Fungal Colony Growth Research Articles

First Report of Ascochyta rabiei Causing Ascochyta Blight of Cicer pinnatifidum.

In July 2005, small (2 to 5 mm), elongated, dark brown spots on the stems of Cicer pinnatifidum Jaub. & Spach. were observed on plants grown in the rocky hills of the Kahramanmaras Province. To understand this phenomenon, field trips to Kahramanmaras, Adiyaman, and Sanliurfa provinces were conducted in the summer of 2006. C. pinnatifidum plants exhibiting symptoms similar to Ascochyta rabiei (Pass.) Lab. were collected during May and June. The plants had flowers and pods with seeds at the time of collection. Ascochyta blight symptoms on stems were not extensive. None of the plants had leaf symptoms, but one plant had lesions on its pods. Twelve plants exhibiting Ascochyta blight symptoms were taken to the laboratory, and necrotic parts were used for isolation of the fungi on potato dextrose agar (PDA). After 3 to 5 days of culturing on PDA, characteristic beige-to-dark brown colony development of A. rabiei from explants was observed and five isolates from different locations were recovered. The fungal colony growth was slow and limited conidia formed on PDA. The isolates were also cultured on chickpea meal agar (CMA) and Czapek Dox Agar (CDA) media. Abundant conidia formation occurred only on CMA, 10 to 12 days after culturing. Conidia were one-celled similar to that of A. rabiei of chickpea and single-spore isolations were done. C. pinnatifidum and chickpea cv. Gokce (C. arietinum L.) were inoculated with spore suspensions of 5 × 105 spores per ml (2). Ten- to twelve-day-old seedlings were used for inoculation in the experiments. Brown-black lesions at the crown region on C. pinnatifidum seedlings were observed 9 to 10 days after inoculation, and characteristic Ascochyta blight symptoms on stems developed on chickpea cv. Gokce. The fungus was reisolated from the infected seedlings. For molecular characterization, mating type of the isolates was determined by PCR using A. rabiei specific Tail1, Com1, and Sp21 primers (1). A single band of Mat 1.2 specific 500- bp product was amplified by PCR from five of the A. rabiei isolates of C. pinnatifidum. This confirmed that the isolates from C. pinnatifidum are A. rabiei.

Fungistatic Activity of Freshly Killed Termite,Nasutitermes acajutlae, Soldiers in the Caribbean

Termites may have high exposure to both pathogenic and competitive fungal species. Previous studies have shown anti-fungal properties of the primary components (α-pinene and limonene) of Nasutitermes frontal glands that are present on soldiers. In this study, the termite Nasutitermes acajutlae (Isoptera: Termitidae) was used to examine if the growth of naturally occurring fungi was inhibited by soldiers, as compared to workers that do not have frontal glands. Soldiers and workers were killed, surface sterilized, and placed on nutrient agar either singly or in combinations with other termites. Time until appearance of fungus and growth of visible fungal colonies was determined. Fungus appeared significantly earlier in cultures with single workers than with single soldiers (P < 0.001). Once fungus appeared, there were no significant differences in growth rate. When worker and/or soldier fluids were combined in one culture, fungal growth appeared later in cultures containing soldiers; growth was significantly slower in colonies with 5 workers and 5 soldiers than in cultures with 5 workers alone; P < 0.001. Finally, growth appeared later in cultures with 5 soldiers than in cultures with one soldier, suggesting a dose-response. Fungi that grew from termites were mostly non-pathogenic, suggesting the anti-fungal properties of soldiers may inhibit both pathogens and competitors.

Bactericidal and antifungal activities of a low molecular weight chitosan and its N-/2(3)-(dodec-2-enyl)succinoyl/-derivatives

Low molecular weight chitosan (4.6 kDa) and N-/2(3)-(dodec-2-enyl)succinoyl/-derivatives of different degrees of substitution were tested for their antimicrobial activity against Escherichia coli, Pseudomonas aureofaciens, Enterobacter agglomerans, Bacillus subtilis, Candida kruisei and Fusarium oxysporum f. sp. radicis lycopersici. The results indicated that the chitosans show high activities against all bacteria, yeast and filamentous fungus. In fact, they suppressed fungal colony growth and inhibited fungal spore germination at 0.01% (w/v) concentration. A higher activity of chitosan and its derivatives was obtained with a substitution degree of 3 mol% for E. coli and B. subtilis, while a substitution degree of 9 mol% was usually preferable for increased activity against P. aureofaciens, E. agglomerans and C. kruesei.

Statistical analysis of structural and kinetic characteristics of fungal colony growth with Trichoderma viride Pers.: S.F. Gray

The mycelial colonies of Trichoderma viride were grown between two thin cellophane films for exact measurements. The results obtained testify to the fact that in a mature colony the average length of intercalary cells, the average number of intercalary cells in an internode and the average internode length are stable. At this stage of morphogenesis the mean internode length is shown to be equal to the product of the average intercalary cell length and the average number of intercalary cells in an internode. The coefficients of variation of the internode length and the number of intercalary cells in an internode are found to be equal. The length of an intercalary cell and duration of the doubling cycle of an apical cell of T. viride obey the law of Gamma distribution. According to our observations, the Gamma distribution is typical for the length and duration of the doubling cycle of any bacterial cells and cells of any multicellular organisms.

Effects of selected pesticides and adjuvants on germination and vegetative growth of Phomopsis amaranthicola, a biocontrol agent for Amaranthus spp.

Summary Phomopsis amaranthicola, a bioherbicide agent for Amaranthus spp., was tested in vitro for its compatibility with commercial formulations of 16 adjuvants, 24 herbicides, nine fungicides and four insecticides at 2X, 1X (highest labelled product dose rate), 0.75X, 0.5X and 0.25X concentrations. These chemicals were tested for their effects on spore germination. Selected herbicides and fungicides at 1X were also tested for their influence on colony growth and sporulation. All tested compounds were finally categorized in compatibility classes regarding germination, mycelial growth and sporulation such as low, medium and high compatibility. High compatibility in terms of germination and fungal colony growth was only observed with the herbicide bentazone. Many of the adjuvants tested were highly compatible in the germination studies. Most fungicides and insecticides had medium and low compatibility with P. amaranthicola. Effects of pesticides on spore germination did not fully correspond with their effects on colony growth. Thus, it is possible to integrate the use of P. amaranthicola with some herbicides, fungicides, insecticides and adjuvants but not others. A case‐by‐case selection of application methods, such as tank‐mix or sequential application, along with proper timing of applications of the fungus and the chemical agents will be necessary.

Leucinostatin-A loaded nanospheres: characterization and in vivo toxicity and efficacy evaluation

Leucinostatin A (Leu-A) is a nonapeptide exerting a remarkable activity especially against Candida albicans and Cryptococcus neoformans; nevertheless, its employment is limited due its toxicity. Therefore, we recently developed liposomal formulations, as suitable delivery systems, in order to increase its therapeutic index. However, liposomes present disadvantages related to their long-term instability. For this reason poly(lactic-co-glycolic) nanospheres (NS) were chosen as alternative colloidal carriers for Leu-A delivery. NS were formulated by spontaneous emulsification solvent diffusion method. This study investigates the effects of different parameters on drug encapsulation efficiency and particle size as well. The best preparation obtained was also characterized for its in vitro release, in vivo acute toxicity (LD 50), and effectiveness against C. albicans in mice. In vitro release was performed over 100 h and resulted sufficiently sustained with more than 93% of the peptide released. Acute toxicity showed that the LD 50 was increased more than 18-fold and the study on systemic candidiasis models revealed high effectiveness of the NS in reducing either the growth of fungal colonies in infected mice liver or in the mortality index. In conclusion, we can propose that Leu-A loaded NS could represent a new promising therapeutic system against Candida infection.

A dynamic simulation model for powdery mildew epidemics on winter wheat*

A system dynamic model for epidemics of Blumeria graminis (powdery mildew) on wheat was elaborated, based on the interaction between stages of the disease cycle, weather conditions and host characteristics. The model simulates the progress of disease severity, expressed as a percentage of powdered leaf area, on individual leaves, with a time step of one day, as a result of two processes: the growth of fungal colonies already present on the leaves and the appearance of new colonies. By means of mathematical equations, air temperature, vapour pressure deficit, rainfall and wind are used to calculate incubation, latency and sporulation periods, the growth of pathogen colonies, infection and spore survival. Effects of host susceptibility to infection, and of leaf position within the plant canopy, are also included. Model validation was carried out by comparing model outputs with the dynamics of epidemics observed on winter wheat grown at several locations in northern Italy (1991–98). Simulations were performed using meteorological data measured in standard meteorological stations. As there was good agreement between model outputs and actual disease severity, the model can be considered a satisfactory simulator of the effect of environmental conditions on the progress of powdery mildew epidemics.

Nutritional influence on fungal colony growth and biomass distribution in response to toxic metals.

This work examines nutritional influence on fungal colony growth and biomass distribution in response to toxic metals. In low-substrate solid medium, 0.1 mM Cd, Cu and Zn caused a decrease in radial expansion of both Trichoderma viride and Rhizopus arrhizus. However, as the amount of available carbon source (glucose) increased, the apparent toxicity of the metals decreased. These metals also affected the overall length of the fungal mycelium and branching patterns. In low-nutrient conditions, T. viride showed a decrease in overall mycelial length and number of branches in response to Cu, resulting in an extremely sparsely branched colony. Conversely, although Cd also reduced overall mycelial length to about one-third of the control length, the number of branches decreased only slightly which resulted in a highly branched colony with many aberrant features. Cu and Cd induced similar morphological changes in R. arrhizus. A large-scale mycelial-mapping technique showed that disruption of normal growth by Cu and Cd resulted in altered biomass distribution within the colony. When grown on metal-free low-substrate medium, T. viride showed an even distribution of biomass within the colony with some allocation to the periphery. However, Cu caused most of the biomass to be allocated to the colony periphery, while in the presence of Cd, most biomass was located at the interior of the colony. These results imply that such alterations of growth and resource allocation by Cu and Cd may influence success in locating nutrients as well as survival, and that these metals have individual and specific effects on the growing fungus.

Nutritional influence on fungal colony growth and biomass distribution in response to toxic metals

This work examines nutritional influence on fungal colony growth and biomass distribution in response to toxic metals. In low-substrate solid medium, 0.1 mM Cd, Cu and Zn caused a decrease in radial expansion of both Trichoderma viride and Rhizopus arrhizus. However, as the amount of available carbon source (glucose) increased, the apparent toxicity of the metals decreased. These metals also affected the overall length of the fungal mycelium and branching patterns. In low-nutrient conditions, T. viride showed a decrease in overall mycelial length and number of branches in response to Cu, resulting in an extremely sparsely branched colony. Conversely, although Cd also reduced overall mycelial length to about one-third of the control length, the number of branches decreased only slightly which resulted in a highly branched colony with many aberrant features. Cu and Cd induced similar morphological changes in R. arrhizus. A large-scale mycelial-mapping technique showed that disruption of normal growth by Cu and Cd resulted in altered biomass distribution within the colony. When grown on metal-free low-substrate medium, T. viride showed an even distribution of biomass within the colony with some allocation to the periphery. However, Cu caused most of the biomass to be allocated to the colony periphery, while in the presence of Cd, most biomass was located at the interior of the colony. These results imply that such alterations of growth and resource allocation by Cu and Cd may influence success in locating nutrients as well as survival, and that these metals have individual and specific effects on the growing fungus.

Stachybotrys-Toxine in einer Münchner Wohnung mit Wasserschaden

This paper presents a case report of indoor Stachybotrys toxins in Germany. In the summer of 2000, heavy rainfall and a leakage of the gutter system of an appartement house in Munich, Germany, caused a severe water damage in one of the appartments. The appartment was at that time occupied by two of the authors (ES, EU). A wall (covered with wallpaper) in one room in particular was most strongly affected, about 6–8 m2 of the wallpaper became very wet. Large parts of this wet wallpaper were within days infested by multiple circumscribed round, grey-black colonies (0.5–5 cm in diameter) of presumtiveStachybotrys spp.. At the same time, the air in this room became very damp and oppressive. Several persons reported burning sensations on the mucous membranes of the eye, nose, and larynx, followed by headache symptoms, as soon as a few minutes after they had entered this room. Inadvertent skin contact with one of the fungal colonies by one person resulted in burning sensations immediately, but symptoms disappeared after thorough rinsing of the skin with water. The infested room was evacuated, and samples were taken from the wet wallpaper at areas (1) in the center of the most heavy fungal colony growth, (2) several cm away from colony growth, and (3) from locations which were wet but about 1 m away from visible colony growth. The samples were extracted with methanol, the extract diluted with buffer solution and analysed by competitive enzyme immunoassay (EIA) for roridin A. Due to cross-reactivity, this EIA detects several macrocyclic trichothecenes produced byStachybotrys spp.. Heavily infected pieces of wallpaper were strongly contaminated with toxins, with maximum concentrations of 1.1 microgram per cm2 (Roridin A equivalents). Wet but visibly not infected samples of wallpaper were negative in the EIA. Considering a EIA cross-reactivity of satratoxin H (the major Stachybotrys-toxin) of 15%, the actual maximum toxin concentration would correspond to 6 microgram of satratoxin H per cm2. As far as we know, this is the first documented case of indoor Stachybotrys toxins in Germany. The toxin concentration by far exceeds the minimum toxin level required for skin toxicity, and was considered as unhealthy. Health authorities in Munich were informed but were unable to provide assistance, probably because awareness of the importance and the possible health risks caused by indoor mycotoxins is not yet widespread in Germany. Reporting and monitoring programs for mycotoxins in water-damaged buildings seem to be necessary to provide insight into the occurrence of similar cases as the one described here.

Using chimeric hypoviruses to fine-tune the interaction between a pathogenic fungus and its plant host.

Infectious cDNA clones of mild (CHV1-Euro7) and severe (CHV1-EP713) hypovirus strains responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus Cryphonectria parasitica were used to construct viable chimeric viruses. Differences in virus-mediated alterations of fungal colony morphology, growth rate, and canker morphology were mapped to a region of open reading frame B extending from nucleotides 2,363 to 9, 904. By swapping domains within this region, it was possible to generate chimeric hypovirus-infected C. parasitica isolates that exhibited a spectrum of defined colony and canker morphologies. Several severe strain traits were observed to be dominant. It was also possible to uncouple the severe strain traits of small canker size and suppression of asexual sporulation. For example, fungal isolates infected with a chimera containing nucleotides 2363 through 5310 from CHV1-Euro7 in a CHV1-713 background formed small cankers that were similar in size to that caused by CHV1-EP713-infected isolates but with the capacity for producing asexual spores at levels approaching that observed for fungal isolates infected with the mild strain. These results demonstrate that hypoviruses can be engineered to fine-tune the interaction between a pathogenic fungus and its plant host. The identification of specific hypovirus domains that differentially contribute to canker morphology and sporulation levels also provides considerable utility for continuing efforts to enhance biological control potential by balancing hypovirulence and ecological fitness.

EFEITO ANTAGÔNICO DE Trichoderma sp. NO DESENVOLVIMENTO DE Beauveria bassiana (Bals.) Vuill. e Metarhizium anisopliae (Metsch.) Sorok

Este trabalho teve por objetivo avaliar o efeito de Trichoderma sp. no desenvolvimento de Beauveria bassiana e Metarhizium anisopliae. Trichoderma sp., B. bassiana (isolado 634) e M. anisopliae (isolado E-9) foram inoculados em meio BDA, com intervalos de 0, 48, 120 e 168 horas entre a inoculação de Trichoderma sp. e dos entomopatógenos. Avaliou-se o crescimento radial das colônias nos períodos de 48 e 120 horas após a inoculação de Trichoderma sp., sendo que este afetou o desenvolvimento dos entomopatógenos quando inoculado simultaneamente ou após 48 horas. B. bassiana e M. anisopliae desenvolveram-se normalmente quando inoculados 168 horas antes de Trichoderma sp.. Também foi avaliado o efeito de um extrato de Trichoderma sp. sobre os entomopatógenos, com a adição de 0,1; 0,5; 1,0 e 5,0 ml de extrato/100,0 ml de meio, onde foram inoculados os entomopatógenos. Foram medidos os diâmetros de colônias e o número de conídios produzidos por B. bassiana e M. anisopliae na presença do extrato. A concentração de 5,0 ml de extrato/100,0 ml de meio alterou o crescimento e a conidiogênese de B. bassiana. O fungo M. anisopliae foi afetado a partir da adição de 1,0 ml de extrato/100,0 ml de meio.

Use of Bicarbonates to Inhibit in vitro Colony Growth of Botrytis cinerea.

Fungicide resistance in Botrytis cinerea has caused increased concerns about losses due to gray mold on many important agricultural and horticultural crops. Since bicarbonates have been reported to be an effective control of powdery mildew on greenhouse roses, the purpose of this research was to determine the effectiveness of bicarbonates against B. cinerea. Assessments were made of in vitro fungal colony growth in response to ammonium, potassium, and sodium bicarbonates. Bicarbonates inhibited colony growth at concentrations as low as 20 mM. In addition, comparisons of several ammonium, potassium, and sodium salts were conducted to determine whether cation or anion is the active moiety. Although the bicarbonate anion primarily affected growth, the ammonium cation also contributed greatly to fungal growth inhibition. With the exception of dibasic phosphate, only salts with high pKa values or that are reducing agents, or both, decreased colony growth. The effect of pH on B. cinerea was then examined. Since bicarbonate anion concentration is related to pH, this parameter was examined in combination with several salts to separate pH effects from bicarbonate effects. As pH increased from 7.0 to 8.5, colony growth decreased with bicarbonates and phosphates, but not with ammonium sulfate. Since bicarbonates and phosphates decreased colony growth more than could be accounted for from pH alone, and since both have buffering characteristics, buffering capacity was examined and found to decrease colony growth but not as much as bicarbonate. Therefore, bicarbonates control B. cinerea colony growth in vitro, and both pH and buffering capacity contribute to, but are not solely responsible for, growth inhibition.

A mathematical model applied to the fungal colony growth of Sclerotium rolfsii

Colonies of Sclerotium rolfsii growing on solid medium showed a linear increase in radius simultaneously with exponential changes in colonial weight. The mathematical model developed by Koch (Koch, A.L. 1975. J. Gen. Microbiol. 89, 209Ð216) to describe similar kinetics of mycelial growth was applied. Most of the parameters deÞned in the mentioned model were directly measured or calculated, except the values of K (maximum mycelium carrying capacity) and S (initial mycelial density) which were Þtted to the experimental data of growth at 30iC and 23iC. The ratios K/S at 30iC and at 23iC were 18.8 and 1200 respectively, being consistent with two-dimensional growth. The model was predictive only during the exponential increase of the colony weight.

Fungicidal activity of Ranunculus asiaticus and other weeds against Fusarium oxysporum f.sp. lycopersici

SummaryThe effects of aqueous extracts of some common weed species against Fusarium oxysporum Schlecht f.sp. lycopersici (the causal agent of tomato wilt disease) were investigated under laboratory conditions. Anagallis foemina L., Cerastium dicotomum L., Falcaria vulgaris L., Ranunculus asiaticus L., Scorpiurus mur‐icatus L. and Solanum nigrum L. extracts were the most toxic to the fungus. Further studies on buttercup (Ranunculus asiaticus L.) showed that fresh shoot extract of this species prevented growth of F. oxysporum when incorporated into agar medium. Extracts of different parts of the plant inhibited fungus growth and sporulation, but the fungitoxicity decreased with incubation period with only slight changes in the toxicity of fresh shoot extract. The shoot and fresh parts extracts were more toxic than root and dried tissue extracts. Addition of 0.5 ml fresh shoot or 1 ml fresh root extract to the growing medium significantly reduced fungal colony growth, and the effect was extract concentration dependent. Fresh shoot extract of R. asiaticus added to a liquid medium significantly reduced mycelial dry weight compared with the control, and incorporation of 0.1 g dried shoot or 0.2 g dried roots in the media strongly inhibited fungus growth. Results of a pot experiment showed no harmful effects of R. asiaticus extracts on tomato growth.

Suppression of Botrytis blight in cut rose flowers with gibberellic acid. Effects of exogenous application of abscisic acid and paclobutrazol

The postharvest development of Botrytis blight in rose flowers ( Rosa × hybrida cv. Mercedes) was suppressed when flower buds were sprayed with 1 mM solution of gibberellic acid (GA 3 ). The development of the disease was promoted by application of abscisic acid (ABA) and the suppressive effect of GA 3 was reduced when GA 3 solution was supplemented with ABA. The GA 3 -imposed suppression of Botrytis blight was enhanced by addition of paclobutrazol (PBZ) to the GA 3 solution, but the development of the disease was not affected by PBZ alone. Germination of conidia and germ-tube elongation of Botrytis cinerea in vitro were unaffected by ABA and PBZ, whereas linear growth of fungal colonies was promoted by ABA but was inhibited by PBZ.

Green Leaf Volatiles Inhibit Conidial Germination of the Entomopathogen Pandora neoaphidis (Entomopthorales: Entomophthoraceae)

We tested whether a tobacco, Nicotiana tabacum (L.), plant defense against tobacco aphids, Myzus nictianae (Blackman), might also inhibit the entomopathogenic fungus Pandora neoaphidis (Remaudiere & Hennebert). Growth of fungal colonies exposed to macerated and unmacerated tobacco leaves, hexanal, (E)-2-hexenal, and (E)-2-hexenol was strongly suppressed compared with controls. Large numbers of ungerminated conidia were recovered from the media surrounding the treated colonies, whereas few ungerminated conidia were found in media surrounding the controls. Conidia were then collected onto glass coverslips and exposed to the same treatments during the first 4 h after conidial relase. Relative to controls, hexanal substantially suppressed conidial germination, the leaf material suppressed germination substantially more than hexanal and (E)-2-hexenal was the strongest inhibitor indicating that the principal effect of the plant volatiles was inhibition of conidial germination. Based on scanning electron microscope examination, when conidia were deposited directly onto live aphids instead of cover slips, these volatiles had no effect on aphid infection rates, indicating that the inhibition of conidial germination does not occur when conidia are actually on an aphid surface. Finally, germination of conidia exposed to volatiles of plants previously infested with aphids was substantially suppressed relative to uninfested controls. These studies suggest that tobacco plant volatiles produced in response to wounding such as aphid feeding inhibit conidial germination by the entomopathogen unless the conidia are in direct contact with the aphid integument. We suggest that the conidia respond to presence of wound-induced volatiles by delaying germination so as to increase their probability of finding an aphid host ; the conidia use the plant's wound response as a cue to indicate host proximity. A conceptual model of this process is presented.

Uptake of Glucose and Phosphorus by Growing Colonies of Fusarium oxysporum as Quantified by Image Analysis

Olsson, S. 1994. Uptake of glucose and phosphorus by growing colonies of Fusarium oxysporum as quantified by image analysis. Experimental Mycology 18, 33-47. The simplest of all heterogeneous environments for fungal colony growth is the petri dish with an agar medium. As the colony grows there will be a depression of nutrient concentrations under the colony caused by the uptake of nutrients by the growing colony. Image analysis methods have been developed for measuring medium concentrations of glucose and phosphorus with simultaneous biomass density determinations in agar systems. Maps of the concentrations in the agar medium under the colony and of colony biomass density were produced. A new method for weighing fungal colonies grown on agar is also presented. For Fusarium oxysporum phosphorus and glucose uptake from the medium was the same irrespective of the C/mineral ratios in the medium within the measured range of ratios. Even the concentration profiles of the nutrients under the colony were the same irrespective of nutrient ratios. Distribution of biomass density was affected by differences in glucose concentrations, being highest at the colony margin at the lower concentrations. The results indicate that the fungal colony is able to take up nutrients at the margin in excess of the local needs.

A quantitative assessment of the antimicrobial activity of garlic (Allium sativum)

An aqueous extract of freeze-dried garlic (Allium sativum), when incorporated into growth media, inhibited many representative bacteria, yeasts, fungi and a virus. All microorganisms tested were susceptible to garlic. Quantitative assessment of the minimum inhibitory concentrations for bacteria and yeasts showed values ranging from 0.8 to 40.0 mg garlic ml(-1). Fungal radial colony growth was inhibited by at least 25% at concentrations as low as 2.0 mg garlic ml(-1). The 50% endpoint neutralization titre for rotavirus was 2.4 to 2.8 μg ml(-1). Lactic acid bacteria were the least sensitive microorganisms to the inhibitory effects of garlic. In mixed culture studies of Lactobacillus acidophilus and Escherichia coli, garlic prevented the establishment of E. coli, although the final outcome of competition was not affected.

The response of three soil fungi to dalapon and diuron treatments

AbstractDalapon and diuron are two common herbicides used for the control of weeds. A study of the response of Gliocladium virens, Trichoderma hamatum and T. koningii in cultures to the herbicides was carried out. Changes in fungal colony morphology and growth and sporulation rates in the presence of up to 105 mg herbicide litre−1 were monitored. The three fungi were not adversely affected at a concentration of 103 mg litre−1. Changes in colony morphology and decreases in growth and sporulation rates were evident at the maximum test concentration (105 mg litre−1) of both herbicides. These generally recovered when the fungi were replated in the absence of the herbicides.