Effects of Dehumidification on the Survivorship of Four Psocid Species

Psocids are damaging stored-product pests. In this study, eggs and early-instar nymphs, adults, and all life stages of Liposcelis entomophila, L. decolor, L. bostrychophila, and L. paeta were subjected to 43, 50, or 75% (Control) relative humidity (RH) for 2, 4, 6, 8, 10, 12, 14, or 16 d at 30.0°C. All adults of these species died within 8 d at both 43 and 50% RH, except for L. bostrychophila, which required 12 d at 50% RH for 100% mortality to occur. For all life stages and eggs and early-instar nymphs, maximum survival times (times to 100% mortality) at 43 or 50% RH for L. entomophila, L. decolor, L. bostrychophila, and L. paeta, were 8 and 10 d, 8 and 12 d, 12 and 14 d, and 12 and 16 d, respectively. During this study, numbers of nymphs and adults of all species 14 d after the RH treatments increased within the 75% RH Control arenas. Different species and life stages responded differently to 43 and 50% RH, as time to kill all stages of the four psocid species was 8-12 and 10-16 d, respectively. Results indicate that using a specific RH environment may be effective in psocid management.