treatment at 0°C with air, 8% CO 2 in air, or 20% CO 2 /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% CO 2 + 18 d of 20% CO 2 /5% O 2 , 2 d of 80% CO 2 + 18 d of 8% CO 2 in air (19% O 2 ), and 3 d of 95% CO 2 + 18 d of air resulted in complete mortality of larvae, protonymphs, deutonymphs, and adults. These 3 sequential treatment combinations show potential for use as quarantine treatments. We hypothesize that the physiological damage to arthropods caused by a shock treatment cannot be repaired when the shock treatment is followed by a long-term mild treatment; rather, the damage is deepened gradually to an irreversible level at which the arthropods die.