Effect of soil treatment with the organophosphorus insecticide Profenfos on the fungal flora and some microbial activities.

Tests were conducted to determine the effects of Profenfos [(0-(4-bromo-2-chlorophenyl) 0-ethyl S-n-propyl-phosphorothioat] on fungal populations and some activities in soil. Profenfos (at 5.4 micrograms active ingredient/g dry soil), has a significant adverse effect on the count of total fungi after 2, 4 and 6 weeks after treatment. This effect was completely alleviated after longer incubation. Incorporation of this insecticide into the agar medium inhibited the total count of soil fungi at 6.4 and 38.4 micrograms ml-1. Initial activation followed by a decrease in CO2 output occurred in soil treated with 5.4 micrograms a.i./g. The two doses of Profenfos accelerated urease activity for 6 weeks after soil treatment, but inhibited the enzyme activity after longer periods. An inhibitory effect on nitrate reductase activity was observed with some insecticide treatments in the early stages of incubation followed by an activation in certain cases.

Effect of glyphosate on fungal population, respiration and the decay of some organic matters in Egyptian soil.

Glyphosate (Roundup), when applied to the soil usually did not exert any significant effect on the total count of soil fungi after all periods of the experiment except after 6 and 10 weeks where the count was inhibited by the two doses used (1.84, 9.2 mg active ingredient/kg dry soil). When the herbicide was incorporated into the agar medium the count of total fungi, Acremonium strictum and Aspergillus fumigatus was significantly increased by the two doses used and of Penicillium glabrum by the high dose only. However, P. funiculosum was completely eliminated by the high dose. Oxygen consumption in soil treated with glyphosate was significantly inhibited by the high dose after 2 weeks and by the two doses after 6, 8 and 10 weeks. Glyphosate exerted two significant effects of stimulation and inhibition on the rate of the decay of stem segments of three plants at certain treatments of dose and time.

Phyllosphere and phylloplane fungi of qat in Sana'a, Yemen Arab Republic.

Eighty six species belonging to thirty one genera were collected from the qat phyllosphere (30 genera and 78 species) and phylloplane (20 genera and 64 species) of 24 varieties tested. In the phyllosphere the most frequent genera were Cladosporium, Aspergillus and Alternaria followed by Penicillium, Drechslera, Fusarium, Curvularia, Phoma and Chaetomium. From the preceding genera the most prevalent species were C. herbarum, C. macrocarpum, A. niger, A. flavus, A. alternata, A. phragmospora, P. citrinum, P. notatum, D. spicifera, D. halodes, D. hawaiiensis, F. oxysporum, F. moniliforme, C. lunata, P. humicola, P. herbarum and C. globosum. In the phylloplane the order of genera frequency was more or less the same, while the most common species were C. herbarum, C. sphaerospermum, A. niger, A. flavus, A. alternata and A. tenuissima.

Selective effects of two systemic fungicides on soil fungi.

BAS 317 00F was not toxic to the total count of fungi after 2 days but was regularly significantly toxic at the three doses after 5, 20 and 40 days and toxic at the low and the high doses after 80 days. In the agar medium, it was toxic to the counts of total fungi. Aspergillus, A. terreus, Rhizopus oryzae and Mucor racemosus at the high dose. Only the mycelial growth of Trichoderma viride which was significantly inhibited by the three doses when this fungicide was added to the liquid medium. Polyram-Combi induced two effects on the total population of soil fungi. One inhibitory and this was demonstrated almost regularly after 2, 10 and 40 days and the other stimulatory after 80 days of treatment with the low and the high doses. In the agar medium, this fungicide was very toxic to total fungi and to almost all fungal genera and species at the three doses. Several fungi could survive the high dose. In liquid medium, the test fungi showed variable degree of sensitivity and the most sensitive was Gliocladium roseum which was completely eradicated by the three doses.

Rhizosphere fungi of five plants in Egypt.

75 species which belong to 25 genera were collected during this investigation. All of these fungi were previously isolated from Egyptian soils and other sources. The total count and the number of genera and species in the rhizosphere soil of the 5 plants were regularly higher than in non-rhizosphere soil. The composition of the rhizosphere fungus flora was considerably influenced by the type and the age of the plant. The most prevalent fungi in the rhizosphere of the test plants after 45, 90, and 150 days were as follows: in Helianthus annuus, Stachybotrys atra and Aspergillus niger; in Chrysanthemum coronarium, Cladosporium herbarum, A. sydowii and Penicillium funiculosum; in Nigella sativa, Fusarium moniliforme and A. sydowii; in Datura innoxia, A. fumigatus and A. terreus; in Hyoscyamus muticus, C. herbarum and A. sydowii; and in soil, P. funiculosum, A. terreus and A. niger. The counts of total fungi and most of the common fungal species, except in the case of Datura innoxia, reached their maxima after 90 days and sharply declined after 150 days.

Effect of five pesticides on the mycelial growth of some soil and pathogenic fungi.

The effect of three doses (the lowest is the recommended dose in the field) of 5 pesticides namely: Ceresan, Orthocid (fungicides), VCS-438 (herbicide), and Dursban and Dipterex (insecticides) on the mycelial dry weight of Aspergillus fumigatus. Fusarium moniforme, Pencillium italicum, and Sclerotium ceprivorum was tested 2, 4, 6, 8 and 10 days after treatment. All the pesticides induced inhibition of mycelial growth of the test fungi. Only VCS-438 at the low dose was stimulatory to F. moniliforme after 4 and 6 days and to P. italicum after 4 days. The rate of inhibition was influenced by the type of fungus, the age of the mycelium, and the dose of the pesticide. At the end of the experiment the two fungicides were detoxified by the test fungi with a rate higher than that of the other pesticides.

Toxigenic fungi isolated from Roquefort cheese.

To evaluate the potential for mycotoxin production by fungi contaminating blue-veined cheese, as well as by the ripening fungus, Penicillium roqueforti, the fungal flora of six of local and imported brands was determined. A total of 19 fungi were isolated from the six brands tested. Fourteen of the isolates were toxic to chicken embryos. The toxigenic fungi produced the following mycotoxins: Aspergillus fumigatus, kojic acid; A. versicolor, sterigmatocystin; Penicillium roqueforti, penicillic acid and unidentified toxic metabolites.