Keywords: rs p in cide e co stor mag iffu measurable barrier to oxygen penetration into the container. e (PICS iners fo alpers oleop dock e ed of t polypropylene bag (Baoua et al., 2012; Murdock et al., 2012; cease feeding, growing and developing and often die (Murdock et al., 2012). Population growth is thereby arrested. If the technology is applied early in the storage season, it results inminimal or no damage to the grain (Murdock et al., 2012; Cheng et al., 2012;
Baoua et al., 2013a). in that as well as in the testa (Baoua et al., 2012). llow insect devele due to the influx imately lead to an . However, if the ., if only the inner t, this intact layer l development and damage near the hole. If there are multiple holes in an HDPE liner instead of just one, one would expect increased numbers of insects to develop. In that case, one would expect a positive relationship between the number of holes in the HDPE film and the number of insects that develop.
Insects often aggregate at the top of grain stores (Navarro et al., 1984; Driscoll et al., 2000) and unpublished field observations of the PICS technology sometimes noted large numbers of insects gathered at the top of PICS bags (Baoua, personal communication). * Corresponding author
Contents lists availab
Journal of Stored P .e
Journal of Stored Products Research 62 (2015) 40e45E-mail address: email@example.com (L.L. Murdock).Baributsa et al., 2013). The two inner bags are 80 mm thick. The
HDPE layers, while not perfectly impermeable, greatly inhibit O2 and CO2 exchange between the air spaces within the bags and the atmosphere (Kjeldsen,1993). Metabolism of insects already present in the grainwhen it is put into the bag leads to much lower internal levels of O2 and higher levels of CO2. With reduced available O2 (hypoxia) and elevated CO2 (hypercarbia), the insects in the grain
Holes in the HDPE liners of PICS bags may a opment to occur in the grain adjacent to the hol of O2 diffusing through the opening. This can ult increased level of damage in the stored grain second, outer layer of HDPE were still intact, i.e layer has been penetrated by an emerging insec may sufficiently retard O2 influx to prevent larvahigh density polyethylene (HDPE) liners nested inside a woven on through the plastic membrane, making a round emergence holeCallosobruchus maculatus
Storage 1. Introduction
The Purdue Improved Crop Storag to provide affordable hermetic conta cowpea grain, Vigna unguiculata (W
Callosobruchus maculatus Fabricius (C the Sahel region of West Africa (Mur et al., 2011). Each PICS bag is comprishttp://dx.doi.org/10.1016/j.jspr.2015.03.005 0022-474X/© 2015 Published by Elsevier Ltd.© 2015 Published by Elsevier Ltd. ) systemwas developed r weevil-safe storage of ), against the bruchid, tera: Chrysomelidae) in t al., 2003, 2012; Sanon hree separate bags, two
PICS HDPE liners sometimes acquire small holes during storage, most frequently in the inner liner (Baoua et al., 2012). Cases in which both HDPE layers have been penetrated by insects have also been observed but are much less frequent. Holes in the HDPE film often result when an infested seed with a pupal cell happens to be pressed against the inner HDPE membrane under the pressure exerted by the bulk grain in the bag.When the adult leaves its pupal cell it cuts its emergence hole through the seed testa and continuesCowpea
PostharvestHermetic with a single layer of HDPE film, grain damage was indistinguishable from that seen under full hermetic conditions. We provide evidence that a single layer of woven polypropylene contributes a small butThe effect of small leaks, grain bulk, and performance of hermetic storage
D.T. Martin, S.B. Williams, D. Baributsa, L.L. Murdo
Department of Entomology, Purdue University, 901 West State Street, West Lafayette, IN a r t i c l e i n f o
Received 22 August 2014
Received in revised form 19 March 2015
Accepted 19 March 2015
Available online a b s t r a c t
Hermetic storage containe damage and ultimately sto created by insects or by ac
Using cowpea grain and th which holes in a hermetic numbers of holes, seed da uted a barrier to oxygen d journal homepage: wwwhe patching of leaks on the 907, USA are often used by farmers to protect their harvested grain from insect sect population development. Sometimes holes in a storage container are nt; such holes may reduce the effectiveness of the hermetic storage unit. wpea bruchid, Callosobruchus maculatus (F), we investigated the degree to age container wall affect the level of grain damage. When there were low e increased markedly with each additional hole. The grain itself contribsion through the grain mass. If holes in the container wall were patched le at ScienceDirect roducts Research lsevier .com/locate/ jspr d PrThis increased insect density may be a result of higher oxygen availability at the top of the bags or may merely reflect an escape behavior of the insects. Oxygen availability may be at its lowest toward the center of the grain mass due to (1) slow diffusion rates through the grain (Singh et al., 1984; Shunmugam et al., 2005;
Huang et al., 2013; Haugh and Isaacs, 1967) and (2) oxygen use by insects closer to the outer perimeter. Packing grain tightly, decreasing temperature, and increasing moisture content will further reduce oxygen availability within the center of the grain mass (Singh et al., 1984; Driscoll et al., 2000; Shunmugam et al., 2005).
Differences in O2 concentration at points within PICS bags may occur and influence insect metabolism and development. Such differences may depend on the location of infested seeds within the container. If more oxygen were available in a particular region of the grainmass (likely toward the surface of the grain mass or near a hole) more damage might occur. In an earlier study, insect populations near an air inlet developed at a faster rate than those further from the inlet (Driscoll et al., 2000). Less damage is likely farther from the surface of a bulk or more distant from holes and imperfections in the container walls.