Effects of fungicides on Aspergillus fumigatus

Aspergillus fumigatus was the most frequently isolated thermophilous fungus from green leaf surfaces. The application of fungicides significantly reduced the frequency of its occurrence there. A. fumigatus was relatively tolerant to fungicides. On Captan-, Thiram-, and Verdasan-treated leaves, A. fumigatus constituted 66%–80% of the total number of isolates obtained at 45°C from each treatment while Dicloran did not depress the percentages. At 45°C, A. fumigatus was found to be strongly cellulolytic with a slow rate of radial extension on YpSs agar and rapid rate of mycelial growth in Czapek Dox liquid medium. Increasing concentrations of all four fungicides reduced or prevented growth, sporulation, starch depletion and cellulose clearing of A. fumigatus. The fungus could tolerate higher concentrations of HgCl₂ than of Verdasan. 0.5 g/ml of the four fungicides altered the rates of mycelial growth but not the maximum amount of mycelial dry weight attained.     

Effects of temperature and fungicides on Chrysosporium pannorum (Link) Hughes

C. pannorum was isolated in low frequencies and only in the colder months from untreated soil and leaves and from those treated with Captan, Dicloran and Thiram. The fungus was isolated throughout the year as the major species from Verdasan-treated substrates and it occurred with increased frequencies immediately after application of the fungicide. The abundance of C. pannorum on Verdasan-treated substrates was attributed to the ability of the fungus to utilise the fungicide rather than to the absence of faster growing competitor species. C. pannorum was shown to be a slow growing and moderately cellulolytic fungus with maximum rates of growth, germination and cellulose clearing at between 15° and 20°C. Increasing concentrations of the fungicides retarded or prevented growth and activity of the fungus. C. pannorum could grow, germinate and clear cellulose in higher concentrations of Verdasan than could other species studied. C. pannorum was more tolerant of HgCl₂ than of Verdasan. The fungus could detoxify up to 3 g/ml active ingredient of Verdasan (=120 g/ml of the formulated fungicide) in liquid culture.     

Growth of Trichoderma harzianum and Myceliophthora thermophila in palm oil sludge

Uncentrifuged palm oil mill sludge (POS) diluted to about 50% (v/v in tap water) supports good mycelial growth of Myceliophthora thermophila and Trichoderma harzianum. Both of the selected fungi are non-toxic to mice. After 24 h M. thermophila grown in batch culture in POS yielded 28.6 g/l of mycelial biomass with biological oxygen demand (BOD) and chemical oxidation demand (COD) reductions of 72% and 74% respectively. T. harzianum yielded 24.4 g/l of mycelial biomass with BOD and COD reductions of 67% and 68% respectively. The crude protein of the mycelial biomass of M. thermophila and T. harzianum was twice that of untreated POS. T. harzianum showed amylolytic activity while M. thermophila was cellulolytic and lipolytic.     

Fungi associated with the aerial parts of Malaysian mangrove plants

The leaf surface fungi associated with nine species of mangrove plants includingAvicennia alba, A. officinalis, Bruguiera parviflora, Ceriops tagal, Rhizophora apiculata, R. mucronata, Sesuvium portulacastrum, Sonneratia alba, andXylocarpus mollucensis were studied using direct observation techniques and leaf washings. Over 40 fungal taxa were isolated from the leaf washings. Of these, species ofAspergillus, Choanephora, Cladosporium, Curvularia, Fusarium, Nigrospora, Penicillium, Pestalotiopsis, Trichoderma, andZygosporium were frequently encountered in the washings of all nine mangrove plants. Fewer species of fungi includingCladosporium oxysporum, Corynespora cassiicola, Fusarium, Penicillium, Pestalotiopsis, andZygosporium were capable of growth on the washed leaves. The major phylloplane fungus on plants with higher leaf tannin content (e.g.B. parviflora, C. tagal, Rhizophora spp., andX. mollucensis) wasPestalotiopsis. Leaves with relatively lower amounts of tannin supported the proliferation ofFusarium as the major fungus. Fungi were present on the plumule and cotyledonous sheath even before the leaves opened.Pestalotiopsis persisted throughout the development and growth of the leaves. Many of the fungi encountered on senescent leaves have been reported in earlier studies to be the primary colonisers of submerged decaying leaves.     

The effects of fungicides on the growth rates of thermophilous fungi

The effects of the fungicides Captan, Dicloran, Thiram, Verdasan and mercuric chloride (HgCl₂) on the radial and mycelial growth rates of thermophilous fungi isolated from living green leaves were studied. On controlplates Thermoascus aurantiacus andTorula thermophila had the highest radial growth rates whileMalbranchea pulchella var.sulfurea andTalaromyces duponti had the lowest growth rates. Good sporulation was seen on all control plates.With increasing concentrations of fungicides the growth rates were correspondingly retarded and sporulation was reduced. At het higher fungicide concentrations the hyphal tips and young hyphae were thicker and warty or granulated.Of the fungi studies,Aspergillus andMucor pusillus were the most tolerant species; they were capable of growth in more concentrations of fungicides compared with the other species.Talaromyces duponti andThermomyces lanuginosus emerged as the most sensitive species.Most marked reductions in the growth rates were produced by Thiram and Verdasan than by the other fungicides. All the ten thermophilous species studied were capable of growth with more concentrations of HgCl₂ than with the organo mercurial Verdasan.Six of the ten thermophilous species studied showed higher radial growth rates compared with the two fastest growing mesophilic species studied;Trlchoderma viride andZygorhynchus moelleri. While M. pusillus was capable of growth in dry weight at 0.05 ppm of all fine fungicides,Sporotrichum thermophile did not show mycelial growth with Verdasan at 0.05 ppm.Thermomyces lanuginosus showed reduced growth rates with Thiram and no mycelial growth with both HgCl₂ and Verdasan.     

Frequency of occurrence of fungi on wood in Malaysian mangroves

Over one hundred fungi have been reported on mangrove wood (Hyde and Jones, 1988; Jones and Kuthubutheen, 1989; Hyde and Jones, unpublished) from tropical and subtropical locations. A variety of factors affect the frequency of occurrence of these fungi, e.g . salinity, length of exposure of substrate, wood species and location within the mangrove. Two aspects are addressed in this paper: a) Comparison of the fungi present at three mangroves in Malaysia (Morib, Kuala Selangor, Port Dickson); and b) The fungi colonising specific mangrove wood, e.g. Avecennia marina, Bruguiera gymnorrhiza. Species diversity was greatest at Port Dickson with 63 fungi recorded while species composition varied from site to site. Common fungi at Morib and Kuala Selangor were Halocyphina villosa and Leptosphaeria australiensis along with Kallichroma tethys and Lulworthia grandispora at the latter site. None of these were common at Port Dickson, the dominant species at this site were Hypoxylon oceanicum and Massarina ramunculicola. A comparison of the fungi occurring on Avicennia marina and Bruguiera gymnorrhiza indicated that Halocyphina villosa was common on both timbers. Species diversity and abundance were greatest on Avicennia with the following fungi listed as common: Eutypa sp., Kallichroma tethys, Marinosphaera mangrovei, Phoma sp. and Julelia avicenniae.     

Fungi associated with the aerial parts of Malaysian mangrove plants

The leaf surface fungi associated with nine species of mangrove plants includingAvicennia alba, A. officinalis, Bruguiera parviflora, Ceriops tagal, Rhizophora apiculata, R. mucronata, Sesuvium portulacastrum, Sonneratia alba, andXylocarpus mollucensis were studied using direct observation techniques and leaf washings. Over 40 fungal taxa were isolated from the leaf washings. Of these, species ofAspergillus, Choanephora, Cladosporium, Curvularia, Fusarium, Nigrospora, Penicillium, Pestalotiopsis, Trichoderma, andZygosporium were frequently encountered in the washings of all nine mangrove plants. Fewer species of fungi includingCladosporium oxysporum, Corynespora cassiicola, Fusarium, Penicillium, Pestalotiopsis, andZygosporium were capable of growth on the washed leaves. The major phylloplane fungus on plants with higher leaf tannin content (e.g.B. parviflora, C. tagal, Rhizophora spp., andX. mollucensis) wasPestalotiopsis. Leaves with relatively lower amounts of tannin supported the proliferation ofFusarium as the major fungus. Fungi were present on the plumule and cotyledonous sheath even before the leaves opened.Pestalotiopsis persisted throughout the development and growth of the leaves. Many of the fungi encountered on senescent leaves have been reported in earlier studies to be the primary colonisers of submerged decaying leaves.