Distribution of psocids (Psocoptera) in temperature gradients in stored wheat

Abstract

a b s t r a c tPsocids have become important pests of stored products during the last two decades, but little is known about their behavior or ecology. We examined distribution of Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), and Liposcelis paeta (Pearman), three of the main psocid pests of stored grain throughout the grain growing regions of the world, in temperature gradients of 20 e24 C, 20 e30 C, and 20 e42 C in small bulks of wheat to determine their ecological preferences. Psocids consistently preferred the warmest regions of the gradients, except in the 20e42 C gradients. Over 80 and 78% of psocids moved to the warmest region of the grain in the 20 e24 and 20 e30 gradients, respectively. Liposcelis bostrychophila females and both sexes of L. paeta preferred the warmer region of the grain in the 20 e42 gradient, while densities of L. entomophila males were higher in more moderate temperature regions of the grain and densities of L. entomophila females were evenly split between the warm and hot regions of the grain. Temperatures can be below 20 C during much of the storage season for grains, so the current results help to explain why psocids move to warmer regions of the grain which occur toward the center of the grain mass as grain temperatures cool in the fall. This may allow psocid populations to continue to grow during the colder months.Published by Elsevier Ltd.

Distribution of three psocid species (Psocoptera: Liposcelididae) in different moisture gradients in wheat

“…Different temperatures and moisture contents in wheat create different relative humidities. This may impact their movement and preferred location in grain stored in bins or in different temperature (Throne and Flinn, 2013) and moisture gradients as demonstrated in this study. This research shows how psocids respond to different moisture gradients in grain, which can help to improve sampling methods and to make better pest management decisions.…”

“…The distribution of psocids in different moisture gradients was determined using a circular metal arena (60 cm in diameter by 9 cm in height) Hagstrum, 1998, 2011). The arena was insulated with an attached base and a removable lid (2 cm thick wood and 3.5 cm thick insulating foam on the outside) (Throne and Flinn, 2013). The arena had a removable metal divider that partitioned it into three rings (outer, middle, and inner).…”

“…Therefore, we tested three different moisture gradients (11e12e13%, 11e13e15% and 13e14e15%) for L. bostrychophila females, and for females and males of L. entomophila and L. brunnea; and a control (13e13e13%) for females and males of L. brunnea. The control data for L. bostrychophila females, and for females and males of L. entomophila was taken from a previous study (Throne and Flinn, 2013) that was conducted with the same environmental conditions used in this study. The moisture content of wheat was measured using a grain moisture tester (GAC2000, DICKEY-john Co., Auburn, IL).…”

“…They also found that psocids were more abundant during the fall at the center of the bin where temperature and grain moisture content were higher that in other parts of the bin. Subsequently, Throne and Flinn (2013), using a 60-cm-diameter circular arena, studied the distribution of Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), and Liposcelis paeta (Pearman) in three different temperature gradients (20e24 C, 20e30 C, and 20e42 C). They found that in general the three psocid species moved to the warmest region of the grain in the three gradients with the exception of the 20e42 C temperature gradient where L. entomophila males preferred moderate temperatures and L. entomophila females were evenly distributed between the two warmest regions of the grain.…”

Evaluation of light attraction for the stored-product psocid, Liposcelis bostrychophila

“…Opit et al (2009) observed that populations of psocids in steel bins were more abundant at the center of the bin during the fall where temperature and grain moisture content were higher that in other parts of the bin. In laboratory tests, L. bostrychophila responded to temperature gradients (Throne and Flinn 2013) and moisture gradients (Diaz-Montano et al 2014a), with a preference for the warmest and highest moisture regions. However, how stored-product psocids respond to light conditions has not been investigated.…”