First report of anthracnose on Spigelia anthelmia caused by Colletotrichum karstii and Colletotrichum siamense in Brazil

Journal of Plant Diseases and Protection - In Brazil, Spigelia anthelmia is an herbaceous weedy plant normally used for the treatment of helminths in humans and animals. Leaves and stems of S....     

Identification of Colletotrichum siamense causing litchi pepper spot disease in mainland China

Litchi (Litchi chinensis) pepper spot disease results in black spotting symptoms on litchi fruits. This disease was first observed on litchi cultivar Guiwei, in Guangzhou, China, in 2009, and then found widespread in other litchi-growing regions of China. Colletotrichum isolates were consistently recovered from typical black spot lesions of diseased fruits with frequency ranging from 83% to 100%. Three representative Colletotrichum isolates from Maoming, Guangzhou and Shenzhen were selected for identification and pathogenicity testing in the field. Based on morphology and phylogenetic analysis using the ribosomal internal transcribed spacer region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), calmodulin (CAL), actin (ACT), β-tubulin (TUB2) and glutamine synthetase (GS) gene sequences, the three isolates were identified as C. siamense. In the pathogenicity experiments, typical symptoms appeared on the inoculated litchi fruits, including black spots and green patches around these black spots. These symptoms were consistent with the symptoms originally observed in the field. Colletotrichum siamense was successfully reisolated from the typical black spot lesions of the inoculated litchi fruits. To the authors' knowledge, this is the first report on characterization of C. siamense as the causal agent of litchi pepper spot disease in mainland China by successful inoculation on fruits under field conditions.     

Phylogenetic and morphological identification of Colletotrichum boninense: a novel causal agent of anthracnose in avocado

In recent years, anthracnose has become a significant disease affecting avocado fruit in the state of Michoacan, Mexico, where it significantly reduces fruit quality and commercial yield. Anthracnose has been assumed to involve Colletotrichum gloeosporioides and C. acutatum as causal agents. However, because of the increasing incidence of anthracnose, a more precise identification of the Colletotrichum spp. involved in this disease has become desirable. During the years 2004–2007, avocado fruits of different sizes exhibiting brown‐black and reddish spots on the pericarp and soft rot in the mesocarp, were gathered from orchards in nine counties. Fungal isolates were cultured on potato dextrose agar, and among these, 31 were selected for molecular, morphological and pathogenicity analyses. The molecular approaches used sequence typing of the internal transcribed spacer region and the partial nuclear large ribosomal subunit, allowing the unequivocal identification of C. gloeosporioides (71%), C. acutatum (16%) and C. boninense (13%). This last species has not been previously reported as being associated with anthracnose symptoms in avocado fruits anywhere in the world. Various morphological characteristics such as the size and shape of conidia were determined, as well as the conidial mass colour. Pathogenicity tests performed with all three species were conducted by inoculating healthy fruits. In each case, identical symptoms developed within 3 days of inoculation. Knowledge of the Colletotrichum populations in the Michoacan state, including the newly encountered avocado pathogen C. boninense, will facilitate further studies addressing the relationships between these Colletotrichum spp. and their avocado host.     

Colletotrichum species causing grape ripe rot disease in Vitis labrusca and V. vinifera varieties in the highlands of southern Brazil

Ripe rot is one of the most important bunch diseases of grapes in the highlands of southern Brazil and a matter of concern for winegrowers. Sixty-one strains isolated from berries of Vitis labrusca and V. vinifera varieties with symptoms were classified by phylogenetic analysis of the sequences of β-tubulin, glyceraldehyde-3-phosphate dehydrogenase, D1/D2 domain of 28S rDNA, and rDNA internal transcribed spacer. They were also characterized by morphology, and their pathogenicity was evaluated. The combined molecular data allowed identification of six Colletotrichum species: C. fructicola, C. kahawae and C. viniferum (gloeosporioides complex), C. limitticola, C. nymphaeae (acutatum complex), and C. karstii (boninense complex). This is the first report of C. karstii and C. limitticola associated with the ripe rot of grapes. Morphological characteristics varied within and among species, confirming their separation at the complex level. Pathogenicity tests on V. vinifera berries showed that the most prevalent species, C. viniferum (37.8%) and C. fructicola (36.1%), were more virulent than the less prevalent species C. limitticola and C. karstii. Our findings indicate that there is a high diversity of Colletotrichum species associated with ripe rot disease of grapes in Brazil. There were no clear differences in the distribution of Colletotrichum species between V. labrusca and V. vinifera varieties. The determination of fungal species responsible for grape ripe rot in Brazilian vineyards may contribute to further epidemiological studies and the development of more efficient prophylactic methods for ripe rot management.     

Field evaluation of systemic imidacloprid for the management of avocado thrips and avocado lace bug in California avocado groves

BACKGROUND: The efficacy of systemic applications of imidacloprid for the management of avocado thrips and avocado lace bug was determined in field trials. Following insecticide treatment by chemigation, leaves of appropriate age for each insect were sampled over a 6 month period and used for bioassays. Imidacloprid residues were measured by ELISA in leaves used for bioassays to determine concentrations of insecticide that were toxic to both pests. RESULTS: The uptake of imidacloprid into treated trees was extremely slow, peaking in the current year's leaf flush at only 8 ng cm^?2 leaf tissue after 15 weeks. Avocado thrips mortality in bioassays with young flush leaves, the preferred feeding substrate for this insect, was minimal, indicating that imidacloprid concentrations were below threshold levels needed for effective control. Residues present in older leaves, which are preferred by the avocado lace bug, were higher than in young flush leaves, and provided good control of this pest. Probit analysis of bioassay data showed that the avocado lace bug (LC₅₀ = 6.1 ng imidacloprid cm^?2 leaf tissue) was more susceptible to imidacloprid than the avocado thrips (LC₅₀ = 73 ng imidacloprid cm^?2 leaf tissue). CONCLUSIONS: In spite of the slow uptake of imidacloprid into avocado trees, the levels of imidacloprid would be sufficient to control avocado lace bug infestations. In contrast, the slow uptake would be problematic for avocado thrips control because inadequate levels of insecticide accumulate in new flush foliage and would allow avocado thrips populations to build to levels that would subsequently damage developing avocado fruit. Copyright © 2010 Society of Chemical Industry     

Pathogenicity of Colletotrichum species causing anthracnose of Capsicum in Asia

Anthracnose of chili is caused by a complex of Colletotrichum species, with recent surveys reporting at least 28 different species implicated. However, there have been very few studies to identify the relative pathogenicity of the various species or to optimize a bioassay to assess pathogenicity. A detached Capsicum fruit bioassay to determine the pathogenicity of a diverse geographical range of isolates of Colletotrichum scovillei showed fruit maturity, host genotype, and inoculation method all interact to affect infection and rate of lesion development. On Capsicum annuum ‘Bangchang’ fruit wounded prior to inoculation, pathogenicity was consistent regardless of fruit maturity. In contrast, without wounding there was variability in pathogenicity. On the relatively resistant host Capsicum chinense PBC932, pathogenicity was dependent on both the inoculation method and the maturity stage of the fruit. In addition, lack of correlation in pathogenicity of isolates between the two Capsicum lines indicated that there was host–isolate specialization that would make prediction of pathogenicity of isolates on host difficult. In a further study, 10 species of Colletotrichum isolated from diseased chili fruits in Asia caused anthracnose symptoms on C. annuum ‘Bangchang’ under all testing conditions, with large differences in aggressiveness. C. chinense PBC932 was generally more resistant to all the species, with smaller lesions produced in different host conditions. Colletotrichum javanense and C. scovillei were highly aggressive relative to other species, especially when inoculated on nonwounded fruit. Pathotype differences were identified within multiple isolates of C. scovillei and C. siamense, the two most frequently identified pathogenic species on chili.     

Evaluation of neonicotinoid, organophosphate and avermectin trunk injections for the management of avocado thrips in California avocado groves

BACKGROUND: Trunk injections of systemic insecticides were evaluated for the management of avocado thrips. Insecticide residues were quantified in leaves to determine when after treatment, and for how long, toxic concentrations of the insecticides were present. Residues in fruit were quantified to determine whether trunk injection of insecticides might present a greater risk than traditional application methods for contaminating fruit. RESULTS: Residues of imidacloprid and dinotefuran were at least tenfold higher in leaves when trees were treated via trunk injection compared with soil application. Dinotefuran uptake was more rapid than imidacloprid, and no residues were detected within fruit. Acephate was also mobilized very rapidly and gave good control of thrips in bioassays; however, residues of acephate and its insecticidal metabolite methamidophos were detected in the fruit for up to 4 weeks after injection. Avermectin uptake was very slow, and it was ineffective against avocado thrips. CONCLUSIONS: Trunk injections of acephate and dinotefuran permitted rapid uptake into avocados, and they are strong candidates as control methods for avocado thrips. However, residues of organophosphates in fruit could necessitate increased preharvest intervals. Residues of neonicotinoids were below detection limits in fruit, suggesting that neonicotinoids may be the more suitable control option of the two chemical classes. Copyright © 2012 Society of Chemical Industry     

Characterization and pathogenicity of Colletotrichum species associated with anthracnose on chilli (Capsicum spp.) in Thailand

Fungal isolates from chilli ( Capsicum spp.) fruits in Thailand that showed typical anthracnose symptoms were identified as Colletotrichum acutatum , C . capsici and C . gloeosporioides . Phylogenetic analyses from DNA sequence data of ITS rDNA and β-tubulin ( tub 2) gene regions revealed three major clusters representing these three species. Among the morphological characters examined, colony growth rate and conidium shape in culture were directly correlated with the phylogenetic groupings. Comparison with isolates of C . gloeosporioides from mango and C . acutatum from strawberry showed that host was not important for phylogenetic grouping. Pathogenicity tests validated that all three species isolated from chilli were causal agents for chilli anthracnose when inoculated onto fruits of the susceptible Thai elite cultivar Capsicum annuum cv. Bangchang. Cross-infection potential was shown by C . acutatum isolates originating from strawberry, which produced anthracnose on Bangchang. Interestingly, only C . acutatum isolates from chilli were able to infect and produce anthracnose on PBC 932, a resistant genotype of Capsicum chinense . This result has important implications for Thai chilli breeding programmes in which PBC 932 is being hybridized with Bangchang to incorporate anthracnose resistance into chilli cultivars.     

A new Fusarium lineage within the Gibberella fujikuroi species complex is the main causal agent of mango malformation disease in Brazil

Mango malformation is a serious disease in tropical and subtropical areas of the world and has been attributed to various Fusarium spp., including F. mangiferae , F. proliferatum , F. sacchari , F. sterilihyphosum and F. subglutinans . Isolates of Fusarium associated with mango malformation from Brazil, Egypt, India, South Africa and the United States were evaluated through amplified fragment length polymorphisms (AFLPs) and partial DNA sequences of the genes encoding β-tubulin ( tub2 ) and translation elongation factor 1-α ( tef1 ). These techniques were used to delimit species and to estimate the genetic and phylogenetic relatedness of the isolates. In the AFLP analysis, most of the Brazilian isolates formed a unique cluster. Additionally, one small cluster was formed by isolates of F. sterilihyphosum from Brazil and South Africa, and another by isolates of F. mangiferae from Egypt, India, South Africa and the United States. In the phylogenetic analysis, most of the Brazilian isolates represented a new phylogenetic lineage in the Gibberella fujikuroi species complex, where they formed a sister clade to F. sterilihyphosum. Representatives of both clades were pathogenic to mango (cv. Tommy Atkins) and Koch's postulates were completed for isolates belonging to the new lineage and to F. sterilihyphosum . Thus, most of the mango malformation disease in Brazil is due to a distinct phylogenetic lineage of Fusarium , and to a lesser extent by F. sterilihyphosum. The new phylogenetic lineage identified in this study, together with F. mangiferae and F. sterilihyphosum , are the only known taxa of Fusarium proven to be capable of causing mango malformation.     

Comparison of conventional and molecular methods for the detection of Rosellinia necatrix in avocado orchards in southern Spain

White root rot, caused by Rosellinia necatrix , is one of the most important diseases in avocado orchards and is particularly widespread on the Mediterranean seaboard of southern Spain. In this study, the presence of the pathogen in soil samples collected from the base of 47 plants showing different symptoms of canopy decline was assessed with a molecular detection method based on real-time Scorpion PCR. Results were compared with symptoms in the canopy and with the traditional method of isolation of R. necatrix from roots and/or bark. The fungus was isolated from 24 samples by the traditional method and from 37 soil samples by the molecular method (cycle threshold values 25·8 to 47·1), demonstrating the higher sensitivity and reliability of the molecular method. A single real-time PCR amplification was sufficient to detect R. necatrix in naturally infested soils. The avoidance of nested PCR has important practical implications because of the reduced costs and risk of cross contamination. Also, it enables faster sample analysis and is more appropriate for quantitative detection. A modified molecular method was also developed to detect R. necatrix in roots and in soils with very low populations of the pathogen.     

Molecular phylogeny and morphological characterization of the aetiological agent of sour rot on fruits and vegetables in Brazil

In Brazil, sour rot is an important postharvest disease on fruits and vegetables. Geotrichum candidum (synonym Galactomyces candidus) has been reported as the main species causing this disease. However, the identity of the causal agent is still uncertain. This research aimed to determine the identity of 165 fungal isolates associated with sour rot obtained from fruits and vegetables in Brazil, and to evaluate the effect of different temperatures on the incidence of sour rot on artificially inoculated tomato fruits. Based on the phylogenetic analyses of DNA sequences from the D1/D2 domain of the large subunit (LSU) rRNA gene and morphological analyses, 129 samples belonged to Galactomyces candidus, 15 to G. candidum var. citri-aurantii, 6 to G. phurueaense, 2 to Gal. pseudocandidus, 1 to Hyphopichia burtonii, 1 to H. khmerensis, 3 to Saccharomycopsis crataegensis, 1 to S. vini, 1 to Magnusiomyces tetrasperma, 1 to Trichosporon coremiiforme, and 1 to Zygoascus meyerae. Two new species were found, namely, Geotrichum solani (on potato) and Geotrichum spondiadis (on red mombin). All isolates were pathogenic when inoculated on healthy tomato fruits, including the new species of Geotrichum, which were also inoculated into their respective hosts, that is, potatoes and red mombins. To the best of our knowledge, this study is the first to report the presence of five other genera besides Geotrichum associated with sour rot on fruits and vegetables in Brazil, which demonstrates the diversity of fungi and yeasts associated with this disease.     

Population structure,pathogenicity, and fungicide sensitivity of Colletotrichum siamense from different hosts in Hainan,China

Areca palm, rubber tree, and coffee are always planted adjacent to each other or intercropped with each other, and Colletotrichum siamense was found to be the dominant species of Colletotrichum from these crops in Hainan, China. To study the population structure, pathogenicity, and fungicide sensitivity of C. siamense from these three crops in Hainan, isolates were first identified by their morphological characteristics and multilocus phylogeny. Then both permutational multivariate analysis of variance (PERMANOVA) and pairwise F_ST analysis showed that the original host and geographical origin (counties) had significant effects on genetic variation in the C. siamense population, explaining 5.6% and 16.3% of genetic variation, respectively. There were significant genetic differentiations between coffee and rubber tree populations but the genetic differentiation was small (F_ST = 0.04), while significant differentiations were observed among all populations from different counties except those between Haikou and Chengmai. Pathogenicity analysis using artificial inoculation showed that isolates had significantly higher disease incidence and diseased lesion diameter on wounded leaves than on nonwounded leaves. However, the original host of an isolate and geographical origin did not significantly affect the pathogenicity of the C. siamense populations from these three hosts. In vitro tests showed that there were no significant differences in the sensitivity of C. siamense populations to carbendazim, prochloraz, difenoconazole, and propiconazole from different original hosts and geographical origins. The present study suggests that host specialization of C. siamense has not occurred yet in coffee, rubber tree, and areca palm.     

Characteristics and distribution of Colletotrichum species in coffee plantations in Hainan,China

Anthracnose caused by Colletotrichum species is a serious disease on a range of economically important hosts. To determine the Colletotrichum species in coffee plantations in Hainan, China, 55 isolates were obtained from Coffea arabica (arabica) and C. canephora var. robusta (robusta) in five counties. Initially, partial sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were used to measure fungal genetic diversity. Then a subset of 23 isolates was selected to represent the range of genetic diversity, varieties and geographic origin for further multilocus phylogenetic analyses. These isolates belong to eight known Colletotrichum species from three Colletotrichum species complexes, including gloeosporioides (C. endophytica, C. fructicola, C. ledongense, C. siamense and C. tropicale), boninense (C. karstii), gigasporum (C. gigasporum), and one singleton species (C. brevisporum). Of these, C. siamense was isolated in all sampled counties and C. fructicola was identified in three counties. The other six species were isolated only in one or two counties. Only C. siamense and C. fructicola were isolated from arabica, whereas all eight species were isolated from robusta. Occurrence of C. brevisporum, C. endophytica, C. ledongense and C. tropicale in coffee has not been reported previously. Pathogenicity tests showed that all eight species were pathogenic to coffee leaves and fruit. In vitro tests showed that Colletotrichum isolates from coffee in Hainan were most sensitive to prochloraz, less sensitive to carbendazim, propiconazole and difenoconazole, and least sensitive to myclobutanil.     

Aetiology of anthracnose on grapevine shoots in Brazil

Anthracnose is an important disease in vineyards in south and southeast Brazil, the main grape‐producing regions in the country. This study aimed to identify the causal agents of grapevine anthracnose in Brazil through multilocus phylogenetic analyses, morphological characterization and pathogenicity tests. Thirty‐nine Elsinoë ampelina and 13 Colletotrichum spp. isolates were obtained from leaves, stems and berries with anthracnose symptoms collected in 38 vineyards in southern and southeastern Brazil. For E. ampelina isolates, the internal transcribed spacer (ITS), histone H3 (HIS3) and elongation factor 1‐α (TEF) sequences were analysed. HIS3 was the most informative region with 55 polymorphic sites including deletions and substitutions of bases, enabling the grouping of isolates into five haplotypes. Colonies of E. ampelina showed slow growth, variable colouration and a wrinkled texture on potato dextrose agar. Conidia were cylindrical to oblong with rounded ends, hyaline, aseptate, (3.57–) 5.64 (?6.95) μm long and (2.03–) 2.65 (?3.40) μm wide. Seven species of Colletotrichum were identified: C. siamense, C. gloeosporioides, C. fructicola, C. viniferum, C. nymphaeae, C. truncatum and C. cliviae, with a wide variation in colony and conidium morphology. Only E. ampelina caused anthracnose symptoms on leaves, tendrils and stems of Vitis vinifera and V. labrusca. High disease severity and a negative correlation between disease severity and shoot dry weight were observed only when relative humidity was above 95%. In this study, only E. ampelina caused anthracnose symptoms on grapevine shoots in Brazil.     

Infection of Nicotiana species by the anthracnose fungus, Colletotrichum orbiculare

Colletotrichum gloeosporioides f. sp. malvae, isolate Biomal®, ATCC 20767, was originally isolated from round-leaved mallow (Malva pusilla) and developed as a weed biocontrol agent. Ribosomal DNA sequence analysis was recently used to re-classify this fungus as C. orbiculare, which is an aggregate species with a number of formae speciales. Several morphological features of ATCC 20767 were examined that were consistent with those described for C. orbiculare, and inoculation of a number of Nicotiana species and several cultivars of N. tabacum showed that this fungus was pathogenic to many of these previously undescribed hosts. Spore germination and appressorium formation were higher on tobacco than previously observed on round-leaved mallow. The pathogen produced melanized appressoria on N. tabacum leaves that formed preferentially at the anticlinal epidermal cell wall. A symptomless phase of infection persisted for 72–96 h postinoculation, during which time the fungus first produced a spherical infection vesicle from an infection peg, and then large primary hyphae which grew through the epidermal cells. The large primary hyphae were highly constricted at the points of penetration of the host cell walls. Thin secondary hyphae appeared at 96–120 h postinoculation coinciding with the appearance of light green, water-soaked spots and the formation of acervuli. The infection of tobacco by C. orbiculare ATCC 20767 is not a non-specific interaction but appears to follow an intracellular hemibiotrophic infection process that is very similar to that established for the C. orbiculare infection of round-leaved mallow, cucurbits and beans.     

Fusarium rot of melon is caused by several Fusarium species

Fusarium rot of melon, caused by species of the genus Fusarium, has become an important postharvest disease for many Brazilian producers. Due to the delayed onset of symptoms, this disease is often only detected when fruits arrive at the importing country, thus generating economic loss for the exportation of the fruit. This study was developed with the aim of investigating which Fusarium species cause fruit rot in melon and to evaluate any differences in aggressiveness and development of symptoms. Species were identified through phylogenetic analysis of two loci and morphological markers. The 28 isolates obtained from diseased melon fruits of different commercial cultivars were identified as Fusarium falciforme (FSSC), F. sulawesiense, F. pernambucanum (FIESC), and F. kalimantanense (FOSC). Three isolates belong to a new phylogenetic lineage within the F. fujikuroi species complex (FFSC). All isolates were tested for pathogenicity, and first symptoms of rot in Canary melon were observed 2 days after inoculation. Isolates of F. falciforme and F. sulawesiense were shown to be more aggressive. Our results extend information on Fusarium species that cause fruit rot in melon and support the development of management strategies, as there is currently no efficient control for this disease. To our knowledge, this is the first report of the occurrence of species of the FSSC, FOSC, and FFSC from muskmelon fruits in Brazil.     

Factors influencing biological traits and aggressiveness of Colletotrichum species associated with cashew anthracnose in Brazil

Anthracnose is the main fungal disease on cashew orchards in Brazil, occurring on both vegetative and reproductive organs of cultivated and noncultivated host plants. Understanding the effect of physical and chemical exogenous factors on the biological traits of Colletotrichum spp. and determining their host range are key to developing appropriate anthracnose control measures. The present study aimed to estimate the optimum temperatures for mycelial growth, sporulation, and conidial germination of seven Colletotrichum species (C. chrysophilum, C. fragariae, C. fructicola, C. gloeosporioides, C. queenslandicum, C. siamense, and C. tropicale) associated with cashew anthracnose in Brazil. Their aggressiveness on cashew leaves and six alternative host fruits, and their sensitivity to three fungicides were also investigated. The optimum temperatures for mycelial growth, sporulation, and conidial germination ranged from about 25 to about 33°C. All Colletotrichum species induced anthracnose symptoms on wounded cashew leaves, but none of them caused lesions on intact leaf surfaces. The Colletotrichum species, except for C. fragariae and C. fructicola, were pathogenic to wounded fruits of avocado, banana, guava, mango, and papaya, and some isolates also produced lesions on nonwounded fruit tissues. No symptoms were observed on passion fruits, regardless of the inoculation method. Mycelial growth, sporulation, conidial germination, and/or appressorial formation of the seven Colletotrichum species were inhibited by azoxystrobin, difenoconazole, and thiophanate-methyl to varying degrees. The present study will contribute to the development of forecasting models based on prevailing weather of cashew cropping zones and improve cashew anthracnose management in Brazil.     

Plasma-activated water inhibits in vitro conidial germination of Colletotrichum alienum,a postharvest pathogen of avocado

Cold plasma, an ionized gas produced by applying an electrical current to air, can be used to produce plasma-activated water (PAW), which has excellent antimicrobial properties. In this study PAW was applied to conidia of Colletotrichum alienum to investigate its impact on conidial germination in vitro. PAW was produced by treating tap, deionized, or distilled water with cold plasma for 30 or 60 min to produce PAW30 or PAW60, each of which was then incubated for up to 24 hr with a conidial suspension of C. alienum in a ratio of 1:1, 1:2, or 1:3 (conidial suspension:PAW), and the percentage germination measured. The greatest reduction in germination occurred when conidia were incubated with PAW60 produced from deionized water or distilled water, for all ratios. For PAW30, deionized water was the most effective for all three ratios, and on this basis, deionized water was selected for all further experiments. PAW produced from smaller volumes of water and at shorter distances from the cold plasma source was more effective at reducing germination. Treatment of conidia with acidified water was not as effective as PAW at inhibiting germination. Nitrates and nitrites were present in the PAW in varying concentrations and may have contributed to the inhibition of germination. PAW retained activity and reduced germination even after storage for 15 days. These findings demonstrate the potential of PAW as a novel treatment for postharvest fungal pathogens.     

Screening of weed extracts for antifungal properties against Colletotrichum lagenarium,the causal agent of anthracnose in cucumber

The antifungal activity of the leaf extracts from 203 weed species was investigated by performing a bioassay using cucumber plants and Colletotrichum orbiculare. The leaf extracts from four families, namely, Urticaceae, Onagraceae, Commelinaceae, and Solanaceae, showed a relatively stronger inhibition of the anthracnose lesions in cucumber plants when compared with the other families investigated in the study. A remarkable inhibition of anthracnose infection in cucumber leaves was observed with the extracts from the following 19 weed species: Boehmeria nipononivea and Boehmeria longispica, Persicaria scabra, Ranunculus japonicus and Ranunculus sceleratus, Cardamine flexuosa, Oenothera biennis, Aeschynomene indica, Indigofera pseudo‐tinctoria, Torilis scabra, Calystegia japonica, Solanum americanum, Bidens pilosa, Gnaphalium japonicum, Kalimeris yomena, Bromus catharticus, Cynodon dactylon, Alopecurus aequalis, and Scirpus tabernaemontani. In particular, it is noteworthy that the extracts from C. dactylon, K. yomena, and S. americanum completely inhibited anthracnose infection in cucumber.     

The effect of climatic factors on Colletotrichum gloeosporioides, causal agent of mango anthracnose, in the Philippines

The epidemiology of the anthracnose pathogen of mango, Colletotrichum gloeosporioides, was studied over two growing seasons in the Philippines. This pathogen spreads within tree canopies as water-borne conidia during rainfall, and causes symptoms on young flush leaves, flowers and fruit. Infection studies with leaves and fruit incubated at different temperatures and humidities led to the derivation of a logistic regression model of the percentage of conidia forming appressoria. This model was compared with a similarly derived model from work in Australia; it appeared that the Philippine isolates of C. gloeosporioides were adapted to the higher mean temperatures of the Philippines. Conidia were observed to germinate and form appressoria at relative humidities (RH) between 95 and 100%, even though free surface moisture was only visible at 100% RH. This model was used retrospectively to estimate infection levels in two field trials which had been established to compare pre- and post-harvest practices in the control of the disease. Using this information to plan applications of a curative fungicide might have resulted in four fewer sprays in the first trial and one less in the second, compared with the standard protective spray programme employed.