A study of relationships of four insects to heating in stored grain Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8910jw888

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  • This study was conducted to determine the effects of insect infestation on areas of heating in stored grain, and to demonstrate the ability of four species of insects to initiate or promote the spread of these heating areas. The four insects used were the granary weevil Sitophilus granarius (L.), the lesser grain borer Rhizopertha dominica (F.), the saw-toothed grain beetle Oryzaephilus surinamensis (L.), and the red flour beetle Tribolium castaneum (Hbst.). All four of these insects are common pests of stored grain. Heating was initiated by adding moisture to a small portion of a confined mass of wheat. The term hot spot was used in reference to areas of the grain mass that showed a rise in temperature above that of the surrounding grain. Hot spots due to the growth of fungi on the moistened grain were referred to as fungus hot spots. A device was designed and constructed in which a small hot spot could be started and observed visually and electronically. It consisted of a wooden box of about one cubic foot capacity with two glass sides and an internal system of thermocouples and humidity indicators. Ten of these boxes were in operation during a period of two years in 18 laboratory experiments. A larger system of thermocouples and humidity indicators was installed in a Butler bin at the Oregon State University Entomology Farm in which 600 bushels of wheat were utilized in four different experiments. Hard white wheat was used in all experiments, and test insects were obtained from laboratory cultures. It was observed that fungus hot spots reached a peak of heating at room temperature about two weeks after moisture was added. Heating was confined to the small mass of grain that was moistened by the addition of water when no insects were present, and did not spread to the surrounding grain mass. The temperature declined rapidly unless additional moisture was forced into adjacent areas of the grain mass to start a second area of heating. Effects of insects on fungus hot spots varied according to the species of insect present. The granary weevil demonstrated the greatest ability, of the four insects tested, to promote the spread of a fungus hot spot. Hot spots involving the granary weevil, either by itself or in combination with other insects, expanded until most of the wheat in the laboratory boxes was involved. The lesser grain borer demonstrated an ability to promote the spread of a fungus hot spot almost equal to that of the granary weevil, but required a longer period of time. The red flour beetle and the saw-toothed grain beetle failed to promote the spread of a fungus hot spot, and heating declined as rapidly in their presence as without them. Field experiments on a larger scale likewise showed the granary weevil to be superior to the saw-toothed grain beetle in promoting the spread of fungus hot spots. Higher temperatures were recorded in the field experiments than in the laboratory experiments but heating was confined to the small mass of moistened grain when granary weevils were not present.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2014-05-08T17:18:04Z (GMT) No. of bitstreams: 1 EighmeLloydE1966.pdf: 2845884 bytes, checksum: 6f5a73dc6657d525dfd9c33118b06361 (MD5)
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