Clyde M. Christensen

Molds in house dust, furniture stuffing, and in the air within homes

Abstract 1.1. The mold colonies isolated from 76 samples of house dust collected in homes in and near St. Paul and Minneapolis, Minnesota, in the winters of 1950 and 1951 to 1952 varied from less than 10,000 per gram to more than 3,000,000 per gram. with an average of 179,966 mold colonies per gram. 2.2. The number of bacteria from 14 samples of house dust ranged from 1,144,000 to 20,000,000 per gram, and averaged 10,700,000 per gram. 3.3. Molds and bacteria were present in some numbers in the samples of new furniture stuffing, and were present in considerably greater numbers in some used materials. 4.4. Foam rubber appears to be somewhat susceptible to invasion by molds, though to a lesser degree than certain fibers. Bacteria do not appear to be present in any considerable numbers in either new or used foam rubber. 5.5. The molds present in the air within homes may differ in both kind and numbers from those in the outdoor air at the same time. The number of viable mold spores (or other inoculum) in the air within homes may fluctuate sharply during a single day, apparently increasing when the amount of physical activity within the home increases.

Development of Plodia interpunctella (Hb.) (Lepidoptera, Phycitidae) on different varieties of corn at two levels of moisture

Abstract There were large differences in the number of Plodia interpunctella completing the life cycle from egg to adult on nine hybrid varieties of corn (maize) conditioned to 13·5 and 15·7 per cent m/c and held at 70 and 80 per cent r.h., respectively. These differences were significant statistically at the 1 per cent level, the poorest survival being only 12 per cent at 70 per cent r.h. and the highest 74·5 per cent. The mean developmental periods also varied significantly, from about 31 to 35 days at 70 per cent r.h. The percentage survival and the developmental period were negatively correlated. These differences were removed by milling the corn and supplying it as meal. Differences of size and fecundity of moths emerging from different corn varieties were not then significant. More moths emerged in a shorter period at the higher m/c on every variety. As a rule males tended to predominate but not to a significant extent.

The relationship between Plodia interpunctella (Hb.) (Lepidoptera, Phycitidae) and stored-grain fungi

Abstract The development of Plodia interpunctella, in shelled corn (maize) discouraged the growth of stored grain fungi, and slightly raised the moisture content of the infested corn. Mouldy corn, on the other hand, hindered the development of this insect. Fewer larvae reached the adult stage on mouldy corn and only after a prolonged developmental period; the adults produced were smaller in size and produced fewer eggs in their ovaries than those on mould-free corn. The more mouldy the corn the more it became unfavourable for the insect but this depended in part on the fungus species present. The relationship between this insect and the majority of stored grain fungi appeared to be antagonistic. An exceptional relationship was found with Aspergillus halophilicus, in plated cultures, which attracted the adult insect to lay its eggs and on this fungus larvae developed almost as normally as on mould-free corn.

Tests of different media for the collection and identification of air-borne saprophytic fungi

Abstract 1. 1. The experimental results to date indicate that Mehrlichs medium with 75 Gm. of sodium chloride per 1000 c.c. of H 2 O will give a significantly higher mold count per plate than the casein hydrolysate medium now employed in the air-borne mold survey. This medium supports the growth of a large number of the air-borne saprophytic fungi common to this region. 2. 2. There is evidence, however, that this medium is still not the best possible, since readings from the modified Smith-Humfeld salt agar show a mold count almost double the mold count obtained on Mehrlichs salt agar and almost triple the mold count from the casein hydrolysate salt medium. 3. 3. As a result, therefore, experiments with a further modified Smith-Humfeld salt medium, a purified malt salt agar, and reduced strengths of the casein hydrolysate medium are being continued. 4. 4. None of these media will disclose the presence of air-borne spores of obligate parasites or spores of some other fungi as mushrooms and wood-rotting fungi which may often be present in considerable numbers, but they may considerably increase the value of the surveys now being conducted.

Evaluating condition and storability of sunflower seeds

Abstract The average moisture content of samples of sunflower seeds (achenes) taken from bins at Crookston, Minnesota, was 11·8 per cent as determined by a meter at the bin site, but the moisture content of individual samples, as determined by oven drying, ranged from 9·0 to 15·7 per cent. No increase in storage fungi occurred, even in the seeds of high moisture content, so long as the temperature remained below about 5°C but a combination of moisture content above 11·0 per cent and a temperature of 21°C or above, resulted in fairly rapid invasion by Aspergillus glaucus . Periodic sampling, followed by tests of the individual samples for moisture content and field and storage fungi, provided data for accurate evaluation of condition of the seeds throughout the bins.

The mycotoxin potential of peanuts (groundnuts): The U.S.A. Viewpoint☆

Abstract The mycotoxin potential of a plant product can be gauged by seeking answers to two of three questions basic to the mycotoxin problem; namely, ‘Which of the fungi invading the product can be toxicogenic?’, and ‘How can they become established in the product?’ Both questions relate to the quite new science of microbial synecology. In contrast, the third basic question (‘What factors are necessary for toxin production by a given toxicogenic fungus?’) relates to the much older but more complex science of microbial autecology. Fruits of Arachis hypogaea L., called ‘peanuts’ (U.S.A.) or ‘groundnuts’, are completely hypogeic in their development, and there seems to be a successional invasion of them by soil-borne or ‘field’ fungi with the result that sound mature fruits have a dormant or quiescent endogeocarpic microfloral community. Results of co-operative research in six peanut producing states (U.S.A.) and at the University of Minnesota, interpreted in the light of present-day peanut harvesting practices in the U.S.A., justify the following conclusions: (1) Aspergillus flavus can be toxicogenic under field conditions and is a serious problem. (2) Many other of the fungi from the peanut endogeocarpic community are toxicogenic under laboratory conditions. (3) Until the conditions under which such fungi may become toxicogenic are better known, their presence in lifted groundnuts constitutes a real mycotoxin potential. (4) The genera posing the greatest threat are, in estimated order of importance, Penicillium, Aspergillus (primarily because of A. flavus), Alternaria, and Fusarium. (5) Much care must be exercised with peanuts after lifting, to minimise opportunity for proliferation of such fungi. This care must be exercised at least until we determine extent to which such fungi might be expected to produce toxins in peanut fruits on the farm and during subsequent handling.

Some biological and chemical characteristics of damaged corn

Abstract The predominant fungi isolated from damaged kernels of corn (maize) plated on agar media were species of Aspergillus (mainly A. glaucus) and Penicillium. Masses of spores and mycelium of Aspergillus, Penicillium, Cladosporium and Fusarium were present in the cavities of the embryo of many kernels from which no fungi grew. Some samples had a high percentage of blue-eye kernels, evidently caused mainly by A. restrictus and A. glaucus. The embryos of all damaged kernels were decayed to some extent by fungi. Weight averaged 51 · 7 lb/bu, not much below that of sound corn. Fat acidity values ranged from 90–324. No aflatoxin was found in any of the 24 samples tested.

Galerina Hypnorum Fruiting on Cattail and in Pure Culture

A gilled fungus identified according to descriptions by Smith and Singer (2) and by Kauffman (1) as Galerina hypnorum (Schrank ex Fr.) Kiihner fruited on the leaf sheaths of cattails (Typha latifolia L. and T. angustifolia L.) that had been transplanted into water tanks in the greenhouse. Eight fruit bodies developed on five different cattails during a 4-wk period in late June and early July. All of them developed on the shady side of the stem and on a portion of the leaf sheath that appeared to be senescent; typical examples are shown in FIGS. 1, 2. According to Smith and Singer (2), many species of Galerina require a special habitat such as mosses, conifer needles, burned ground, and hardwood logs. Kauffman (1) recorded that G. hypnorum usually occurs on mosses, but, so far as we are aware, this is the first report of its occurrence on Typha. Cultures of the fungus were obtained readily from cast spores placed on sterile agar, and were subsequently transferred to a number of media -potato dextrose, malt, cornmeal, Czapek Dox, and water agar with and without pieces of Typha leaves. Fruit bodies (FIG. 3) developed on the water agar containing portions of Typha leaves, but not on the other media tested, usually only one fruit body per dish or flask. 879

Two Cases of Unusual Development of Fruit Bodies

Those who are familiar with fleshy Agaricales know that the geotropic response which results in an orientation of pores, gills, or other spore bearing surfaces perpendicular to the surface of the earth, sometimes goes awry, especially if fruit bodies are diseased or mechanically injured. Fruit bodies produced in unnatural environments, as on agar cultures or on wood in jars, sometimes exhibit a capricious orientation of pores or gills, indicating that forces other than gravity are involved in such orientation. Following will be described two interesting cases of such nongeotropic development. The first case involves an agaric (Russula sp., tentatively identified as R. atropurpurea Peck) observed at Itasca Park, Minnesota, in September, 1937. More than a decade before that time several pits about 5 feet square and 4 to 5 feet deep had been dug for experimental purposes in the level ground in a Jack pine stand. During a rainy spell in September, 1937, when fleshy fungi were rather abundant, the writer observed 2 fruit bodies of this species of Russula growing out of the vertical walls of one of the pits. One appeared about a foot from the surface of the ground, the second about 2 feet from the surface and on an adjoining wall. The stem of each, although short, extended straight out from the vertical wall, no upward curve being visible. The cap in each case was parellel to the wall. The gills were normal, although the free edges of those on the upper side bent over as they lost their turgidity with age, as can be seen in figure 1. In other words, the fruit bodies were oriented in the same way to the perpendicular surface from which they grew, as fruit bodies growing on approximately