Antisporulant Activity Research Articles

Mycosynthesis of highly fluorescent selenium nanoparticles from Fusarium oxysporum, their antifungal activity against black fungus Aspergillus niger, and in-vivo biodistribution studies.

In the past few years, photo-luminescent inorganic materials have been studied extensively as fluorescent sensors, and diagnostic and bioimaging tools. The assessment of photoluminescence (PL) properties of selenium nanoparticles (Se NPs), especially mycosynthesized Se NPs, is still in its infancy. Herein, we have biosynthesized highly dispersed fluorescent Se NPs (42 nm) using endophytic fungus Fusarium oxysporum, and fully characterized them using sophisticated instruments like TEM, XRD, UV–Vis spectrophotometer, FTIR, and PL spectrometer. To determine the therapeutic efficacy and side effect profiles, these crystalline Se NPs were radiolabeled with technetium-99m (99mTc) and their biodistribution and renal clearance times were investigated in the normal Wister rat. The results showed that these Se NPs may be useful for targeting the lungs and liver dysfunction as significant accumulation of these NPs was observed in the liver (approx. 19.47 ± 4%) and lungs (at 6 ± 1%) after 10 min of post-injection. Quick circulation and the presence of Se NPs in kidney (3.8 ± 2%) also suggested the easy excretion of these NPs from the body through urinary tract. Furthermore, the antioxidant activity of Se NPs (IC50, 159.5 μg/mL) has been investigated using DPPH free radical scavenging assay with scavenging efficacy of 80.4% where ascorbic acid (IC50, 5.6 μg/mL) was used as a positive control. Additionally, the microscopic study of the inhibition zone encircled around Se NPs confirmed their strong antifungal and antisporulant activity against the black fungus Aspergillus niger.

Unveiling the antisporulant activity of mycosynthesized gold-selenide nanoparticles against black fungus Aspergillus niger

Gold-selenide (AuSe), a transition metal chalcogenide, has become a highly-promising material in electronics and other technologies due to its stable 2D layered structure with ultrahigh carrier mobilities. Recently, these unexplored micro-particles have been synthesized by chemical routes in inert nitrogen or argon atmosphere. To flourish new applications at a low cost to the environment, it is of prime importance to develop a novel, eco-friendly, energy-effective, economical bio-approach for the synthesis of AuSe NPs as environmentally sustainable biological routes are free from the use of toxic chemicals owing considerable importance in biomedical science. Herein, we for the first time report an endophytic fungus Fusarium oxysporum assisted green approach for the mycosynthesis of AuSe NPs at the ambient atmospheric conditions and unveiled their anti-sporulant activity against the black fungus Aspergillus niger. The biosynthesized, crystalline AuSe NPs with an average particle size of 52 nm have been fully characterized using sophisticated instruments while the microscopic study confirmed its high anti-sporulation potency against Aspergillus niger. As the spore germination is completely suppressed without affecting mycelial growth by the selective inhibition of conidiophores and conidiation, the hyphal length and mycelial morphology of various filamentous fungi can be controlled to increase the industrial productivities. At a time when the widespread use of antifungal agents increases antifungal drug resistance, our biosynthesized AuSe NPs (anti-sporulant) will minimize the risk of re-infection and will find major applications in developing new fungicide or drugs at extremely cost-efficient means and in abundant quantities.

Curative Fungicide Activity Against Calonectria pseudonaviculata, the Boxwood Blight Pathogen1

Abstract Azoxystrobin, azoxystrobin plus benzovindiflupyr, kresoxim-methyl, propiconazole, pyraclostrobin, pyraclostrobin plus fluxapyroxad, tebuconazole, tetraconazole, thiophanate-methyl, and triflumizole fungicides were evaluated for curative and anti-sporulant activity against boxwood blight caused by Calonectria pseudonaviculata on detached leaves and whole boxwood plants (Buxus spp.). Pretreating detached leaves with 30 or 300 ppm a.i. 24 h prior to inoculation reduced disease compared to the untreated control for all fungicides. Fungicides were also applied 24 to 96 h post-inoculation. Only propiconazole reduced diseased leaf incidence to at least half of the control. When leaves were treated post-infection with 300 ppm propiconazole, tetraconazole, tebuconazole, or triflumizole, the pathogen did not sporulate over 2 wks. Propiconazole also reduced the percent of leaf area diseased; lesions were nearly 80% smaller with 300 ppm applied 48 h after inoculation. ‘True Dwarf' boxwood plants treated with 450 ppm thiophanate-methyl, 120 ppm pyraclostrobin or 150 ppm propiconazole 48 h after inoculation demonstrated that only propiconazole reduced the number of diseased leaves, blight lesions and the frequency of pathogen re-isolation. Experiments with ‘Green Mound' and ‘Green Mountain' boxwood cultivars and additional fungicides applied 48 h after inoculation demonstrated that propiconazole at 300 ppm, pyraclostrobin plus fluxapyroxad (150 ppm each) and azoxystrobin (135 ppm) plus benzovindiflupyr (67.5 ppm) reduced disease. Index words: fungicide management, Buxus, chemical disease management Chemicals used in this study: azoxystrobin (Heritage 50 WG), azoxystrobin plus benzovindiflupyr (Mural 30, 50 WG), kresoxim-methyl (Cygnus 50 WG), propiconazole (ProCon-Z 14.3 L), pyraclostrobin (Insignia 20 WG), pyraclostrobin plus fluxapyroxad (Orkestra Intrinsic 21.26 SC), tebuconazole (Torque 38.7 SC), tetraconazole (Minerva 11.6 SC), thiophanate-methyl (3336 50% WP), triflumizole (Procure 480 SC). Species used in this study: boxwood (Buxus L.), boxwood blight (Calonectria pseudonaviculata (Crous, J.Z. Groenew. & C.F. Hill) L. Lombard, M. J. Wingf. & Crous.

Contribution of Mid-Season Cover Sprays to Management of Peach Brown Rot at Harvest.

Four protectant fungicides applied as midseason cover sprays were quantitatively assessed for their ability to reduce brown rot caused by Monilinia fructicola during the preharvest fruit ripening periods in the 2012 through 2015 growing seasons. No fungicides were applied during bloom or during the preharvest period. Treatment programs consisted of captan, sulfur, ziram, and thiram applications beginning at early shuck-split stage and ending with the final cover spray at 23 to 26 days before harvest. The incidence of brown rot at harvest was determined by examining 41 to 91 fruit for symptoms of rot on each of four replicate trees for each treatment. The incidence of sporulating blossom blight cankers was assessed during the preharvest period at 8, 15, and 22 days after the final cover spray. An in vivo bioassay was also conducted at 7, 14, and 21 days after the final cover spray to ascertain the level of fungicide residue during the preharvest period. The bioassay uses conidia germination as a quantitative indicator of effective residue. Results of the harvest assessment showed that captan cover sprays significantly reduced brown rot incidence in all years of the study. Furthermore, results of the bioassay demonstrated that fungicide residue was the mechanism by which this control occurred. None of the other fungicide cover spray programs contributed significantly to brown rot control at harvest in any year, and bioassay results showed insufficient residue to inhibit conidial germination. Antisporulant activity against blossom blight cankers was not observed for any fungicide program, indicating that reducing inoculum production from this source was not a mechanism for brown rot control. The captan and sulfur programs provided very good control of peach scab incidence and severity, caused by Fusicladium carpophilum, while the ziram and thiram programs failed to control this disease. These findings demonstrated that captan cover sprays can contribute significantly to control of brown rot at harvest, thereby augmenting the efficacy and consistency of management by preharvest fungicide programs. Furthermore, any reduction of the M. fructicola population by the captan cover sprays should reduce selection pressure against the site-specific fungicides commonly used during the preharvest period, thereby prolonging their useful life for brown rot control.

Isolation, identification and in vitro screening of grapevine yeasts for the control of black aspergilli on grapes

Antagonistic yeasts were isolated from the surface of grape berries cv. “Cabernet sauvignon” and “Maratheftiko” from six vineyards in Cyprus and identified at species level using molecular methods. The identification revealed that the yeast isolates belonged to seven taxonomically distinct groups: Aureobasidium pullulans, Cryptococcus magnus, Hanseniaspora uvarum, Candida zeylanoides, Candida sake, Rhodotorula mucilaginosa and Pseudozyma aphidis. A total of 55 yeast isolates were evaluated in a preliminary screening test on agar to select isolates exhibiting inhibition against an ochratoxigenic strain of Aspergillus tubingensis. Thirty-three yeast isolates were selected for their antisporulant activity on A. tubingensis and their ability to reduce the growth of fungal mycelium. These isolates were assayed by a detached berry test for their ability to inhibit infection by the ochratoxigenic strain of A. tubingensis. Twenty-eight yeast isolates belonging to three species, namely 25 isolates of A. pullulans, 2 isolates of C. magnus and 1 isolate of C. sake, reduced the A. tubingensis colonization of grape berries. The highest antagonistic activity was shown by the A. pullulans isolates, with biocontrol efficacies ranging between 17.1% and 95.7%. The results of this study suggest that antagonist yeasts potentially effective for biological control of A. tubingensis on grape can be found among the microbiota associated with grape berries in Cyprus vineyards.

Influence of Trifloxystrobin on Primary Inoculum and Progression of Scab Epidemics on Stone Fruit.

The ability of the QoI fungicide trifloxystrobin to reduce production of conidia by Fusicladium carpophilum on twig lesions was quantitatively assessed over a 3-year period from 2005 through 2007. Four annual treatment programs, consisting of two consecutive trifloxystrobin applications at pink + bloom, bloom + petal fall, and petal fall + shuck-split, plus a single application timing at petal fall, were examined in a 'Redgold' nectarine orchard harboring high levels of overwintering scab lesions. Sporulation potential, the ability of twig lesions to produce conidia under optimum environmental conditions, was subsequently assessed five to six times during each spring and early summer. In each year of the study, all four treatments significantly reduced the area under the sporulation curve or peak sporulation. The petal fall + shuck-split program provided the greatest antisporulant activity, reducing conidia production at peak sporulation by 82 to 92%. Furthermore, examination of results over the 3-year period showed that the programs significantly slowed the annual rate of increase in peak sporulation; however, none of the programs completely halted or caused a decline in the annual rate. Although no fungicide was applied after the treatment programs, results from fruit disease assessments showed that these programs, applied as much as 3 months earlier, significantly reduced disease incidence and, in particular, disease severity. A comparison of four QoI fungicides in 2008 indicated that trifloxystrobin and azoxystrobin provided the most control of fruit scab, while pyraclostrobin + boscalid and fluoxastrobin yielded minimal or no benefit. Results of this study demonstrate that certain QoI fungicides, in particular trifloxystrobin and azoxystrobin, can probably improve the efficacy of current protectant programs used for peach scab control by providing season-long control of F. carpophilum sporulation on twig lesions. Such program enhancement may be critical when orchards have high inoculum levels and/or environmental conditions are very favorable to disease development.

Effect of QoI Fungicides on Colonization and Sporulation of Monilinia fructicola on Peach Fruit and Blossom Blight Cankers.

Three studies were conducted to examine the curative activity of azoxystrobin, trifloxystrobin, and pyraclostrobin + boscalid against Monilinia fructicola, causal agent of brown rot on peach. In the first study, 'Autumnglo' peach trees were treated with each of the three fungicides both before and after fruit inoculation. In the second study, the effects of fungicide active ingredient, rate/volume, and inoculation timing were examined on inoculated 'Suncrest' peach fruit. Results of these studies showed that sporulating area, on average across all treatments, was reduced by 15.9, 42.4, and 0.4% for azoxystrobin, trifloxystrobin, and pyraclostrobin + boscalid, respectively. In any single treatment, trifloxystrobin provided the greatest benefit with two consecutive sprays, reducing sporulating area by 53 to 60%. In contrast to sporulation activity, the three fungicides exhibited less of an inhibitory effect on fruit colonization. When applied at maximum labeled rates in the various treatments, azoxystrobin, trifloxystrobin, and pyraclostrobin + boscalid reduced colony growth, on average, by 12.3, 7.5, and 7.4%, respectively. Because the pathogen was inoculated into the mesocarp, this low level of activity against colonization may be due to a lack of deeper systemic movement of the fungicides into fruit tissue. In the final study, the three fungicides were examined for their antisporulant activity on blossom blight twig cankers. Unlike results observed on fruit, significant reductions in spore production on cankers were observed for all three fungicides. Azoxystrobin, trifloxystrobin, and pyraclostrobin + boscalid provided 56, 71, and 53% reductions, respectively, in the number of conidia produced per unit canker length. Overall results of these studies indicated that quinone outside inhibitor fungicides, in addition to their known protectant activity, also possess varying levels of curative activity against M. fructicola. In particular, trifloxystrobin demonstrated good antisporulant activity on both fruit infections and cankers.

Antisporulant Activity of Watery Extracts of Plants against Sclerospora graminicola Causing Downy Mildew Disease of Pearl Millet

Watery extracts of forty plant species commonly growing in across India have been screened for antisporulant activity against Sclerospora graminicola (Sacc.) Schroet., the causative agent of pearl millet downy mildew. The collection represented 38 genera of 30 families. The extracts of thirteen species did not show any effect, whereas the activity of extracts of Allium sativum, Clematis gouriana, Evolvulus alsinoides, Mimusops elengi, Parthenium hysterophorus, Piper nigrum and Tagetes erecta were commensurable to that of marketed botanical fungicides and Mikal 70 wp. The crude extracts of 12 species (Agave americana, Aloe vera, Artemisia parviflora, Citrus limon, Citrus sinensis, Eucalyptus globosus, Euphorbia hirta, Leucas aspera, Murraya koenigi, Ocimum sanctum, Santalum album and Zingiber offinale) completely inhibited the zoosprorangium formation while in the case of remaining 8 plants the crude extracts reduced only partially the sporulation. The antisporulant activity of commercialised Azadirachta preparation (Nutri-Neem) was more pronounced than that of Reynutria based one (Milsana) and Sabadilla (veratrin), however, these botanical preparations held off synthetic fungicides and the most active watery extracts.

DEVELOPMENTAL STAGE RESP ONSE OF PE ARL MILLET DOWNY MILDEW (SCLEROSPO RA GRAMINICOLA) TO FUNGICIDES

Inhibitory effect of 21 commercial and 6 experimental fungicides was assessed in model experiments against pearl millet downy mildew disease. Chemicals differed strongly by their anti-mildew activity, however neither the pathogen nor the host plant showed complete tolerance to any of compounds tested. Nevertheless, the plants outgrew depressant effect of compounds observed in germling stage and this activity did not significantly influence the yield. There was a significant correlation between yield performance and disease inhibitory effects assessed either in vitro or in vivo tests. The response of pathogen to investigated compounds varied during ontogeny, where zoosporangium formation was found to be the most sensitive ontogenetic event. When comparing responses of pathogen and host with fungicides by means of principal component analysis, the presence of two independent components has been demonstrated accounting for 86% of the total variation to which responses of host and pathogen contributed differently. The antisporulant activity of compounds evaluated on detached leaf segments and their positive effect on yield significantly correlated allowing to predict the expectable grain yield significantly (p>0.05). Beside acylanilides andoprim, drazoxolon and efosit offered efficacy on the level requested. Metalaxyl and tridemorph as well as andoprim and cymoxanil acted synergistically against S. graminicola.

Management of tomato leaf mould caused by Cladosporium fulvum with trifloxystrobin

The protective, curative and eradicant activity of the strobilurin fungicide trifloxystrobin against Cladosporium fulvum on tomatoes was determined under growth chamber and greenhouse conditions. In growth chamber experiments chlorothalonil applied at 100 μg ml −1 was used as standard fungicide treatment. Seven-week-old tomato plants, hybrid Alma F1, were inoculated by conidial suspension. Protective treatments were carried out by spraying plants 24, 48 and 96 h before inoculation at the doses of 5, 10 and 20 μg a.i. ml −1. Curative treatments were carried out with the same doses, at the same time intervals after inoculation. Additionally, spray treatments were applied after the appearance of the symptoms to evaluate the anti-sporulant activity of the fungicides tested. Protective treatments of trifloxystrobin applied 24 and 48 h before inoculation provided disease control higher than 88% at all the application doses tested, while only the dose of 20 μg a.i. ml −1 was highly effective when applied 96 h before the inoculation of the plants (IOP). The curative treatments were less effective than the protective treatments. Post-inoculation treatments of trifloxystrobin at 10 or 20 μg ml −1 were efficacious only when applied 24 or 48 h after IOP, with limited activity when applied 96 h after inoculation. Eradicant treatments of trifloxystrobin provided satisfactory anti-sporulant activity when applied at the dose rate of 20 μg ml −1. Applications of trifloxystrobin at the rates of 5 or 7.5 g a.i. 100 l −1 of spray solution carried out during a 2-year period (2004–2005), in the greenhouse, demonstrated the validity of the above findings, providing control efficacy values higher >90%. Moreover, during both years of the study, applications of trifloxystrobin either at 5 or 7.5 g a.i. 100 l −1, reduced spore production significantly on diseased tomato leaves. The results of the study showed that trifloxystrobin may play a crucial role as part of an integrated chemical control programme for tomato leaf mould caused by C. fulvum.

Antisporulant Activity of Watery Extracts of Plants against Sclerospora graminicola Causing Downy Mildew Disease of Pearl Millet

Antisporulant Activity of Watery Extracts of Plants against Sclerospora graminicola Causing Downy Mildew Disease of Pearl Millet

Response of pearl millet downy mildew ( Sclerospora graminicola ) to diverse fungicides

The inhibitory effect of 15 commercial and five experimental fungicides was assessed both in greenhouse and field experiments against Sclerospora graminicola, the causative agent of pearl millet downy mildew disease. Chemicals differed in anti-mildew activity. However, neither the pathogen nor the host plant was completely tolerant to any compounds tested. The plants depressed by fungicides in the germling stage recovered until formation of inflorescence, so this activity did not significantly influence grain yield. There was a significant correlation between antisporulant activity of compounds evaluated on detached leaf segments and their positive effect on yield performance. All compounds increased the grain yield of downy mildewed pearl millet when applied in the maximum doses tolerated by pearl millet. However, analysis of the cost-return budget showed that disease control < 30% is uneconomic. Fungicides of the acylanilide series exhibited the highest protective effect (over 95%) and andoprim, drazoxolon and efosit were also effective.

Antisporulant activity of leaf extracts of Indian plants against Sclerospora graminicola causing downy mildew disease of pearl millet

Methanolic extracts of forty plant species commonly growing across India were collected and have been screened for antisporulant activity against Sclerospora graminicola (Sacc.) Schroet., the causative agent of pearl millet downy mildew. The collection represented 38 genera of 30 families. The methanolic extracts of nine species did not show any effect, whereas the activity of the extracts of Clematis gouriana, Evolvulus alsinoides, Mimusops elengi, Allium sativum and Piper nigrum were commensurable to that of the marketed botanical fungicides. The extracts of 11 species (Agave americana, Artemisia pallens, Citrus sinensis, Dalbergia latifolia, Helianthus annus, Murraya koenigii, Ocimum basilicum, Parthenium hysterophorus, Tagetes erecta, Thuja occidentalis and Zingiber offinale) exhibited remarkable antisporulant effect even after 10-fold dilution of the crude extracts while in the case of remaining 15 plants the crude extracts loosed activity after 10-fold dilution. The antisporulant activity of commercialised Azadirachta preparation (Nutri-Neem) was more pronounced than that of Reynutria based one (Milsana) and Sabadilla (veratrin), however, these botanical preparations held off the extracts of C. gouriana and E. alsinoides and synthetic fungicides.

Biological activity and physical modes of action of the Qo inhibitor fungicides trifloxystrobin and pyraclostrobin against Cercospora beticola

The effect of trifloxystrobin and pyraclostrobin on spore germination and mycelial growth of Cercospora beticola, were determined in vitro. In addition, the protective, curative, translaminar and post-symptom activity against the pathogen was determined on sugar beet plants in growth chambers with difenoconazole and chlorothalonil as standard fungicide treatments. Both pyraclostrobin and trifloxystrobin were highly active causing complete inhibition of spore germination at concentrations of 0.01 and 0.1μgml−1, respectively, although higher concentrations were required for complete inhibition of fungal growth. Both fungicides were protective against C. beticola when applied 96h and 24h before inoculation of plants. Both fungicides, applied at 20μgml−1 , were superior to difenoconazole applied at 10μgml−1 and to chlorothalonil applied at 100μgml−1. Effective control was obtained when strobilurin fungicides were applied 24h after inoculation, but were less effective at 96h after inoculation. Pyraclostrobin at 20μgml−1 applied 96h after inoculation, was more effective than difenoconazole while control with trifloxystrobin at 20μgml−1 applied 96h after inoculation was similar to that obtained with difenoconazole. Chlorothalonil showed little activity against C. beticola in curative treatments. Tests to evaluate translaminar activity showed that disease severity on leaves treated with strobilurin fungicides on the upper leaf surface and inoculated on the opposite surface was similar to that obtained on leaves treated and inoculated on the same surface. Anti-sporulant activity was good with both strobilurin fungicides applied at concentrations of 10 or 20μgml−1 when applied after the appearance of the symptoms. The anti-sporulant activity of difenoconazole was similar to that of pyraclostrobin and trifloxystrobin applied at 5μgml−1, while chlorothalonil did not provide significant antisporulant activity. Such results encourage the evaluation of trifloxystrobin and pyraclostrobin under field conditions to select optimal partner fungicides for use in mixtures.

Protective, Curative and Eradicant Activity of the Strobilurin Fungicide Azoxystrobin against Cercospora beticola and Erysiphe betae

AbstractThe protective, curative and eradicant activity of the strobilurin fungicide azoxystrobin against Cercospora beticola and Erysiphe betae on sugar beet was determined under growth chamber conditions. Difenoconazole and chlorothalonil were used as standard fungicides against C. beticola, while chlorothalonil was replaced by sulphur against E. betae. Fungicides were applied before (protective treatments) and after (curative treatments) inoculation at 24, 48 and 96 h intervals, respectively. An additional spray treatment was applied after the appearance of the symptoms to evaluate the eradicant activity of the fungicides tested. Applications of azoxystrobin at 16 μ/ml provided 89–94% and 95–97% disease control against C. beticola and E. betae, respectively. Curative treatments of azoxystrobin either at 8 or 16 μg/ml provided control of Cercospora leaf‐spot higher than 90% only when it was applied 24 h after inoculation of the plants. Comparatively, chlorothalonil (100 μg/ml) provided satisfactory control of C. beticola when applied in protective treatments (83–87% disease control) but showed little activity when applied after the inoculation of the seedlings (45–76% disease control). High control efficacy against E. betae was also obtained by protective applications of sulphur (600 μg/ml) but the fungicide failed to provide satisfactory disease control, particularly when applied for 48 or 96 h after inoculation of seedlings. Difenoconazole (8 μg/ml) gave excellent protective and curative activity against both pathogens. Eradicative treatments with azoxystrobin provided high antisporulant activity of 94–96% and 85–93% against C. beticola and E. betae, respectively. Similarly, high antisporulant activity was also provided by difenoconazole, while postsymptom applications of chlorothalonil and sulphur provided significantly lower antisporulant activity against C. beticola and E. betae, respectively. Such results encourage the evaluation of azoxystrobin under field conditions to determine optimal treatment schedules and to select possibly partner fungicides for use in mixtures.

Comparative Physical Modes of Action of Azoxystrobin, Mancozeb, and Metalaxyl Against Plasmopara viticola (Grapevine Downy Mildew)

The physical modes of action of azoxystrobin, mancozeb, and metalaxyl were evaluated on grapevine seedlings using Plasmopara viticola as a model pathogen. The protectant, postinfection, postsymptom, translaminar, and vapor activities of azoxystrobin were evaluated at a rate of 250 μg/ml. Azoxystrobin provided 100% disease control when applied 1 to 5 days before inoculation. Postinfection applications of azoxystrobin had little effect on the incidence of disease, but colony area and sporulation from the resultant lesions was reduced by 47 and 96%, respectively, relative to the check treatment when applied up to 5 days after inoculation. Postsymptom applications (6 days after inoculation) of azoxystrobin resulted in an 85% mean reduction of resporulation from diseased tissue relative to the check when seedlings were evaluated 1 to 14 days after treatment. Translaminar activity was greatest when the upper surface of the leaf was treated 7 days before inoculation of the lower leaf surface (94% disease control). In contrast, control was <50% when leaves were similarly inoculated 1 and 3 days after treatment. Vapor activity was not pronounced, providing maximum reductions of 5, 11, and 37%, with regard to incidence, colony area, and sporulation, relative to the check when seedlings were treated 1 to 7 days before inoculating adjacent, untreated leaves. Comparatively, mancozeb (1,790 μg/ml) provided complete control of the disease when applied 1 to 5 days before inoculation, but showed little postinfection activity in reducing disease incidence, although it exhibited moderate to high antisporulant activity when applied in postinfection and postsymptom modes (mean reductions of 38 and 89%, respectively, compared with the check treatments). Metalaxyl (260 μg/ml) also provided complete control of the disease when used in protectant mode, and also when applied 1 day after inoculation. Applications at 3 to 5 days after inoculation provided substantial reductions in disease severity and sporulation (mean reductions of 46 and 94%, respectively, compared with the check treatments), and postsymptom applications resulted in a mean 84% reduction in resporulation. Collectively, the results of this study illustrate the unique physical modes of action for azoxystrobin in comparison to that of two traditional protectant and systemic fungicides, and provide information on how azoxystrobin and other strobilurin fungicides with similar physical modes of action should be best used in disease management programs.

Quantitative aspects of the antisporulant activity of imazalil, an agricultural fungicide

AbstractA new technique for collecting aerial conidiating parts of Penicillium italicum was used to study the action of imazalil as an antisporulant. In spite of its very low vapor pressure, imazalil reached the target site–‐the aerial hyphae–‐via the vapor phase. Using 14C‐labelled imazalil it was found that uptake proceeded very rapidly, reaching concentrations of 2 to 3.8 μg imazalil per g fresh weight of aerial mycelium within 24 hr. This amount caused alterations, both in the morphology of the hyphae and in ergosterol biosynthesis.

Observations on the antisporulant activity of imazalil (enilconazole)

AbstractImazalil, incorporated in a solid nutrient medium, had no effect on the sporulation of Penicillium italicum at concentrations that did not strongly inhibit mycelial growth. However, when the fungus was grown submerged in liquid culture, sporulation of P. italicum appeared to be more affected than vegetative growth; at 33 nM, imazalil completely prevented the formation of penicilli without adverse effects on growth. Imazalil was able to prevent sporulation in the vapour phase as shown by scanning electron microscopy on P. italicum and Aspergillus niger; the vapours of the compound were found to affect different stages of the sporulation process, depending on the timing of the experiment. Thus, in order to show antisporulant activity, imazalil had to reach the target site by means other than migration within the fungus.

Glasshouse tests of fungicides for apple powdery mildew control. II. Eradicant and anti-sporulant activity

SummarySmall apple plants with sporulating mildew colonies were sprayed with fungicide. The numbers of spores produced after treatment were taken as a measure of the eradicative and anti-sporulant activity of each fungicide. Eight of the materials tested greatly reduced sporulation in the nine days following treatment, but three had very little effect. Bupirimate, pyrazophos, binapacryl and ditalimfos were the most active fungicides tested. An overall rating for the activity of the fungicides against mildew is given.

Antisporulant activity of chemicals towards fungi causing cankers on apple branches

SUMMARYSix antisporulant compounds, selected from 120 chemicals screened against Gloeosporium fructigenum in vitro, were applied to lesions on Cox apple shoots caused by Nectria galligena or G. perennans. In the following 11 months, 42 and 33% fewer spores were trapped from N. galligena cankers treated with 2,4,5,6‐tetrachlorophenol or benomyl respectively, and 87 and 71% fewer from G. perennans cankers treated with 8‐hydroxyquinoline or benomyl respectively, compared with those caught from untreated cankers. Miscible tar‐petroleum oil had an antisporulant effect equal to that of benomyl on both N. galligena and G. perennans.