Robert R. Cogburn

Susceptibility of varieties of stored rough rice to losses caused by storage insects.

Abstract Losses caused by Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Sitotroga cerealella (Olivier) in 6 commercial varieties of rough rice from the Southern United States were assessed as weight loss of rough rice, loss of milling yield, and loss of monetary value. Over 3 insect generations, S. oryzae caused the least damage, probably because this species requires grains with gross hull defects and the proportion of such grains was relatively small. Damage attributable to S. cerealella or R. dominica was approximately equal. The varieties Vista and Lebonnet were the most susceptible and the variety Dawn the most resistant after 3 generations.

A method of dosimetry for a bulk-grain irradiator

Abstract This paper discusses the advantages of a lithium fluoride thermoluminescent dosimetry system for use in a bulk-grain irradiator. Unique problems of dosimetry exist because dosimeters must be mixed with the grain, must have the same flow characteristics as the grain and must have adequate resistance to breakage. Tests proved that encapsulated LiF dosimeters provide an accurate record of absorbed dose in a mass of wheat treated by a bulk-grain irradiator. Variations in dosage revealed by the dosimeters showed satisfactory treatment of the majority of the wheat, with overexposure of a small percentage.

World collection rice varieties: Resistance to seed penetration by Sitotroga cerealella (Olivier) (Lepidoptera, Gelechiidae)

Abstract Lots of 200 eggs of Sitotroga cerealella (Olivier) were placed on 10 g samples of 780 varieties of rice from the U.S.D.A. World Collection. An average of 91% of the eggs hatched and between 1 and 83% of the larvae from these reached the adult stage and emerged. Less than 10% survived in 102 varieties. Graphic data exhibit a bimodal shape, indicating that two resistance bases operated against these insects; both apparently acted to prevent kernel entry by the freshly hatched larvae.

Survival and development of Sitotroga cerealella (Oliv.) on seeds from species of Oryza other than Oryza sativa L

Abstract Fifty accessions of wild Oryza spp (those other than Oryza sativa L.) were acquired and grown in pots to increase the seed. Physical and chemical characteristics of the seed were measured. The amylose content of most of the species of wild Oryza was high (>23%) but all were within the range required for cultivated rice. Gelatinization temperatures also were within required ranges. Therefore, should any of these Oryza spp possess insect or disease resistance, general hardiness, cold-tolerance or other characteristics desirable for new varieties of rice, the transfer may be made easier because the cooking quality characteristics (amylose and gelatiniziation temperature type) of these species, being within ranges common in commercial varieties of rice, would not require alteration. Resistance or susceptibility to Sitotroga cerealella (Oliver) was tested in the wild Oryza spp and in three varieties of rice. Survival and developmental time from larvae to adult were the criteria used to assess resistance/ susceptibility. Insect performance was adversely affected by intact hulls and small seed size. The hull character in wild Oryza is no stronger than that previously observed in rice and small seed size is not a viable option as a resistant base. A resistant character for S. cerealella that would justify an attempt to transfer the trait from one species to another apparently is not available in the accessions of wild Oryza that were tested.

Effects of Irradiated Diets on Production of Progeny by Several Successive Generations of the Indian-Meal Moth, Plodia interpunctella (Hübner)

Indian meal moths, Plodia interpunctella, were reared for nine generations on an irradiated whole wheat flour diet or for four generations on irradiated raisins. Diets were treated with dosages of 0, 25, 50, 100, 500, 1000, and 4300 krad of gamma radiation. Each generation was checked for fecundity and for altered sex ratios. No statistically or biologically significant effects on the numbers of progeny or their sex ratio were found. Irradiated flour and raisins appear to be safe as insect culture media.