Occurrence of bacterial rot of onion caused by Bacillus amyloliquefaciens in Korea

In 2008, bacterial rot on onion bulbs (Allium cepa L.) was observed in several low-temperature warehouses in Changnyeong-gun, Korea. The causal pathogen was isolated and identified as Bacillus amyloliquefaciens based on morphological and biochemical characterization and sequence analysis of its genome. The isolated bacteria caused the same rot symptom on inoculated onion bulbs as found in naturally infected onions during storage and was reisolated from these bulbs. This is the first report of bacterial rot of onion caused by B. amyloliquefaciens in Korea.     

Determination of seedborne fungi in Onion and their transmission to Onion sets

Samples of onion (Allium cepa L.) seeds were obtained from seven regions in Turkey. The seed coat, embryo and endosperm were cultured, the seedborne fungi were determined and their transmission to onion sets was investigated in both sterile and field soils. Among the fungi determined,Aspergillus alutaceus Berk, and Curt.,Beauveria bassiana (Bals.) Vuill.,Cladosporium cladosporioides (Fres.) de Vries,Geotrichum sp.,Humicola fuscoatra Traaen,Trichoderma harzianum Rifai andT. pseudokoningii Rifai in onion seeds, andFusarium culmorum (W.G.Sm.) Sacc,F. graminearum Schwabe andF. sambucinum Fuckel in onion sets, were recorded for the first time.Aspergillus niger v. Tieghem was found at the highest rate in seed samples (especially in the seed coat), and in bulbs and roots of onion sets that developed from these seeds, whether in sterile or field soil.Fusarium oxysporum Schlecht was isolated at a higher rate from onion sets grown in sterile or field soil, than from seeds.F. acuminatum Ellis and Everhart,F. sambucinum, F. equiseti (Corda) Sacc. andF. graminearum were isolated only from onion sets grown in sterile soil. In dual culture tests, theseFusarium isolates were inhibited byA. niger and thus, exceptfor F. oxysporum, could not develop in agar plate. TheFusarium spp. appeared in onion-sets grown in sterile soil and were inhibited by other fungi in field soil. It was concluded that all fungi were seedborne and thatA. niger andFusarium spp., but not the other fungi, were transmitted from the seeds to onion sets.A. niger andF. oxysporum were also transmitted through the soil.     

Studies on Botrytis spp. occurring on onions (Allium cepa) and leeks (Allium porrum)

Botrytis byssoidea (mycelial neck rot) was more prevalent than B. allii (sclerotial neck rot) on the leaves of field onions and the bulbs of stored onions grown in some of the areas where onions or onions and leeks had previously been grown sequentially.
B. byssoidea and B. porri were also isolated from leeks. Spores of B. allii, B. byssoidea (from onions and leeks), B. porri , and B. squamosa caused infection of seedlings of salad (green) and bulb onions.
Inoculation with B. squamosa spores caused severe infection of seedling leaves, but inoculation with mycelial discs caused little damage to onion bulb tissue. By comparison, mycelial discs of the remaining species were highly pathogenic to bulbs.
The practical implications of disease transfer of certain of these species between onions and leeks are discussed.     

Biological control ofBotrytis cinerea in residues and flowers of Rose (Rosa hybrida)

Microbial isolates from living petals, petal residues and leaf residues of rose, and from laboratory collections, were evaluated for control ofBotrytis cinerea in rose. In leaf residues artificially infested withB. cinerea, isolates of the filamentous fungiGliocladium roseum, FR136 (unidentified) andTrichoderma inhamatum reduced sporulation of the pathogen by >90%, other filamentous fungi were 25–90% effective, and those of yeasts and bacteria were <50% effective. In artificially inoculated petal residues, no microbe reduced sporulation ofB. cinerea by >75%, but isolates ofCladosporium oxysporum and four yeasts were 51–75% effective, and three filamentous fungi, eight yeasts andBacillus subtilis isolates were 26–50% effective. Isolates ofT. inhamatum, C. oxysporum andG. roseum performed best againstB. cinerea among isolates evaluated in leaf residues naturally infested with the pathogen and indigenous microorganisms. Totals of ten isolates of filamentous fungi (includingC. oxysporum andC. cladosporioides), two of yeasts and five ofBacillus subtilis completely prevented lesion production byB. cinerea in detached petals, and a further six isolates of filamentous fungi (includingG. roseum) and six yeasts were 90–99% effective. Isolates ofC. oxysporum, C. cladosporioides andB. subtilis, the most effective microorganisms againstB. cinerea in flower buds, reduced number of lesions in the range of 42–65% compared with 59–89% for à standard fungicide (vinclozolin). It is suggested that application of leading antagonists Jo living rose leaves and flowers should optimize control of inoculum production byB. cinerea when the tissues die. Optimal biocontrol of lesion production in flower buds requires a better understanding of the microenvironment of petals.     

Control of infection and sporulation ofBotrytis cinerea on bean and tomato by saprophytic bacteria and fungi

Sixty isolates of saprophytic microorganisms were screened for their ability to reduce the severity of grey mould (Botrytis cinerea) infection and sporulation. Isolates of the bacteriaXanthomonas maltophilia, Bacillus pumilus, Lactobacillus sp., andPseudomonas sp. and the fungusGliocladium catenulatum reduced germination of conidia of the pathogen and controlled disease on bean and tomato plants. Their activity under growth room conditions was good, consistent, and similar to the activity of the known biocontrol agent,Trichoderma harzianum T39 (non-formulated). Although the tested isolates may for nutrients with the germinating conidia ofB. cinerea, resistance induced in the host by live or dead cells were also found to be involved. Inhibitory compounds were not detected on treated leaves. Sporulation ofB. cinerea after its establishment on leaves was also reduced by the above mentioned isolates and byPenicillium sp.,Arthrinium montagnei, Ar. phaeospermum, Sesquicillium candelabrum, Chaetomium globosum, Alternaria alternata, Ulocladium atrum, andT. viride. These sporulation-inhibiting fungi did not reduce the infection of leaves byB. cinerea. Most of these selected fungi and bacteria were capable of reducing lesion expansion.     

Effects of postharvest onion curing parameters on bulb rot caused by Pantoea agglomerans,Pantoea ananatis and Pantoea allii in storage

Crop loss of onion bulbs during storage carries an exceptionally high economic impact because a large portion of the production expenses has been expended before storage. Because of this, it is important to define practices that can reduce onion bulb losses caused by storage rots. This study investigates the impact of various curing parameters on disease development resulting from infection by Pantoea agglomerans, P. ananatis and P. allii on onion bulb cultivars Vaquero and Redwing, during storage. Overall, both the incidence and mean rot severity were similar amongst the bulbs under comparable conditions regardless of the species of Pantoea inoculated, although a significant difference was detected between the two onion bulb cultivars. In addition, a significant reduction of storage rot was observed when curing temperatures were ≤35°C. At temperatures >35°C, a shorter curing duration (2 days vs 14 days) decreased the severity of bulb rot due to Pantoea. This increased understanding of the inter‐relationships between the parameters used for curing, and the incidence and severity of bulb rot caused by Pantoea helps provide guidance towards using the curing process as a means to reduce the level of damage resulting from post‐harvest storage rot.     

Fusarium oxysporum,F. proliferatum and F. redolens associated with basal rot of onion in Finland

In recent years in Finland, Fusarium infections in onions have increased, both in the field and in storage, and Fusarium species have taken the place of Botrytis as the worst pathogens causing post‐harvest rot of onion. To study Fusarium occurrence, samples were taken from onion sets, harvested onions and also from other plants grown in the onion fields. Isolates of five Fusarium species found in the survey were tested for pathogenicity on onion. Fusarium oxysporum was frequently found in onions and other plants, and, of the isolates tested, 31% caused disease symptoms and 15% caused growth stunting in onion seedlings. Fusarium proliferatum, a species previously not reported in Finland, was also identified. Over 50% of the diseased onion crop samples were infected with F. proliferatum, and all the F. proliferatum isolates tested were pathogenic to onion. Thus, compared to F. oxysporum, F. proliferatum seems to be more aggressive on onion. Also some of the F. redolens isolates were highly virulent, killing onion seedlings. Comparison of the translation elongation factor 1α gene sequences revealed that the majority of the aggressive isolates of F. oxysporum f. sp. cepae group together and are distinct from the other isolates. Incidence and relative proportions of the different Fusarium species differed between the sets and the mature bulbs. More research is required to determine to what extent Fusarium infections spoiling onions originate from infected onion sets rather than the field soil.     

The persistence of Botrytis allii in field soil

Neck rot ( Botrytis allii ) affected bulbs of onions for 2 successive years when these were grown either in the field in soil from which an infected crop had been cleared 6 months previously or when infected debris was incorporated into field soil 6 months before the first crop was sown. These sources did not continue to cause infection of onion crops grown on the contaminated areas in the four succeeding years.
The white storage tissue of onion bulbs (healthy or infected) persisted for less than 6 months in unsterile field soil contained in pots while sclerotia present in similar soil varied in their rate of decay but lost their capacity to produce conidiophores of B. allii after 6 months. In one sample, sclerotia were not recovered after 5 months; Gliocladium roseum , a mycoparasite, was present in this sample and may have affected survival.     

Induction of resistance to Sclerotium rolfsii in different varieties of onion by inoculation with Trichoderma asperellum

We evaluated the ability of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg to induce resistance to the fungal plant pathogen, Sclerotium rolfsii Saccardo, in three onion (Allium cepa L.) varieties. Both the severity of disease and the activities of glucanase, chitinase and peroxidase (enzymes involved in plant resistance) were evaluated in onions inoculated with T. asperellum alone, S. rolfsii alone, or both T. asperellum and S. rolfsii (dual-inoculation) and compared to uninoculated (control) plants. In dual inoculations, the presence of T. asperellum reduced the severity of disease symptoms caused by S. rolfsii. Inoculation with T. asperellum alone increased glucanase, chitinase and peroxidase activity in bulbs, roots and leaves of all three onion varieties compared to uninoculated controls; bulbs of the variety Red Satan (RS) had the highest enzyme activity. In plants inoculated with S. rolfsii alone, enzyme activity was only increased in bulbs and roots compared to uninoculated controls. The highest levels of enzyme activity also occurred only in bulbs and roots of plants that had been dual-inoculated with T. asperellum and S. rolfsii. Plants of the RS variety showed the highest enzyme activities (both constitutive and induced) and showed the lowest severity of disease. Therefore, application of T. asperellum has potential as a biological control alternative to synthetic fungicides for protection of onion crops against infection by S. rolfsii. This protection depends on both constitutive and induced defence responses and varies amongst onion varieties.     

Disease resistance in Vicia faba and Phaseolus vulgaris

Droplets of spore suspensions of each of four isolates ofBotrytis cinerea but not those of each of four isolates ofB. fabae proved to contain an antifungal compound 24 h after application on pod tissue ofVicia faba. Partial inhibition of germ-tube growth of three highly pathogenic isolates ofB. fabae was caused at 2.5 times the concentration of inhibitor needed to cause similar inhibition of each isolate ofB. cinerea and a weakly pathogenic isolate ofB. fabae. After extraction, concentration and chromatographic separation, 5–10 times more inhibitor was obtained from lesions in pods caused byB. cinerea than from those caused byB. fabae. However, the amounts of inhibitor extracted from whole leaves bearing either large lesions caused byB. fabae or small lesions caused byB. cinerea were almost the same. It is suggested that infection by either fungus induces inhibitor formation, but thatB. fabae metabolizes the inhibitor to an inactive form.No relation was found between amounts of an inhibitor produced in droplets of spore suspensions 24 h after application on pods of differential varieties ofPhaseolus vulgaris and the disease reactions caused by races ofColletotrichum lindemuthianum. Each race appeared to have a similar sensitivity to the inhibitor. Anatomical studies showed that only superficial growth of germ-tubes occurred in seed cavities in the first two days, after which penetration took place. Resistant or susceptible reactions were distinguished after 6 days in young pods, and even later in old pods. Before rejecting the hypothesis that the inhibitor may have a role in the mechanism of disease resistance, amounts of inhibitor in and around infection sites on leaves or stems should be measured. Apparent protection of leaf areas against infection was caused by prior inoculation with a race which was avirulent on the leaf. This phenomenon is consistent with the action of an inhibitor of the type found in pod tissues, but could be caused by reactions as yet unknown.     

Storability of onion bulbs contaminated by<Emphasis Type="Italic">Aspergillus niger</Emphasis> mold

In the course of pre- and postharvest epidemiological studies on bulbs contamination byAspergillus niger, two Sudanese onion cultivars were tested: ‘Saggai Red’ and ‘El-Hilo White’.A. niger spores, whether seedborne, soilborne or airborne, were avirulent to the healthy growing onion plants. The fungus heavily contaminated the dead onion tissues, mainly the dead leaves followed by the dry scales, the dead roots and, to a lesser extent, the bulb necks, preferring the red-skinned cultivar to the white one. The initial spores carried from naturally contaminated field soil on the dead tissues could germinate and produce massive numbers of new spores on bulbs stored at average climatic conditions of Sudan (23–39°C, 29–93% relative humidity). Under laboratory-controlled conditions, optimal growth occurred at 75–85% r.h. on bulbs with dry scales and maximum losses occurred at 100% r.h. and ambient temperature. Underin vitro conditions, the optimal growth and sporulation temperature forA. niger was in the range of 30–35°C. Early harvesting and removal of the dead onion tissues improved bulb storability in aseptic stores under low temperature and relative humidity conditions. http://www.phytoparasitica.org posting Oct. 20, 2003.     

A survey of mold flora and of the mycotoxin deoxynivalenol in corn imported to ISRAEL

Shipments of corn imported to Israel from the U.S.A. during 1985 were sampled during unloading and examined for the presence of fungi and the trichothecene deoxynivalenol (DON). The most frequent species found on the corn wasAspergillus flavus followed byA. versicolor; three otherAspergilli — A. niger, A. ochraceus andA. fumigatus — were found at a much lower frequency. DON analysis was performed by electron capture detection gas chromatography after derivatization with heptafluorobutyryl imidazole. At fortification levels of 0.1, 1 and 2 μg/g, recoveries of 80—100% were obtained. Although DON was not detected in any of the samples analyzed, the observation (in the shipments) of fungi belonging to the generaFusarium andAspergillus suggests a potential danger of mycotoxin contamination. The relatively high moisture content of the samples increased the likelihood of such a hazard.     

Effect of temperature of production of Botrytis allii conidia on their pathogenicity to harvested white onion bulbs

Botrytis allii colonies incubated at low temperatures have been reported to produce larger conidia that germinate faster and give rise to longer germ-tubes than those grown at room temperature. The present study compared the effect of conidia produced at 20°C and at 0 and –2°C on their pathogenicity to artificially inoculated white onion bulbs, and the effect of conidial concentration (5×10³ and 5×10⁴ conidia/mL) on disease incidence, lesion area, incubation and latent period during storage at 20, 5 and 0°C. At all storage temperatures and periods tested conidia produced at −2°C caused a higher disease incidence and larger areas of rot than those produced at higher temperatures. When the conidial production temperature was raised to 20°C, the duration of incubation on the bulbs inoculated with 5×10⁴ conidia/mL was more than doubled during storage at 0°C, tripled at 5°C, and took 50% longer at 20°C. The incubation period was not significantly affected by conidial concentration at 20°C, and only slightly at 5 and 0°C, but at low temperatures the latent period was longer because of the delay induced in sporulation. These data are consistent with the packers' opinion that cross-infection of spring onions by long-term refrigerated onions in grading lines caused earlier and heavier rotting.     

Comparative abilities of fungi pathogenic and nonpathogenic to bean (Phaseolus vulgaris) to metabolize phaseollin

The abilities of fungi pathogenic and nonpathogenic to bean (Phaseolus vulgaris) to metabolize the phytoalexin phaseollin were compared when grown in shake cultures containing 12 to 15 μg phaseollin/ml. Under these conditions phaseollin was metabolized by five out of seven pathogens and by three out of five nonpathogens. Disappearance of phaseollin was accompanied by the appearance of metabolic products in cultures ofFusarium solani f. sp.phaseoli, Colletotrichum lindemuthianum, Botrytis cinerea andCladosporium herbarum. The nonpathogenC. herbarum detoxified phaseollin to 1a-hydroxyphaseollone as rapidly as the pathogenF. solani f.sp.phaseoli. Phaseollin was converted to 6a-hydroxyphaseollin by the pathogensB. cinerea andC. lindemuthianum, and this product was further metabolized by the latter fungus. 6a-Hydroxyphaseollin was less fungitoxic toB. cinerea. C. lindemuthianum was equally sensitive to both compounds. Phaseollin was not metabolized by the pathogensFusarium oxysporum f. sp.phaseoli andThielaviopsis basicola.     

Auftreten und Nachweis von Fusarium oxysporum und F. proliferatum an Steck- und Saatzwiebeln

The pathogen Fusarium oxysporum f. sp. cepae inducing the Fusarium basal rot mainly spreads in warmer cultivation regions due to its adaptibility to high temperature. Meanwhile the pathogen occurs in Germany as well, especially in years with relatively high average temperature during the growing season. Phytopathological investigations of 300 symptomless onion bulbs showed a contamination rate of approximately 10% with regard to Fusarium spp, with F.?oxysporum proving to be the predominant species. Onion sets planted in these fields were latently infected with F.?oxysporum at rates of 19?C98%. Unexpectedly, the contaminated sets did not indispensably lead to a high occurrence of plants exhibiting characteristic symptoms of Fusarium basal rot such as wet and dry rot. Presumably, the development of symptoms is particularly affected by given climatic conditions. The results of pathogenicity tests of isolated Fusarium spp. isolates under controlled conditions support this assumption. The inoculation of the substrate with selected Fusarium spp. isolates resulted in a reduction of emergence by up to 70% under controlled conditions, which are suboptimal with regard to the cultivation of onions. The emergence of plants was not affected by Fusarium spp. under optimal cultivation of onions. However, under optimal cultivation conditions a reduction of plant growth occurred in a subsequent growth stage. Beside F.?oxysporum, F.?proliferatum could be detected in onion bulbs as well as seeds. The proportion of contaminated seeds accounted to 62%. Both species F.?oxysporum and F.?proliferatum proved to be pathogenic in onion although their isolates varied much in their virulence.     

Effects of temperature,relative humidity and age of conidia on the incidence of spotting on gerbera flowers caused by Botrytis cinerea

In recent years, spotting of ray florets of gerbera flowers has become an important problem. This type of small necrotic lesions may occur before, but especially shortly after harvesting the flowers.Botrytis cinerea was easily isolated from such lesions. Inoculation withB. cinerea only gave typical necrotic lesions, when dry conidia were dusted on the flowers with a short period of high rh after inoculation. At 18–25 °C a high rh for at least 5 hours was necessary. Rotting of ray florets and receptacles byB. cinerea occurred when inoculated flowers were kept wet for a few days. Spots consist of one to several necrotic, usually epidermal cells. A single conidium could give rise to a necrotic lesion after germination. Germination of conidia and lesion formation occurred between 4 and 25 °C; at 30 °C, germination and lesion formation did not occur. Between 18 and 25 °C, many lesions became visible within 1 day after inoculation; at 4 °C it took 2 to 3 days before lesions could be seen. If kept dry, conidia ofB. cinerea remained ungerminated on ray florets of gerbera flowers and could be removed from the ray florets. Within 1 day at high rh, germination occurred and lesions were produced. Conidia ofB. cinerea, stored dry, were able to survive much longer than the lifetime of a gerbera flower. Even after storage at room temperature for up to 14 months, some conidia were able to germinate in vitro and on ray florets and induce the formation of lesions. Addition of gerbera pollen diffusate stimulated germination and lesion formation.     

Survival of dicarboximide-resistant strains ofBotrytis cinerea in plant debris during summer in Israel

Survival- ofBotrytis cinerea was monitored during two summer seasons. Mycelium and conidia were found dead on the surface of plant debris within 2 months of incubation, whereas a high level of viability was detected in thallus of the pathogen which was 1–2 mm inside the dry host tissue. Of the 148 samples of infected senescing cucumber female fruits, 8% survived seven warm months; half of these isolates ofB. cinerea were resistant to dicarboximides (5 (μ/ml iprodione). Of the stems of cucumber infected withB. cinerea in winter, 18% yielded the pathogen at the beginning of the following winter; 15% of the surviving isolates were resistant to dicarboximides. Cucumber seedlings artificially infected byB. cinerea did not yield the pathogen longer than 9 weeks after establishment of infection, even when incubated in the shade. Plant debris with symptoms of gray mold were kept in the shade during the summer; at the beginning of winter it was possible to establish infection ofB. cinerea from the dry debris.     

Volatile Metabolite Profiling for the Discrimination of Onion Bulbs Infected by Erwinia carotovora ssp. carotovora, Fusarium oxysporum and Botrytis allii

The volatile metabolites of the headspace gas of onion bulbs inoculated with three different pathogens, Erwinia carotovora ssp. carotovora, Fusarium oxysporum and Botrytis allii, were profiled using gas chromatography/mass spectrometry. Differences in the number and amount of volatile metabolites were observed. Two hundred and fifty three volatile metabolites were detected in bulbs inoculated with three pathogens or sterile distilled water. On day three, 202 volatile metabolites were observed, compared to 166 on day six. Of the 253 compounds, however, only 59 occurred relatively consistently over replications, of which 25 compounds were specific to one or more pathogens, including 10 that were unique to a pathogen. Metabolites such as 1-Oxa-4,6-diazacyclooctane-5-thione and 4-mercapto-3-(methylthio)--(thio-lactone)-crotonic acid were exclusive to onions inoculated with F. oxysporum. Acetone, acetic acid-hydrazide, propylcarbamate, 1-bromo-1-propene, thiirane, 1-(methylthio)-E-1-propene and 1-ethenyl-4-ethyl-benzene were specific to B. allii. 3-bromo-furan was specific to E. carotovora ssp. carotovora. Sterile water-inoculated bulbs produced 3,3-dioxy-1,2-propanediol-tetranitrate. Highest amount of sulfurs was found in pathogen-inoculated, while highest amounts of terpenes, aromatics and aliphatics were found in sterile distilled water-inoculated bulbs. The possible use of these differences in the volatile metabolites for detecting and discriminating diseases of onion in storage is discussed.     

Biological control ofBotrytis cinerea on tomato stem wounds withTrichoderma harzianum

The effectiveness ofTrichoderma harzianum in suppression of tomato stem rot caused byBotrytis cinerea was examined on tomato stem pieces and on whole plants. Ten days after simultanous inoculation withB. cinerea andT. harzianum, the incidence of infected stem pieces was reduced by 62–84%, the severity of infection by 68–71% and the intensity of sporulation by 87%. Seventeen days after inoculation of wounds on whole plants, the incidence of stem rot was reduced by 50 and 33% at 15 and 26 °C, respectively, and the incidence of rot at leaf scar sites on the main stem was reduced by 60 and 50%, respectively. Simultanous inoculation and pre-inoculation withT. harzianum gave good control ofB. cinerea (50 and 90% disease reduction, 10 days after inoculation). The rate of rotting was not reduced by the biocontrol agent once infection was established. However, sporulation byB. cinerea was specifically reduced on these rotting stem pieces. Temperature had a greater effect than vapour pressure deficit (VPD) on the efficacy of biocontrol. Suppression ofB. cinerea incidence byT. harzianum on stem pieces was significant at 10 °C and higher temperatures up to 26 °C. Control of infection was significantly lower at a VPD of 1.3 kPa (60% reduction), than at VPD<1.06 kPa (90–100% control). Reductions in the severity of stem rotting and the sporulation intensity of grey mould were generally not affected by VPD in the range 0.59–1.06 kPa. Survival ofT. harzianum on stems was affected by both temperature and VPD and was greatest at 10 °C at a low VPD and at 26 ° C at a high VPD.     

Effect of aerated compost tea on grapevine powdery mildew, botrytis bunch rot and microbial abundance on leaves

Aerated compost tea (ACT), prepared from immature compost, was applied to foliage and fruit of grapevines (Vitis vinifera) to assess its potential for suppressing two important diseases: botrytis bunch rot, caused by Botrytis cinerea, and powdery mildew, caused by Erysiphe necator. An ACT applied to leaves of Cabernet Sauvignon vines in pots 7 days before inoculation with E. necator conidia reduced mean powdery mildew severity on the three youngest expanded leaves (at inoculation) to less than 1 %; mean severity on non-treated, inoculated leaves was 15 %. Multiple applications of ACTs at two vineyards in different growing seasons suppressed powdery mildew to <1 % mean severity on Chardonnay leaves (non-treated 79 % severity) and bunches (non-treated 77 % severity), and on Riesling leaves (non-treated 24 % severity). The same treatments reduced the incidence of Chardonnay bunches with latent B. cinerea and Riesling bunches with sporulating B. cinerea, although the level of botrytis bunch rot in both experiments was not economically damaging. The numbers of culturable bacteria, fungi and yeasts on Chardonnay leaves were higher than pre-treatment levels 10 days after ACT application, as were fungal numbers on Riesling leaves 21 days after treatment. Suppression by ACTs of two fruit and foliar pathogens of grapevine with different biology and epidemiology indicated potential for their use as a tactic in integrated disease management. Further testing of ACTs in a range of viticultural environments and application regimes will contribute to a better understanding of the impact of this tactic on disease, grape and wine quality.