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

Authors: Throne, James; Flinn, Paul

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2013
Publication Date: 8/5/2013
Publication URL: http://handle.nal.usda.gov/10113/57835
Citation: Throne, J.E., Flinn, P.W. 2013. Distribution of psocids (Psocoptera) in temperature gradients in stored wheat. Journal of Stored Products Research. 55:27-31. DOI: http://dx.doi.org/10.1016/j.jspr.2013.07.003.

Interpretive Summary: Psocids (insects which are also called booklice) are pests of stored grains in most of the world, but little is known about their behavior or ecology. We examined distribution of three of the main psocid pests of stored grain in temperature gradients in small bulks of wheat to determine their ecological preferences. Few psocids were found in the coolest region of the grain, which was at 68 degrees F. Psocids consistently preferred the warmest regions of the gradients, except when the high temperatures reached 108 degrees F. Females of Liposcelis bostrychophila and both sexes of L. paeta still preferred this warmest region of the grain, but not L. entomophila males and L. entomophila females were evenly split between the warm and hot regions of the grain. Temperatures can be below 68 degrees F. 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. Knowing how different species of psocids respond to temperature gradients in grain may help us improve sampling and management methods for psocids as the temperatures in a grain mass change throughout the year.

Technical Abstract: Psocids 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), L. entomophila (Enderlein), and L. paeta (Pearman), three of the main psocid pests of stored grain throughout the grain growing regions of the world, in temperature gradients of 20°-24°C, 20°-30°C, and 20°-42°C in small bulks of wheat to determine their ecological preferences. Psocids consistently preferred the warmest regions of the gradients, except in the 20-42°C gradients. Over 80 and 78% of psocids moved to the warmest region of the grain in the 20°-24° and 20°-30° gradients, respectively. L. bostrychophila females and both sexes of L. paeta preferred the warmer region of the grain in the 20°-42° 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.