Effects of temperature, relative humidity, insect infestation, and phosphine fumigation on the germination, vigor, and storage quality of hard white winter wheat

Two varieties of hard white winter (HWW) and three varieties of hard red winter (HRW) wheat (1992 crop), collected from three locations in Kansas and one in Wyoming, were used to investigate the comparative susceptibility of HWW to major stored-product insects. When adults of rice weevil, lesser grain borer, and red flour beetle were allowed to oviposit for 7 days in samples from the various locations, numbers of rice weevil progeny did not vary significantly among the HRW and HWW varieties, however, there was significant negative correlation with kernel hardness. Numbers of progeny of both lesser grain borer and red flour beetle differed significantly among varieties and classes with both species producing the most progeny on HWW wheat. There was also a significant negative correlation between numbers of progeny produced by both species and the time to 50% progeny emergence. Neither HWW or HRW varieties showed a significant attraction for lesser grain borers or rice weevils.;Equilibrium moisture contents (EMC) at eight relative humidities were used to develop adsorption isotherms for two varieties of HWW and seven varieties of HRW wheat. Significant differences were observed between varieties of HWW and HRW wheat but not between the two classes. The constant used in the Chung equation to calculate EMC of HRW can be used to predict the EMC of HWW wheat. The effect of time, temperature, and moisture content on seed quality indicated that two HRW varieties (Karl and Tam 107) maintained a higher germination than all other varieties during storage periods. At 85% RH and 25 or 30;Samples of Rio Blanco, a HWW variety, from 1992 and 1994 crops were fumigated in the laboratory with phosphine at different dosages, temperatures, moisture contents, and repeat treatments. The effect of these factors was determined on germination, vigor, and loss of phosphine from the gas phase. Loss of seed germination and vigor was observed when seeds were fumigated at high phosphine dosage, moisture content, temperature, and repeat fumigations. When measured by gas chromatography, a significantly greater loss of fumigant from the gas phase was observed at high temperature, moisture content, and dosage.